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1. Shard Calculation

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Calculated Shard: 63 (from laksa076)

2. Crawled Status Check

Query:

curl -X POST \
  'http://laksa063.int.ahrefs:8124/' \
  -H 'Content-Type: text/plain' \
  -H 'X-ClickHouse-Database: crawler3' \
  -H 'Authorization: Basic YXBpOg==' \
  -d 'SELECT getAhrefsURLFromUnparsed(src_unparsed) AS found_url, ifNull(toUnixTimestamp(download_stamp), 0) AS crawl_time, ifNull(toUnixTimestamp(props_url_first_seen), 0) AS first_indexed_time, download_http_code AS http_code, src_unparsed AS src_unparsed, src_root_hash AS src_root_hash, history_drop_reason AS history_drop_reason, meta_title AS meta_title, meta_descriptions AS meta_descriptions, attrs_boilerpipe_text AS attrs_boilerpipe_text, attrs_markdown AS attrs_markdown, attrs_readable_markdown AS attrs_readable_markdown, meta_canonical AS meta_canonical FROM crawler3.page_info_local FINAL PREWHERE (src_root_hash, src_unparsed) IN ((getAhrefsRootHashFromUnparsed(getAhrefsUnparsedNoserviceFromURL(\'https://www.build-electronic-circuits.com/current-limiting-resistor/\')), getAhrefsUnparsedNoserviceFromURL(\'https://www.build-electronic-circuits.com/current-limiting-resistor/\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/","crawl_time":1775881271,"first_indexed_time":1497848496,"http_code":200,"src_unparsed":"com,build-electronic-circuits!www,\/current-limiting-resistor\/ s443","src_root_hash":"10912690570910736463","history_drop_reason":null,"meta_title":"Current Limiting Resistor","meta_descriptions":["A current limiting resistor is often used to control the current going through an LED. Learn how to select the right resistor value and type."],"attrs_boilerpipe_text":"A current limiting resistor is a resistor that is used to reduce the current in a circuit.\nA simple example is a resistor in series with an LED.\nYou would usually want to have a current limiting resistor in series with your LED so that you can control the amount of current through the LED.\nIf too much current is going through your LED, it will burn out too fast. If too little current is going through it, it might not be enough to lit the LED.\nCalculating the necessary resistor value\nCheck the datasheet of your component to find voltage drop and the appropriate current for your LED.\nIf you can’t find a datasheet, you can test it.\nConnect the LED and a resistor in series to a variable voltage source. Start at 0 volts and increase the voltage gradually until the LED lit up.\nMeasure the voltage over the LED and the current going through.\n10 Simple Steps to Learn Electronics\nElectronics is easy when you know what to focus on and what to ignore. Learn what \"the basics\" really is and how to learn it fast.\nLet’s say the LED needs 15 mA and has a voltage drop of 2 volts. You have a 5 V power source that you would like to power it with. Which resistor value do you need?\nTo find the resistor value, we start with finding the voltage drop over the resistor. Since there is a 2 volt drop over the LED, there will be a 3V drop over the resistor.\nOk, so we have 3V and we want to have 15 mA going through the resistor and the LED.\nTo find the necessary resistor value we use\nOhm’s law\n.\nthis gives us\nSo the necessary value for the current limiting resistor is 200 Ohms.\nChoosing the right resistor\nSo you know that you need a 200 Ohm resistor.\nBut when you look for components you find that there are several different\ntypes of resistors\n.\nWell, the only thing you need to be aware of is the wattage rating of the component. How much effect can the resistor handle?\nSo you need to figure out how much effect that will be dissipated in your resistor.\nTo find this you use the following formula for calculating power\nIt states that power equals the current multiplied with the voltage. So we get\nThis means your resistor must be able to handle at least 45 mW.\nUsually, most resistors handle from 250 mW and up, so it will be easy to find a suitable resistor.\nReturn from Current Limiting Resistor to Electronic Schematics\nMore Resistors Tutorials\n10 Simple Steps to Learn Electronics\nElectronics is easy when you know what to focus on and what to ignore. Learn what \"the basics\" really is and how to learn it fast.","attrs_markdown":"![fbpx](https:\/\/www.facebook.com\/tr?id=165977292002783&ev=PageView&noscript=1)\n\n[Skip to content](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#content \"Skip to content\")\n\n[![Build Electronic Circuits](https:\/\/www.build-electronic-circuits.com\/wp-content\/uploads\/2023\/09\/Logo-WP-500px.png)](https:\/\/www.build-electronic-circuits.com\/)\n\nMenu\n\nMenu\n\n- [Tutorials]()\n  - [555 Timer](https:\/\/www.build-electronic-circuits.com\/555-timer\/)\n  - [Arduino](https:\/\/www.build-electronic-circuits.com\/what-is-arduino\/)\n  - [Basic Electronics](https:\/\/www.build-electronic-circuits.com\/basic-electronics\/)\n  - [Capacitors](https:\/\/www.build-electronic-circuits.com\/how-does-a-capacitor-work\/)\n  - [Circuit Building](https:\/\/www.build-electronic-circuits.com\/how-to-build-circuits\/)\n  - [Circuits & Projects](https:\/\/www.build-electronic-circuits.com\/category\/circuits\/)\n  - 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[555 Timer](https:\/\/www.build-electronic-circuits.com\/555-timer\/)\n  - [Arduino](https:\/\/www.build-electronic-circuits.com\/what-is-arduino\/)\n  - [Basic Electronics](https:\/\/www.build-electronic-circuits.com\/basic-electronics\/)\n  - [Capacitors](https:\/\/www.build-electronic-circuits.com\/how-does-a-capacitor-work\/)\n  - [Circuit Building](https:\/\/www.build-electronic-circuits.com\/how-to-build-circuits\/)\n  - [Circuits & Projects](https:\/\/www.build-electronic-circuits.com\/category\/circuits\/)\n  - [Digital Electronics](https:\/\/www.build-electronic-circuits.com\/category\/digital-electronics\/)\n  - [Diodes](https:\/\/www.build-electronic-circuits.com\/what-is-a-diode\/)\n  - [Electronic Components](https:\/\/www.build-electronic-circuits.com\/basic-electronic-components\/)\n  - [KiCad](https:\/\/www.build-electronic-circuits.com\/kicad-tutorial\/)\n  - [Learn Electronics](https:\/\/www.build-electronic-circuits.com\/how-to-learn-electronics\/)\n  - [Light-Emitting Diodes](https:\/\/www.build-electronic-circuits.com\/what-is-an-led\/)\n  - [Logic Gates](https:\/\/www.build-electronic-circuits.com\/logic-gates\/)\n  - [Microcontrollers](https:\/\/www.build-electronic-circuits.com\/what-is-a-microcontroller\/)\n  - [PCB Design](https:\/\/www.build-electronic-circuits.com\/pcb-design\/)\n  - [Power Supplies](https:\/\/www.build-electronic-circuits.com\/linear-power-supply\/)\n  - [Repair Electronics](https:\/\/www.build-electronic-circuits.com\/learn-to-repair-electronics\/)\n  - [Resistors](https:\/\/www.build-electronic-circuits.com\/what-is-a-resistor\/)\n  - [Schematic Diagrams](https:\/\/www.build-electronic-circuits.com\/electronic-schematics\/)\n  - [Soldering](https:\/\/www.build-electronic-circuits.com\/how-to-solder\/)\n  - [Transistors](https:\/\/www.build-electronic-circuits.com\/how-transistors-work\/)\n  - [4000 Series IC](https:\/\/www.build-electronic-circuits.com\/4000-series-integrated-circuits\/)\n  - [7400 Series IC](https:\/\/www.build-electronic-circuits.com\/7400-series-integrated-circuits\/)\n- [Electronics Courses](https:\/\/ohmify.com\/ \"Academy with courses for learning electronics\")\n- [About Me](https:\/\/www.build-electronic-circuits.com\/about\/)\n- [Contact](https:\/\/www.build-electronic-circuits.com\/contact\/)\n\n# Current Limiting Resistor\nOctober 21, 2022\n\nSeptember 9, 2013\n\nby [Øyvind Nydal Dahl](https:\/\/www.build-electronic-circuits.com\/author\/oyvind\/ \"View all posts by Øyvind Nydal Dahl\")\n\nA current limiting resistor is a resistor that is used to reduce the current in a circuit.\n\nA simple example is a resistor in series with an LED.\n\n![fi-simplest-circuits](https:\/\/www.build-electronic-circuits.com\/wp-content\/uploads\/2013\/09\/fi-simplest-circuits.jpg)\n\nYou would usually want to have a current limiting resistor in series with your LED so that you can control the amount of current through the LED.\n\nIf too much current is going through your LED, it will burn out too fast. If too little current is going through it, it might not be enough to lit the LED.\n\n## Calculating the necessary resistor value\n![A current limiting resistor in series with an LED](https:\/\/www.build-electronic-circuits.com\/wp-content\/uploads\/2013\/09\/current-limiting-resistor-with-led.png)\n\nCheck the datasheet of your component to find voltage drop and the appropriate current for your LED.\n\nIf you can’t find a datasheet, you can test it.\n\nConnect the LED and a resistor in series to a variable voltage source. Start at 0 volts and increase the voltage gradually until the LED lit up.\n\nMeasure the voltage over the LED and the current going through.\n\n![ebook cover](https:\/\/www.build-electronic-circuits.com\/wp-content\/uploads\/2024\/04\/Learn-Electronics-Cover-2023-cropped-heavily.png)\n\n## 10 Simple Steps to Learn Electronics\nElectronics is easy when you know what to focus on and what to ignore. Learn what \"the basics\" really is and how to learn it fast.\n\nLet’s say the LED needs 15 mA and has a voltage drop of 2 volts. You have a 5 V power source that you would like to power it with. Which resistor value do you need?\n\nTo find the resistor value, we start with finding the voltage drop over the resistor. Since there is a 2 volt drop over the LED, there will be a 3V drop over the resistor.\n\nOk, so we have 3V and we want to have 15 mA going through the resistor and the LED.\n\nTo find the necessary resistor value we use [Ohm’s law](https:\/\/www.build-electronic-circuits.com\/ohms-law\/ \"Ohms law\").\n\n![V = R \\* I \\\\Rightarrow R = \\\\frac{V}{I}](https:\/\/www.build-electronic-circuits.com\/wp-content\/ql-cache\/quicklatex.com-6f2b8dc06d118d5cb21ae673477b706c_l3.png)\n\nthis gives us\n\n![R = \\\\frac{V}{I} = \\\\frac{3V}{15mA} = 200 \\\\Omega](https:\/\/www.build-electronic-circuits.com\/wp-content\/ql-cache\/quicklatex.com-27dd485ce3bc6fa81d8a7f2ca46895e1_l3.png)\n\nSo the necessary value for the current limiting resistor is 200 Ohms.\n\n## Choosing the right resistor\nSo you know that you need a 200 Ohm resistor.\n\nBut when you look for components you find that there are several different [types of resistors](https:\/\/www.build-electronic-circuits.com\/types-of-resistors\/ \"Types of Resistors\").\n\nWell, the only thing you need to be aware of is the wattage rating of the component. How much effect can the resistor handle?\n\nSo you need to figure out how much effect that will be dissipated in your resistor.\n\nTo find this you use the following formula for calculating power\n\n![P = I\\*V](https:\/\/www.build-electronic-circuits.com\/wp-content\/ql-cache\/quicklatex.com-c39c4d5eee8fc625426193aa1bef050c_l3.png)\n\nIt states that power equals the current multiplied with the voltage. So we get\n\n![P = 15 mA \\* 3V = 45mW](https:\/\/www.build-electronic-circuits.com\/wp-content\/ql-cache\/quicklatex.com-19189a0710d554935a9b9a4942cb1aae_l3.png)\n\nThis means your resistor must be able to handle at least 45 mW.\n\nUsually, most resistors handle from 250 mW and up, so it will be easy to find a suitable resistor.\n\n[Return from Current Limiting Resistor to Electronic Schematics](https:\/\/www.build-electronic-circuits.com\/electronic-schematics\/ \"Electronic Schematics – Need-To-Know\")\n\n## More Resistors Tutorials\n- [Introduction to the Resistor](https:\/\/www.build-electronic-circuits.com\/what-is-a-resistor\/)\n- [Types of Resistors](https:\/\/www.build-electronic-circuits.com\/types-of-resistors\/)\n- [Is the current lower after a resistor?](https:\/\/www.build-electronic-circuits.com\/is-the-current-lower-after-a-resistor\/)\n- [The Voltage Divider](https:\/\/www.build-electronic-circuits.com\/voltage-divider\/)\n- [Current Limiting Resistor](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/)\n- [How To Choose A Pull-up Resistor Value](https:\/\/www.build-electronic-circuits.com\/pull-up-resistor-value\/)\n- [The Pull-Up Resistor: How It Works and Choosing a Value](https:\/\/www.build-electronic-circuits.com\/pull-up-resistor\/)\n- [How to Create Your Own Resistor](https:\/\/www.build-electronic-circuits.com\/how-to-create-your-own-resistor\/)\n- [Resistor Color Code Calculator](https:\/\/www.build-electronic-circuits.com\/resistor-color-codes\/)\n\n![ebook cover](https:\/\/www.build-electronic-circuits.com\/wp-content\/uploads\/2024\/04\/Learn-Electronics-Cover-2023-cropped-heavily.png)\n\n## 10 Simple Steps to Learn Electronics\nElectronics is easy when you know what to focus on and what to ignore. Learn what \"the basics\" really is and how to learn it fast.\n\n## 52 thoughts on “Current Limiting Resistor”\n1. Ken Murray\n   \n   [November 13, 2014 at 4:44 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-34072)\n   \n   This is great! Gives the detail we need in easy speak! Thanks\\!\n   \n   [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-34072)\n   - admin\n     \n     [November 13, 2014 at 5:03 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-34079)\n     \n     Great to hear Ken\\!\n     \n     Oyvind\n     \n     [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-34079)\n   - johnb\n     \n     [August 13, 2020 at 7:20 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-112440)\n     \n     yeeeeeeee\n     \n     [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-112440)\n2. Rahul\n   \n   [December 17, 2014 at 5:38 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-42399)\n   \n   Thanks. Simple and great tutorial for a beginner.\n   \n   [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-42399)\n3. faisal\n   \n   [July 1, 2015 at 1:04 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-58591)\n   \n   what a nice post. i love it. thanks\n   \n   [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-58591)\n   - Brendan\n     \n     [January 26, 2019 at 1:08 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-100148)\n     \n     Thanks for the explanation. You kept the explanation nice and simple which is good for the beginners.\n     \n     [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-100148)\n4. Anurag\n   \n   [July 1, 2015 at 7:43 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-58609)\n   \n   Wow simple with a great value…….hats off….\n   \n   [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-58609)\n5. [Naik Javeed](https:\/\/www.build-electronic-circuits.com\/)\n   \n   [September 27, 2015 at 5:04 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-64248)\n   \n   Very Nice! I’m really impressed with these topics!\\!\n   \n   [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-64248)\n6. Prashnt\n   \n   [October 25, 2015 at 3:46 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-65967)\n   \n   very nice answer sir awesome which is really needy for learners.  \n    Sir, now in above you explained the conditions of requirement of resistor in circuit, i am very interested to know what are the conditions that makes to use capacitor & inductor in circuit & how to calculate the exact value of capacitor & inductor.  \n    please explain me the importance of EMI & EMC in the circuit. Please explain sir, waiting for your valuable reply.\n   \n   Regards,  \n    Prashant.\n   \n   [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-65967)\n7. Prashnt\n   \n   [October 25, 2015 at 3:49 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-65968)\n   \n   Hi Sir,\n   \n   Please explain me what is the meaning of Equivalent Series Resistance(ESR) & Its importance in the circuit.\n   \n   Regards,  \n    Prashant.\n   \n   [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-65968)\n8. [Jum](http:\/\/somewhere.com\/)\n   \n   [December 28, 2015 at 4:57 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-69657)\n   \n   Nope. No can do\n   \n   [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-69657)\n9. [Jum](http:\/\/somewhere.com\/)\n   \n   [December 28, 2015 at 4:58 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-69658)\n   \n   It’s not important\n   \n   [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-69658)\n10. Solomon\n    \n    [February 5, 2016 at 2:50 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-70990)\n    \n    What will happen if you use a higher value of resistor ?? .. I used a 9v battery 390ohm resistor to light up an led and it still works for 1k and even 10k .. Pls explain\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-70990)\n    - admin\n      \n      [February 8, 2016 at 3:10 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-71054)\n      \n      If you use a higher value resistor, you get less current through your LED and your LED will be less bright.\n      \n      Cheers\\!  \n       Oyvind\n      \n      [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-71054)\n      - Ranjith\n        \n        [January 8, 2020 at 4:57 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-109022)\n        \n        Sir  \n         In a 5watts Led drive circuit there are 4 tiny flat black resistors marked as R1, R2,R3,and R4′.on top of each resistor,400odds values are marked.  \n         I want to know i f that’s Ohm values or resistance power of each?  \n         2question  \n         Can I remove one of them from the circuit board so as to increase the brightness?  \n         Thanks sir\n        \n        [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-109022)\n11. [Mac Morvant](http:\/\/cox\/)\n    \n    [March 27, 2016 at 5:21 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-72388)\n    \n    It would be nice if Your teaching wouldn’t assume that we dommies new what these formulas were about , As You teach add notations to Your formulas !, to explain them , I no it takes up more space ! Pictures fill in the Q?????\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-72388)\n12. Enoh Chuddy\n    \n    [June 24, 2016 at 5:27 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-74320)\n    \n    I really love this\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-74320)\n13. Radek\n    \n    [September 1, 2016 at 10:59 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-76508)\n    \n    Thank you for this. Now I can order some resistors to test :)\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-76508)\n14. Georgekid\n    \n    [October 13, 2016 at 3:13 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-78281)\n    \n    thank you so much!!!\\!\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-78281)\n15. Mark anthony\n    \n    [December 4, 2016 at 12:09 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-80583)\n    \n    What if a have 12v input and needs to light up a 10v led.what resistor will i need and the type of transisitor to be use?\n    \n    Hoping you could help me.tnx..\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-80583)\n16. Gene Bock\n    \n    [December 27, 2016 at 3:30 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-81769)\n    \n    Explaining scientifc knowledge (or fact) easy is not an easy thing to do. Great explanation and an example. What if I change + and – of the battery? Does an resistor still function what it has to do (does it reduce properly the voltage needed to the LED?)\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-81769)\n    - Gary\n      \n      [May 13, 2017 at 9:11 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-87542)\n      \n      Resistor are not polarity sensitive but LEDs are it will burn out the LED.\n      \n      [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-87542)\n17. Jorge Taylor\n    \n    [April 10, 2017 at 2:43 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-86118)\n    \n    Very easy to understand,thank you.\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-86118)\n18. Sarang Rajendra Thakre\n    \n    [April 13, 2017 at 4:25 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-86284)\n    \n    Nice sir give us information ike this????????????????☺????????☝????\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-86284)\n19. Abdul Rasheed\n    \n    [May 11, 2017 at 4:52 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-87482)\n    \n    Great explanation and very easy to understand as a beginner like me.\n    \n    thanks for your great effort\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-87482)\n20. DE APOGEE\n    \n    [July 24, 2017 at 5:58 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-89623)\n    \n    Great\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-89623)\n21. [robert](http:\/\/les\/)\n    \n    [July 27, 2017 at 3:32 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-89703)\n    \n    i salute you sir thanks this webpage i learn much more\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-89703)\n22. Yuv kishore\n    \n    [November 25, 2017 at 11:07 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-91237)\n    \n    Fantastic!Fantastic!Fantastic\\!\n    \n    I loved the way of explanation…Great work…\n    \n    So easy…\n    \n    Thanks a lot …\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-91237)\n23. rosdy\n    \n    [January 12, 2018 at 10:15 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-91684)\n    \n    very easy to understand even im not very understand english…tq pal…\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-91684)\n24. [Vikranth](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/)\n    \n    [January 23, 2018 at 11:13 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-91746)\n    \n    Beautiful explanation understood in my life…. thanx bro\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-91746)\n25. Brendan\n    \n    [January 26, 2019 at 1:10 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-100149)\n    \n    I liked the explanation as it was kept simple. Good for those beginners like myself\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-100149)\n26. Bala\n    \n    [March 23, 2019 at 3:51 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-101774)\n    \n    Im having a circuit for 12 volt and 240 mA.  \n     Power source: 12 volt 5 amps transformer.\n    \n    What value of resistance should i place?\n    \n    Thanks.\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-101774)\n27. James S Saltaformaggio\n    \n    [May 9, 2019 at 6:05 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-103757)\n    \n    This is exactly what I have been looking for since the age of 6(the first time I shocked myself, plugging in an Oreck vacuum for my grandma). It was then when my life’s mission to learn everything I can about this invisible monster…. Now I can plot my revenge…..⚡💣💥🤳🍻🍾\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-103757)\n28. DNeale\n    \n    [April 8, 2020 at 8:36 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-110077)\n    \n    If we want the current through the entire circuit though shouldn’t we use 5V\/15mA instead of 3V?\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-110077)\n    - admin\n      \n      [April 8, 2020 at 9:50 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-110078)\n      \n      5V is the voltage drop across both the resistor and the LED. But only 3V out of the 5V from the battery drops across the resistor (if we are using a 2V LED). So we need to use 3V.\n      \n      [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-110078)\n29. Prince promise\n    \n    [July 7, 2020 at 1:24 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-111536)\n    \n    Thanks for the post. But i have a question that has been bothering me for long. Why don’t we put the power supply current into consideration?\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-111536)\n    - admin\n      \n      [July 7, 2020 at 4:41 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-111556)\n      \n      That’s because the current specified on the power supply is the maximum current, not the actual current. The actual current flowing is decided by the circuit, not the power supply.\n      \n      [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-111556)\n30. Sungory\n    \n    [August 21, 2020 at 5:11 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-112653)\n    \n    Thanks for the lessons\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-112653)\n31. Sunglory\n    \n    [August 21, 2020 at 5:15 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-112654)\n    \n    More strength to your elbow\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-112654)\n32. Chris Augustine\n    \n    [September 4, 2020 at 4:54 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-113095)\n    \n    So a LED that has a Voltage drop V\\_drop = 1.8V \/ 20mA  \n     is a load on the circuit and thus has a resistance: in this case 90ohm  \n     this is independent of voltage as long as voltage is over 1.8V (right?)\n    \n    Seeing that a resistor is also a load and limits (and conducts) a current; is it even needed if we get the voltage to the LED right at V-drop (perfect world)?\n    \n    But for a given 5V voltage you have a spare 3.2V to get rid of. All voltage must be removed?  \n     So this is your equation to figure out a resistor (in a perfect world): (5.0 – 1.8V) \/ 0.020A  \n     or 160ohm.  \n     Resistors just waste heat so we should minimize their ohms, right? So we should minimize  \n     voltage every chance we have, right?\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-113095)\n    - admin\n      \n      [September 7, 2020 at 4:44 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-113202)\n      \n      Yes to all your questions =)\n      \n      [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-113202)\n33. Levi Haskell\n    \n    [December 13, 2020 at 1:31 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-115790)\n    \n    What if my power source voltage matches the specified LED voltage, let’s say they are both 3V. Do I still need a resistor?\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-115790)\n    - admin\n      \n      [December 14, 2020 at 5:25 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-115840)\n      \n      Then it’s okay to skip the resistor.\n      \n      [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-115840)\n34. Madalin Sava\n    \n    [December 21, 2020 at 12:29 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-116016)\n    \n    Wait, so how did you get to 3V across the resistor? You only measured the current and voltage for the LED. Is there a connection between the 2V in the LED and 3V in the resistor? I don’t get it.\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-116016)\n    - admin\n      \n      [January 4, 2021 at 4:55 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-116357)\n      \n      There is 5V in total. Since 2V drops across the LED, the remaining 3V must drop across the resistor, since there are no more components in series.\n      \n      [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-116357)\n35. David\n    \n    [December 23, 2020 at 10:17 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-116083)\n    \n    Hi. Love the site. I suggest being more fastidious with your units. Make a note when using milliamps or milliwatts, because the formulas are in amps and watts. Conversions are easy, as you know, but people can get tripped up with that.\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-116083)\n    - admin\n      \n      [January 4, 2021 at 4:55 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-116358)\n      \n      Thanks, I’ll try to remember that\\!\n      \n      [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-116358)\n36. Pambos\n    \n    [January 26, 2021 at 1:54 pm](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-116937)\n    \n    Great, thank you , cool\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-116937)\n37. Mani\n    \n    [August 13, 2021 at 4:24 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-122645)\n    \n    If we used 100 ohm resistor instead of 160 ohm , will current increase in this circuit or with same current only voltage increase across led?  \n     If current is same as 20 ma 2 v will be dropped across resistor and led will get 3 v or  \n     If voltage drop same 3v\/100 ohms .03 amp or 30 ma will flow through the circuit  \n     Actually what will happen please explain….\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-122645)\n    - admin\n      \n      [August 13, 2021 at 8:40 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-122650)\n      \n      If you increase the resistance from 100 to 160 ohm (and the voltage stays the same), the current will decrease.\n      \n      [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-122650)\n38. John Smith\n    \n    [February 12, 2022 at 7:42 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-125347)\n    \n    First time I understand how I can calculate LED resistor\n    \n    . THANK YOU VERY MUCH\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-125347)\n39. Fran\n    \n    [October 18, 2022 at 2:18 am](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-127153)\n    \n    Thank you very much, simple, short and trully informative, it really helped.\n    \n    [Reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#comment-127153)\n### Leave a Comment [Cancel reply](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/#respond)\n\n## More Resistors Tutorials\n- [Introduction to the Resistor](https:\/\/www.build-electronic-circuits.com\/what-is-a-resistor\/)\n- [Types of Resistors](https:\/\/www.build-electronic-circuits.com\/types-of-resistors\/)\n- [Is the current lower after a resistor?](https:\/\/www.build-electronic-circuits.com\/is-the-current-lower-after-a-resistor\/)\n- [The Voltage Divider](https:\/\/www.build-electronic-circuits.com\/voltage-divider\/)\n- [Current Limiting Resistor](https:\/\/www.build-electronic-circuits.com\/current-limiting-resistor\/)\n- [How To Choose A Pull-up Resistor Value](https:\/\/www.build-electronic-circuits.com\/pull-up-resistor-value\/)\n- [The Pull-Up Resistor: How It Works and Choosing a Value](https:\/\/www.build-electronic-circuits.com\/pull-up-resistor\/)\n- [How to Create Your Own Resistor](https:\/\/www.build-electronic-circuits.com\/how-to-create-your-own-resistor\/)\n- [Resistor Color Code Calculator](https:\/\/www.build-electronic-circuits.com\/resistor-color-codes\/)\n\n![](https:\/\/www.build-electronic-circuits.com\/wp-content\/uploads\/2023\/09\/Logo-WP-ratio.png)\n\n## Other Topics\n- [Circuit Calculators & Converters](https:\/\/www.build-electronic-circuits.com\/circuit-calculator-conversion\/)\n- [Maker Lifestyle](https:\/\/www.build-electronic-circuits.com\/category\/maker-lifestyle\/)\n- [Newsletter Archive](https:\/\/www.build-electronic-circuits.com\/category\/mail-archive\/)\n- [Podcast](https:\/\/www.build-electronic-circuits.com\/category\/maker-lifestyle\/podcast\/)\n- [Blog](https:\/\/www.build-electronic-circuits.com\/blog\/)\n\n## Social:\n- [Facebook](https:\/\/www.facebook.com\/BuildElectronicCircuits\/)\n- [Twitter](https:\/\/twitter.com\/oyvdahl)\n- [YouTube](https:\/\/youtube.com\/c\/Build-electronic-circuits)\n\n## Products\n- [Electronics Course](https:\/\/ohmify.com\/)\n- [Other Products](https:\/\/www.build-electronic-circuits.com\/products\/)\n\nAll contents are Copyright © 2026 by Ohmify AS\n\n×\n\n![ebook cover](https:\/\/www.build-electronic-circuits.com\/wp-content\/uploads\/2024\/04\/Learn-Electronics-Cover-2023-cropped-heavily.png)\n\n## 10 Simple Steps to Learn Electronics\nElectronics is easy when you know what to focus on and what to ignore. Learn what \"the basics\" really is and how to learn it fast.","attrs_readable_markdown":"A current limiting resistor is a resistor that is used to reduce the current in a circuit.\n\nA simple example is a resistor in series with an LED.\n\n![fi-simplest-circuits](https:\/\/www.build-electronic-circuits.com\/wp-content\/uploads\/2013\/09\/fi-simplest-circuits.jpg)\n\nYou would usually want to have a current limiting resistor in series with your LED so that you can control the amount of current through the LED.\n\nIf too much current is going through your LED, it will burn out too fast. If too little current is going through it, it might not be enough to lit the LED.\n\n## Calculating the necessary resistor value\n![A current limiting resistor in series with an LED](https:\/\/www.build-electronic-circuits.com\/wp-content\/uploads\/2013\/09\/current-limiting-resistor-with-led.png)\n\nCheck the datasheet of your component to find voltage drop and the appropriate current for your LED.\n\nIf you can’t find a datasheet, you can test it.\n\nConnect the LED and a resistor in series to a variable voltage source. Start at 0 volts and increase the voltage gradually until the LED lit up.\n\nMeasure the voltage over the LED and the current going through.\n\n![ebook cover](https:\/\/www.build-electronic-circuits.com\/wp-content\/uploads\/2024\/04\/Learn-Electronics-Cover-2023-cropped-heavily.png)\n\n## 10 Simple Steps to Learn Electronics\nElectronics is easy when you know what to focus on and what to ignore. Learn what \"the basics\" really is and how to learn it fast.\n\nLet’s say the LED needs 15 mA and has a voltage drop of 2 volts. You have a 5 V power source that you would like to power it with. Which resistor value do you need?\n\nTo find the resistor value, we start with finding the voltage drop over the resistor. Since there is a 2 volt drop over the LED, there will be a 3V drop over the resistor.\n\nOk, so we have 3V and we want to have 15 mA going through the resistor and the LED.\n\nTo find the necessary resistor value we use [Ohm’s law](https:\/\/www.build-electronic-circuits.com\/ohms-law\/ \"Ohms law\").\n\n![V = R \\* I \\\\Rightarrow R = \\\\frac{V}{I}](https:\/\/www.build-electronic-circuits.com\/wp-content\/ql-cache\/quicklatex.com-6f2b8dc06d118d5cb21ae673477b706c_l3.png)\n\nthis gives us\n\n![R = \\\\frac{V}{I} = \\\\frac{3V}{15mA} = 200 \\\\Omega](https:\/\/www.build-electronic-circuits.com\/wp-content\/ql-cache\/quicklatex.com-27dd485ce3bc6fa81d8a7f2ca46895e1_l3.png)\n\nSo the necessary value for the current limiting resistor is 200 Ohms.\n\n## Choosing the right resistor\nSo you know that you need a 200 Ohm resistor.\n\nBut when you look for components you find that there are several different [types of resistors](https:\/\/www.build-electronic-circuits.com\/types-of-resistors\/ \"Types of Resistors\").\n\nWell, the only thing you need to be aware of is the wattage rating of the component. How much effect can the resistor handle?\n\nSo you need to figure out how much effect that will be dissipated in your resistor.\n\nTo find this you use the following formula for calculating power\n\n![P = I\\*V](https:\/\/www.build-electronic-circuits.com\/wp-content\/ql-cache\/quicklatex.com-c39c4d5eee8fc625426193aa1bef050c_l3.png)\n\nIt states that power equals the current multiplied with the voltage. So we get\n\n![P = 15 mA \\* 3V = 45mW](https:\/\/www.build-electronic-circuits.com\/wp-content\/ql-cache\/quicklatex.com-19189a0710d554935a9b9a4942cb1aae_l3.png)\n\nThis means your resistor must be able to handle at least 45 mW.\n\nUsually, most resistors handle from 250 mW and up, so it will be easy to find a suitable resistor.\n\n[Return from Current Limiting Resistor to Electronic Schematics](https:\/\/www.build-electronic-circuits.com\/electronic-schematics\/ \"Electronic Schematics – Need-To-Know\")\n\n## More Resistors Tutorials\n![ebook cover](https:\/\/www.build-electronic-circuits.com\/wp-content\/uploads\/2024\/04\/Learn-Electronics-Cover-2023-cropped-heavily.png)\n\n## 10 Simple Steps to Learn Electronics\nElectronics is easy when you know what to focus on and what to ignore. Learn what \"the basics\" really is and how to learn it fast.","meta_canonical":null}

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Meta Title	Current Limiting Resistor
Meta Description	A current limiting resistor is often used to control the current going through an LED. Learn how to select the right resistor value and type.
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Boilerpipe Text	A current limiting resistor is a resistor that is used to reduce the current in a circuit. A simple example is a resistor in series with an LED. You would usually want to have a current limiting resistor in series with your LED so that you can control the amount of current through the LED. If too much current is going through your LED, it will burn out too fast. If too little current is going through it, it might not be enough to lit the LED. Calculating the necessary resistor value Check the datasheet of your component to find voltage drop and the appropriate current for your LED. If you can’t find a datasheet, you can test it. Connect the LED and a resistor in series to a variable voltage source. Start at 0 volts and increase the voltage gradually until the LED lit up. Measure the voltage over the LED and the current going through. 10 Simple Steps to Learn Electronics Electronics is easy when you know what to focus on and what to ignore. Learn what "the basics" really is and how to learn it fast. Let’s say the LED needs 15 mA and has a voltage drop of 2 volts. You have a 5 V power source that you would like to power it with. Which resistor value do you need? To find the resistor value, we start with finding the voltage drop over the resistor. Since there is a 2 volt drop over the LED, there will be a 3V drop over the resistor. Ok, so we have 3V and we want to have 15 mA going through the resistor and the LED. To find the necessary resistor value we use Ohm’s law . this gives us So the necessary value for the current limiting resistor is 200 Ohms. Choosing the right resistor So you know that you need a 200 Ohm resistor. But when you look for components you find that there are several different types of resistors . Well, the only thing you need to be aware of is the wattage rating of the component. How much effect can the resistor handle? So you need to figure out how much effect that will be dissipated in your resistor. To find this you use the following formula for calculating power It states that power equals the current multiplied with the voltage. So we get This means your resistor must be able to handle at least 45 mW. Usually, most resistors handle from 250 mW and up, so it will be easy to find a suitable resistor. Return from Current Limiting Resistor to Electronic Schematics More Resistors Tutorials 10 Simple Steps to Learn Electronics Electronics is easy when you know what to focus on and what to ignore. Learn what "the basics" really is and how to learn it fast.
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A simple example is a resistor in series with an LED. ![fi-simplest-circuits](https://www.build-electronic-circuits.com/wp-content/uploads/2013/09/fi-simplest-circuits.jpg) You would usually want to have a current limiting resistor in series with your LED so that you can control the amount of current through the LED. If too much current is going through your LED, it will burn out too fast. If too little current is going through it, it might not be enough to lit the LED. ## Calculating the necessary resistor value ![A current limiting resistor in series with an LED](https://www.build-electronic-circuits.com/wp-content/uploads/2013/09/current-limiting-resistor-with-led.png) Check the datasheet of your component to find voltage drop and the appropriate current for your LED. If you can’t find a datasheet, you can test it. Connect the LED and a resistor in series to a variable voltage source. Start at 0 volts and increase the voltage gradually until the LED lit up. Measure the voltage over the LED and the current going through. ![ebook cover](https://www.build-electronic-circuits.com/wp-content/uploads/2024/04/Learn-Electronics-Cover-2023-cropped-heavily.png) ## 10 Simple Steps to Learn Electronics Electronics is easy when you know what to focus on and what to ignore. Learn what "the basics" really is and how to learn it fast. Let’s say the LED needs 15 mA and has a voltage drop of 2 volts. You have a 5 V power source that you would like to power it with. Which resistor value do you need? To find the resistor value, we start with finding the voltage drop over the resistor. Since there is a 2 volt drop over the LED, there will be a 3V drop over the resistor. Ok, so we have 3V and we want to have 15 mA going through the resistor and the LED. To find the necessary resistor value we use [Ohm’s law](https://www.build-electronic-circuits.com/ohms-law/ "Ohms law"). ![V = R \* I \\Rightarrow R = \\frac{V}{I}](https://www.build-electronic-circuits.com/wp-content/ql-cache/quicklatex.com-6f2b8dc06d118d5cb21ae673477b706c_l3.png) this gives us ![R = \\frac{V}{I} = \\frac{3V}{15mA} = 200 \\Omega](https://www.build-electronic-circuits.com/wp-content/ql-cache/quicklatex.com-27dd485ce3bc6fa81d8a7f2ca46895e1_l3.png) So the necessary value for the current limiting resistor is 200 Ohms. ## Choosing the right resistor So you know that you need a 200 Ohm resistor. But when you look for components you find that there are several different [types of resistors](https://www.build-electronic-circuits.com/types-of-resistors/ "Types of Resistors"). Well, the only thing you need to be aware of is the wattage rating of the component. How much effect can the resistor handle? So you need to figure out how much effect that will be dissipated in your resistor. To find this you use the following formula for calculating power ![P = I\V](https://www.build-electronic-circuits.com/wp-content/ql-cache/quicklatex.com-c39c4d5eee8fc625426193aa1bef050c_l3.png) It states that power equals the current multiplied with the voltage. So we get ![P = 15 mA \ 3V = 45mW](https://www.build-electronic-circuits.com/wp-content/ql-cache/quicklatex.com-19189a0710d554935a9b9a4942cb1aae_l3.png) This means your resistor must be able to handle at least 45 mW. Usually, most resistors handle from 250 mW and up, so it will be easy to find a suitable resistor. [Return from Current Limiting Resistor to Electronic Schematics](https://www.build-electronic-circuits.com/electronic-schematics/ "Electronic Schematics – Need-To-Know") ## More Resistors Tutorials - [Introduction to the Resistor](https://www.build-electronic-circuits.com/what-is-a-resistor/) - [Types of Resistors](https://www.build-electronic-circuits.com/types-of-resistors/) - [Is the current lower after a resistor?](https://www.build-electronic-circuits.com/is-the-current-lower-after-a-resistor/) - [The Voltage Divider](https://www.build-electronic-circuits.com/voltage-divider/) - [Current Limiting Resistor](https://www.build-electronic-circuits.com/current-limiting-resistor/) - [How To Choose A Pull-up Resistor Value](https://www.build-electronic-circuits.com/pull-up-resistor-value/) - [The Pull-Up Resistor: How It Works and Choosing a Value](https://www.build-electronic-circuits.com/pull-up-resistor/) - [How to Create Your Own Resistor](https://www.build-electronic-circuits.com/how-to-create-your-own-resistor/) - [Resistor Color Code Calculator](https://www.build-electronic-circuits.com/resistor-color-codes/) ![ebook cover](https://www.build-electronic-circuits.com/wp-content/uploads/2024/04/Learn-Electronics-Cover-2023-cropped-heavily.png) ## 10 Simple Steps to Learn Electronics Electronics is easy when you know what to focus on and what to ignore. Learn what "the basics" really is and how to learn it fast. ## 52 thoughts on “Current Limiting Resistor” 1. Ken Murray [November 13, 2014 at 4:44 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-34072) This is great! Gives the detail we need in easy speak! Thanks\! [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-34072) - admin [November 13, 2014 at 5:03 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-34079) Great to hear Ken\! Oyvind [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-34079) - johnb [August 13, 2020 at 7:20 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-112440) yeeeeeeee [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-112440) 2. Rahul [December 17, 2014 at 5:38 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-42399) Thanks. Simple and great tutorial for a beginner. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-42399) 3. faisal [July 1, 2015 at 1:04 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-58591) what a nice post. i love it. thanks [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-58591) - Brendan [January 26, 2019 at 1:08 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-100148) Thanks for the explanation. You kept the explanation nice and simple which is good for the beginners. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-100148) 4. Anurag [July 1, 2015 at 7:43 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-58609) Wow simple with a great value…….hats off…. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-58609) 5. [Naik Javeed](https://www.build-electronic-circuits.com/) [September 27, 2015 at 5:04 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-64248) Very Nice! I’m really impressed with these topics!\! [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-64248) 6. Prashnt [October 25, 2015 at 3:46 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-65967) very nice answer sir awesome which is really needy for learners. Sir, now in above you explained the conditions of requirement of resistor in circuit, i am very interested to know what are the conditions that makes to use capacitor & inductor in circuit & how to calculate the exact value of capacitor & inductor. please explain me the importance of EMI & EMC in the circuit. Please explain sir, waiting for your valuable reply. Regards, Prashant. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-65967) 7. Prashnt [October 25, 2015 at 3:49 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-65968) Hi Sir, Please explain me what is the meaning of Equivalent Series Resistance(ESR) & Its importance in the circuit. Regards, Prashant. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-65968) 8. [Jum](http://somewhere.com/) [December 28, 2015 at 4:57 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-69657) Nope. No can do [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-69657) 9. [Jum](http://somewhere.com/) [December 28, 2015 at 4:58 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-69658) It’s not important [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-69658) 10. Solomon [February 5, 2016 at 2:50 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-70990) What will happen if you use a higher value of resistor ?? .. I used a 9v battery 390ohm resistor to light up an led and it still works for 1k and even 10k .. Pls explain [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-70990) - admin [February 8, 2016 at 3:10 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-71054) If you use a higher value resistor, you get less current through your LED and your LED will be less bright. Cheers\! Oyvind [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-71054) - Ranjith [January 8, 2020 at 4:57 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-109022) Sir In a 5watts Led drive circuit there are 4 tiny flat black resistors marked as R1, R2,R3,and R4′.on top of each resistor,400odds values are marked. I want to know i f that’s Ohm values or resistance power of each? 2question Can I remove one of them from the circuit board so as to increase the brightness? Thanks sir [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-109022) 11. [Mac Morvant](http://cox/) [March 27, 2016 at 5:21 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-72388) It would be nice if Your teaching wouldn’t assume that we dommies new what these formulas were about , As You teach add notations to Your formulas !, to explain them , I no it takes up more space ! Pictures fill in the Q????? [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-72388) 12. Enoh Chuddy [June 24, 2016 at 5:27 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-74320) I really love this [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-74320) 13. Radek [September 1, 2016 at 10:59 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-76508) Thank you for this. Now I can order some resistors to test :) [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-76508) 14. Georgekid [October 13, 2016 at 3:13 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-78281) thank you so much!!!\! [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-78281) 15. Mark anthony [December 4, 2016 at 12:09 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-80583) What if a have 12v input and needs to light up a 10v led.what resistor will i need and the type of transisitor to be use? Hoping you could help me.tnx.. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-80583) 16. Gene Bock [December 27, 2016 at 3:30 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-81769) Explaining scientifc knowledge (or fact) easy is not an easy thing to do. Great explanation and an example. What if I change + and – of the battery? Does an resistor still function what it has to do (does it reduce properly the voltage needed to the LED?) [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-81769) - Gary [May 13, 2017 at 9:11 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-87542) Resistor are not polarity sensitive but LEDs are it will burn out the LED. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-87542) 17. Jorge Taylor [April 10, 2017 at 2:43 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-86118) Very easy to understand,thank you. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-86118) 18. Sarang Rajendra Thakre [April 13, 2017 at 4:25 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-86284) Nice sir give us information ike this????????????????☺????????☝???? [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-86284) 19. Abdul Rasheed [May 11, 2017 at 4:52 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-87482) Great explanation and very easy to understand as a beginner like me. thanks for your great effort [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-87482) 20. DE APOGEE [July 24, 2017 at 5:58 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-89623) Great [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-89623) 21. [robert](http://les/) [July 27, 2017 at 3:32 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-89703) i salute you sir thanks this webpage i learn much more [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-89703) 22. Yuv kishore [November 25, 2017 at 11:07 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-91237) Fantastic!Fantastic!Fantastic\! I loved the way of explanation…Great work… So easy… Thanks a lot … [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-91237) 23. rosdy [January 12, 2018 at 10:15 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-91684) very easy to understand even im not very understand english…tq pal… [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-91684) 24. [Vikranth](https://www.build-electronic-circuits.com/current-limiting-resistor/) [January 23, 2018 at 11:13 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-91746) Beautiful explanation understood in my life…. thanx bro [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-91746) 25. Brendan [January 26, 2019 at 1:10 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-100149) I liked the explanation as it was kept simple. Good for those beginners like myself [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-100149) 26. Bala [March 23, 2019 at 3:51 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-101774) Im having a circuit for 12 volt and 240 mA. Power source: 12 volt 5 amps transformer. What value of resistance should i place? Thanks. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-101774) 27. James S Saltaformaggio [May 9, 2019 at 6:05 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-103757) This is exactly what I have been looking for since the age of 6(the first time I shocked myself, plugging in an Oreck vacuum for my grandma). It was then when my life’s mission to learn everything I can about this invisible monster…. Now I can plot my revenge…..⚡💣💥🤳🍻🍾 [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-103757) 28. DNeale [April 8, 2020 at 8:36 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-110077) If we want the current through the entire circuit though shouldn’t we use 5V/15mA instead of 3V? [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-110077) - admin [April 8, 2020 at 9:50 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-110078) 5V is the voltage drop across both the resistor and the LED. But only 3V out of the 5V from the battery drops across the resistor (if we are using a 2V LED). So we need to use 3V. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-110078) 29. Prince promise [July 7, 2020 at 1:24 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-111536) Thanks for the post. But i have a question that has been bothering me for long. Why don’t we put the power supply current into consideration? [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-111536) - admin [July 7, 2020 at 4:41 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-111556) That’s because the current specified on the power supply is the maximum current, not the actual current. The actual current flowing is decided by the circuit, not the power supply. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-111556) 30. Sungory [August 21, 2020 at 5:11 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-112653) Thanks for the lessons [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-112653) 31. Sunglory [August 21, 2020 at 5:15 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-112654) More strength to your elbow [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-112654) 32. Chris Augustine [September 4, 2020 at 4:54 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-113095) So a LED that has a Voltage drop V\_drop = 1.8V / 20mA is a load on the circuit and thus has a resistance: in this case 90ohm this is independent of voltage as long as voltage is over 1.8V (right?) Seeing that a resistor is also a load and limits (and conducts) a current; is it even needed if we get the voltage to the LED right at V-drop (perfect world)? But for a given 5V voltage you have a spare 3.2V to get rid of. All voltage must be removed? So this is your equation to figure out a resistor (in a perfect world): (5.0 – 1.8V) / 0.020A or 160ohm. Resistors just waste heat so we should minimize their ohms, right? So we should minimize voltage every chance we have, right? [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-113095) - admin [September 7, 2020 at 4:44 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-113202) Yes to all your questions =) [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-113202) 33. Levi Haskell [December 13, 2020 at 1:31 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-115790) What if my power source voltage matches the specified LED voltage, let’s say they are both 3V. Do I still need a resistor? [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-115790) - admin [December 14, 2020 at 5:25 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-115840) Then it’s okay to skip the resistor. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-115840) 34. Madalin Sava [December 21, 2020 at 12:29 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-116016) Wait, so how did you get to 3V across the resistor? You only measured the current and voltage for the LED. Is there a connection between the 2V in the LED and 3V in the resistor? I don’t get it. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-116016) - admin [January 4, 2021 at 4:55 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-116357) There is 5V in total. Since 2V drops across the LED, the remaining 3V must drop across the resistor, since there are no more components in series. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-116357) 35. David [December 23, 2020 at 10:17 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-116083) Hi. Love the site. I suggest being more fastidious with your units. Make a note when using milliamps or milliwatts, because the formulas are in amps and watts. Conversions are easy, as you know, but people can get tripped up with that. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-116083) - admin [January 4, 2021 at 4:55 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-116358) Thanks, I’ll try to remember that\! [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-116358) 36. Pambos [January 26, 2021 at 1:54 pm](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-116937) Great, thank you , cool [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-116937) 37. Mani [August 13, 2021 at 4:24 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-122645) If we used 100 ohm resistor instead of 160 ohm , will current increase in this circuit or with same current only voltage increase across led? If current is same as 20 ma 2 v will be dropped across resistor and led will get 3 v or If voltage drop same 3v/100 ohms .03 amp or 30 ma will flow through the circuit Actually what will happen please explain…. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-122645) - admin [August 13, 2021 at 8:40 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-122650) If you increase the resistance from 100 to 160 ohm (and the voltage stays the same), the current will decrease. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-122650) 38. John Smith [February 12, 2022 at 7:42 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-125347) First time I understand how I can calculate LED resistor . THANK YOU VERY MUCH [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-125347) 39. Fran [October 18, 2022 at 2:18 am](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-127153) Thank you very much, simple, short and trully informative, it really helped. [Reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#comment-127153) ### Leave a Comment [Cancel reply](https://www.build-electronic-circuits.com/current-limiting-resistor/#respond) ## More Resistors Tutorials - [Introduction to the Resistor](https://www.build-electronic-circuits.com/what-is-a-resistor/) - [Types of Resistors](https://www.build-electronic-circuits.com/types-of-resistors/) - [Is the current lower after a resistor?](https://www.build-electronic-circuits.com/is-the-current-lower-after-a-resistor/) - [The Voltage Divider](https://www.build-electronic-circuits.com/voltage-divider/) - [Current Limiting Resistor](https://www.build-electronic-circuits.com/current-limiting-resistor/) - [How To Choose A Pull-up Resistor Value](https://www.build-electronic-circuits.com/pull-up-resistor-value/) - [The Pull-Up Resistor: How It Works and Choosing a Value](https://www.build-electronic-circuits.com/pull-up-resistor/) - [How to Create Your Own Resistor](https://www.build-electronic-circuits.com/how-to-create-your-own-resistor/) - [Resistor Color Code Calculator](https://www.build-electronic-circuits.com/resistor-color-codes/) ![](https://www.build-electronic-circuits.com/wp-content/uploads/2023/09/Logo-WP-ratio.png) ## Other Topics - [Circuit Calculators & Converters](https://www.build-electronic-circuits.com/circuit-calculator-conversion/) - [Maker Lifestyle](https://www.build-electronic-circuits.com/category/maker-lifestyle/) - [Newsletter Archive](https://www.build-electronic-circuits.com/category/mail-archive/) - [Podcast](https://www.build-electronic-circuits.com/category/maker-lifestyle/podcast/) - [Blog](https://www.build-electronic-circuits.com/blog/) ## Social: - [Facebook](https://www.facebook.com/BuildElectronicCircuits/) - [Twitter](https://twitter.com/oyvdahl) - [YouTube](https://youtube.com/c/Build-electronic-circuits) ## Products - [Electronics Course](https://ohmify.com/) - [Other Products](https://www.build-electronic-circuits.com/products/) All contents are Copyright © 2026 by Ohmify AS × ![ebook cover](https://www.build-electronic-circuits.com/wp-content/uploads/2024/04/Learn-Electronics-Cover-2023-cropped-heavily.png) ## 10 Simple Steps to Learn Electronics Electronics is easy when you know what to focus on and what to ignore. 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Readable Markdown	A current limiting resistor is a resistor that is used to reduce the current in a circuit. A simple example is a resistor in series with an LED. ![fi-simplest-circuits](https://www.build-electronic-circuits.com/wp-content/uploads/2013/09/fi-simplest-circuits.jpg) You would usually want to have a current limiting resistor in series with your LED so that you can control the amount of current through the LED. If too much current is going through your LED, it will burn out too fast. If too little current is going through it, it might not be enough to lit the LED. ## Calculating the necessary resistor value ![A current limiting resistor in series with an LED](https://www.build-electronic-circuits.com/wp-content/uploads/2013/09/current-limiting-resistor-with-led.png) Check the datasheet of your component to find voltage drop and the appropriate current for your LED. If you can’t find a datasheet, you can test it. Connect the LED and a resistor in series to a variable voltage source. Start at 0 volts and increase the voltage gradually until the LED lit up. Measure the voltage over the LED and the current going through. ![ebook cover](https://www.build-electronic-circuits.com/wp-content/uploads/2024/04/Learn-Electronics-Cover-2023-cropped-heavily.png) ## 10 Simple Steps to Learn Electronics Electronics is easy when you know what to focus on and what to ignore. Learn what "the basics" really is and how to learn it fast. Let’s say the LED needs 15 mA and has a voltage drop of 2 volts. You have a 5 V power source that you would like to power it with. Which resistor value do you need? To find the resistor value, we start with finding the voltage drop over the resistor. Since there is a 2 volt drop over the LED, there will be a 3V drop over the resistor. Ok, so we have 3V and we want to have 15 mA going through the resistor and the LED. To find the necessary resistor value we use [Ohm’s law](https://www.build-electronic-circuits.com/ohms-law/ "Ohms law"). ![V = R \* I \\Rightarrow R = \\frac{V}{I}](https://www.build-electronic-circuits.com/wp-content/ql-cache/quicklatex.com-6f2b8dc06d118d5cb21ae673477b706c_l3.png) this gives us ![R = \\frac{V}{I} = \\frac{3V}{15mA} = 200 \\Omega](https://www.build-electronic-circuits.com/wp-content/ql-cache/quicklatex.com-27dd485ce3bc6fa81d8a7f2ca46895e1_l3.png) So the necessary value for the current limiting resistor is 200 Ohms. ## Choosing the right resistor So you know that you need a 200 Ohm resistor. But when you look for components you find that there are several different [types of resistors](https://www.build-electronic-circuits.com/types-of-resistors/ "Types of Resistors"). Well, the only thing you need to be aware of is the wattage rating of the component. How much effect can the resistor handle? So you need to figure out how much effect that will be dissipated in your resistor. To find this you use the following formula for calculating power ![P = I\V](https://www.build-electronic-circuits.com/wp-content/ql-cache/quicklatex.com-c39c4d5eee8fc625426193aa1bef050c_l3.png) It states that power equals the current multiplied with the voltage. So we get ![P = 15 mA \ 3V = 45mW](https://www.build-electronic-circuits.com/wp-content/ql-cache/quicklatex.com-19189a0710d554935a9b9a4942cb1aae_l3.png) This means your resistor must be able to handle at least 45 mW. Usually, most resistors handle from 250 mW and up, so it will be easy to find a suitable resistor. [Return from Current Limiting Resistor to Electronic Schematics](https://www.build-electronic-circuits.com/electronic-schematics/ "Electronic Schematics – Need-To-Know") ## More Resistors Tutorials ![ebook cover](https://www.build-electronic-circuits.com/wp-content/uploads/2024/04/Learn-Electronics-Cover-2023-cropped-heavily.png) ## 10 Simple Steps to Learn Electronics Electronics is easy when you know what to focus on and what to ignore. Learn what "the basics" really is and how to learn it fast.
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