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Topic: Controlling Several different single 12v LEDs from arduino outputs (Read 425 times) previous topic - next topic

450nick

Hi all,

I am trying to use an arduino to control some switchgear from my car, and the switchgear uses 12v LED indicators, mostly singles but some double LEDs. I'm wondering what is the most efficient method of using arduino to switch on and off these 12v LEDs as required? I'm not sure what component to use - I'm designing a PCB so ideally something with small footprint as I will need to control a total of something like 20 separate warning lights so want to try and avoid a huge board full of transistors and resistors if possible... Is there a neat way to do it?

A direct driver would be a ULN2803, if you want a driver with a build in shift register something like NPIC6C595 can be used.

450nick

amazing, I had no idea they existed thank you!! What is a shift register and why might I want one..?

amazing, I had no idea they existed thank you!! What is a shift register and why might I want one..?
A shift register means you need 3 outputs from a microprocessor to control nearly any number of outputs.
You shift the bits out one at a time using a clock line and when all bits are out you toggle the latch line and all outputs will update.

450nick

Ah that is clever.. I think the first one will be perfect for what I need though - thanks very much for the info

450nick

Wait, there's another problem... On one of the other switch plates there are lots of LEDs, and they seem to all be fed by one of these transistors (any idea what the operating voltage is?) http://www.farnell.com/datasheets/43606.pdf

It seems for these LEDs that I need to switch the ground to light them. What's the best way of doing this with arduino?

Thanks!

Wait, there's another problem... On one of the other switch plates there are lots of LEDs, and they seem to all be fed by one of these transistors (any idea what the operating voltage is?) http://www.farnell.com/datasheets/43606.pdf

It seems for these LEDs that I need to switch the ground to light them. What's the best way of doing this with arduino?

Thanks!
That transistor is not for driving only a led, it can drive a lot more.
The ULN driver I listed switches to ground, you can get them both in 7 and 8 output versions:
ULN2803: 8 Open collector output
ULN2003: 7 Open collector outputs

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