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Help powering LEDs via external 5V source, instead of Arduin
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Help powering LEDs via external 5V source, instead of Arduin

by atomickid on Sun Aug 04, 2019 5:01 pm

My test project consisted of only a couple of LEDs, wired to an Uno, and triggered on via a capacitive touch switch. At scale I expect to have close to 50 of these LEDs, and realize I need to re-engineer this test setup to take power from an external 5V supply, and not from the Arduino in order to migrate this to the larger setup.

Unfortunately I'm a bit stumped. The circuit right now uses Arduino GND and receives the 5V+ from PWM~9 (when the switch detects a touch event).

Where I mess up the circuit is if I move my +5V from PWM 9 and connect to the power supplies +5V then does my LED's ground side go into the PWM? I'm suspecting "no", because from what I've learned so far ground is typically shared across all the components, and we don't want to connect that to a PWM.

So, if this is the case, I would now have LED's ground connected to the Arduino's GND and have basically removed any "switching" from the equation... hence, my need for someone to point me in the right direction.

For the NeoPixels it was much more straight forward, because you always feed +/- right into the strip, and they only light up because of the data received. Basically, I don't have that 3rd wire here... these are just normal 2 wire LEDs.

Really appreciate any help, thanks!
Stephen

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Re: Help powering LEDs via external 5V source, instead of Ar

by franklin97355 on Sun Aug 04, 2019 8:32 pm

If you are trying to control regular LEDs rather than Digital LEDs like Neopixels you need some power management like a transistor or MOSFET. This might help. https://learn.adafruit.com/rgb-led-strips#wiring

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Re: Help powering LEDs via external 5V source, instead of Ar

by atomickid on Sun Aug 04, 2019 10:15 pm

Thanks for the help. That got me in the right direction. Went through some posts and found a good Mosfet tutorial, for anyone else. https://bildr.org/2012/03/rfp30n06le-arduino/

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