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arduino help 5 volt and 13 volt leds

Barry B.
user 7406427
Santa Ana, CA
Post #: 61
Hello, I'm working on a project that will have about 70 individually controlled LEDs. I've been using a shield that controls 32 pwms, and you can stack the shields for more and more pwms. So far so good, but their output is 5v. This works great for 5v leds, but I do need about 10 13v leds as flashers too. Do you guys know how I can control that? Maybe build some kinda gate that accepts the 5v signal, which switches to turn on and off a 13v signal? Maybe I'm making this too complicated. I should preface this by saying, I'm an artist, I'm just starting to get into Arduino.

I'd love to hear your ideas.
Jim
user 80978712
Long Beach, CA
Post #: 5
A common NPN darlington transistor like an 2N2222, or a Darlington array like the common ULN2003 would likely work for your application. The choice depends on the simultaneous current requirement for the 13V parts.

To put it as simply as possible, one Arduino pin controls one transistor. The 13V supply connects to the 'high side' (anode) of the LED. The 'collector' pin of the transistor connects to the cathode. When the Arduino pin supplies a positive voltage 3.3-5V to the 'base' pin of the transistor, the transistor turns on and completes the circuit, and 'switches the low side' (cathode) to ground.

If the 13 volt parts require a limiting resistor, put it in the circuit on either side of the LED. Google will return a thousand examples of switching 12 volts, or a relay, with an Arduino, so there will be plenty to read and look at. The above should get you going.
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