RGB LED's and ULN chip

[MurrayJ]

I am thinking of buying one of the Picaxe 20M boards with the ULN chip for a project which will, among other things, light a few RGB LED's.

The ULN chip always confuses me with the output to 5v not ground, so I thought I should get confirmation before buying the LED's on which type I should get.

I thought common anode - is this correct?

 

[westaust55]

UNL chips and RBG LED's

If you are going to use a ULN2803 or similar chip, these pull the outputs to ground (0Volts).

So you will need common Anode type RBG LED's.

There are IC's designed specifically to drive these RGB type LED's and I am sure others will inform you about them.

However, I have not gone down a path of allowing PWM with an 8x8 matrix of RGB LED's that I am building - construction has been a bit slow but boards now assembles, just to wire up to PICAXE and test.

 

[MurrayJ]

Thanks Westy, I realise the limitations of the pwm, and I am not using a matrix, just four rgb leds, so I should have it easier.