# Regarding Raphael kit 1.1.1 LED blinking. Why is it 220 ohm?

**URL:** <https://forum.sunfounder.com/t/regarding-raphael-kit-1-1-1-led-blinking-why-is-it-220-ohm/1328>\
**Category:** Learning kit for Raspberry Pi\
**Created:** [July 7, 2024, 4:47am UTC](https://forum.sunfounder.com/t/regarding-raphael-kit-1-1-1-led-blinking-why-is-it-220-ohm/1328 "2024-07-07T04:47:44Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Miyabee-craft](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Miyabee-craft](https://forum.sunfounder.com/u/Miyabee-craft)\
**Post date:** [July 7, 2024, 4:47am UTC](https://forum.sunfounder.com/t/regarding-raphael-kit-1-1-1-led-blinking-why-is-it-220-ohm/1328/1 "2024-07-07T04:47:44Z")

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Hi !  
Regarding Raphael kit 1.1.1 LED blinking, the resistance value used in the circuit is 220Ω. Why is it 220Ω?  
The following page says that the LED is 1.8V, the current is a maximum of 20mA, and the resistance value can be calculated as R = (Vsupply – VD)/I. The GPIO 3.3V terminal is used. From this, the resistance value is calculated as R=(3.3-1.8)/0.02=75Ω, and even if the current is 10mA, R=150Ω. Why was 220Ω chosen?  
[https://docs.sunfounder.com/projects/raphael-kit/en/latest/component/component\_led.html#cpn-led](https://docs.sunfounder.com/projects/raphael-kit/en/latest/component/component_led.html#cpn-led)

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**Author:** ![SunFounder\_Moderator](https://avatars.discourse-cdn.com/v4/letter/s/34f0e0/32.png) [@SunFounder\_Moderator](https://forum.sunfounder.com/u/SunFounder_Moderator)\
**Post date:** [July 8, 2024, 8:58am UTC](https://forum.sunfounder.com/t/regarding-raphael-kit-1-1-1-led-blinking-why-is-it-220-ohm/1328/2 "2024-07-08T08:58:04Z")

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Yes, your calculations are correct. However, we don’t necessarily need to set the LED to such a high brightness level. It’s more common to use a standard resistor, such as a 220R or 330R resistor.

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**Author:** ![Miyabee-craft](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Miyabee-craft](https://forum.sunfounder.com/u/Miyabee-craft)\
**Post date:** [July 14, 2024, 3:59pm UTC](https://forum.sunfounder.com/t/regarding-raphael-kit-1-1-1-led-blinking-why-is-it-220-ohm/1328/3 "2024-07-14T15:59:28Z")

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Sorry for the late reply.Thank you for your answer.The calculation was correct, but in reality, standard resistance values are used. I understand now.

2024年7月8日(月) 18:08 SunFounder\_Moderator via Sunfounder Forum \<[notifications@sunfounder.discoursemail.com](mailto:notifications@sunfounder.discoursemail.com)\>: