Hello,
I am trying to figure out how to calculate the resistor value for the SMD LEDs. There are 3 groups of LEDs I want to control with 3 of the pins on the Trinket (5V).
The LED specs from the seller:
1206 SMD SMT LED
Max. Reverse Current: 10uA
Max. Forward Current: 20Ma
Max. Reverse Voltage: 5V
Forward Voltage: 3.0-3.2V
This is the breadboard.
Can somebody help?
If I calculated this correctly, I think I need 100 ohms for each LED.
Thanks.
How to calculate resistor values for this project?
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Please be positive and constructive with your questions and comments.
- ericbrian
- Posts: 26
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- adafruit_support_bill
- Posts: 88086
- Joined: Sat Feb 07, 2009 10:11 am
Re: How to calculate resistor values for this project?
Yes. 100 ohms would give you 20mA through the led.
- phild13
- Posts: 247
- Joined: Mon Sep 10, 2012 1:05 pm
Re: How to calculate resistor values for this project?
I think the max a Trinket pin can supply is 20mA into a load. As drawn, each LED would draw 20mA and so you would have 100mA on each trinket pin which will damage the trinket or cause it to not work. You will need a separate supply and drive each set of 4 leds by using a transistor capable of supporting the 100mA load. Turn the transistor on/off with the Trinket pins.
Please be positive and constructive with your questions and comments.