rgb led amplifier to control strip via arduino

EDIT: btw, please excuse me, if I posted in a wrong board, I am hoping this is the right one, but not sure anyway :slight_smile:

Hi guys,
I am currently trying to use a RGB amplifier as än interface between arduino and a led strip. I did everything (well most of it) by this instructable: instructable

And found out it doesnt work. To me it seems that 5V is not enough to turn the amplifier circuitry on.


heres a shot of how I connected everything up. HIGH RESOLUTION HERE

Later I found out that if youre using the barel jack to power the arduino, you can use VIN to supply voltage to an external component, so I thought 11V (or so I have in jack) would be enough to open the amp circuit.

Now the problém is a little different to the one before. I can control the strip ok, but now I cannot turn it completely off.

If I choose one color and turn that one by software, the other colours (although they should not light at all) stay at about 50% lightness, aka I can measure on the other colours like 6V.

It seems that when the pins 9,10,11 act as a ground to the circuit they cannot sink more than 5V? Is that so?

What can I do? How can I make it work? Thanks a lot everyone, I am desperate! :frowning: :slight_smile:

also heres a small schematic of my first try

I changed just the 5V to VIN...sorry that its in czech language (the notes on the schematic), but I thought someone on czech boards would help me...:slight_smile:

and havent :slight_smile: so please, help mates :slight_smile: thanks in advance

First off remember that nearly all electronic circuits on instructibles are crap, never ever make anything from the site unless you know more that the person who wrote it.

What is that RGB Amplifier? It looks different than the one on the instructable site. Can you post a link to the data sheet of the one you have.

It seems that when the pins 9,10,11 act as a ground to the circuit they cannot sink more than 5V? Is that so?

I am not too sure what you mean by that, but an arduino pin can only sink 40mA or less. Talking of sinking voltage makes no sense. You should not let the arduino pin be connected to any more than 5V otherwise it will be damaged.

Hi and thanks for your reply

here is the datasheet

well I might have phrased that part a little wrong...well I will try to explain in a different way.

When theres one color at full and all others at no intensity (in my code), the color which is at full (lets assume red), will give a reading of 11V on multimeter (measuring VIN - to pin 9)
green and blue will give a reading of 6V...these pins are configured as outputs and are sending pwm out.

VIN is used as the plus for the input of the amplifier.

(yes now I see that I should not have gone the instructable route)

any idea now? :slight_smile: thanks in advance.

is that really so, that the pins will be damaged now I have tried it this way? Or is it ok?

(measuring VIN - to pin 9)

Why?

You normally measure voltages between ground and another pin, in that way the readings are instantly understandable.

is that really so, that the pins will be damaged now I have tried it this way? Or is it ok?

If you put more than 5V into an arduino's pin it will be damaged. But have you done this. Disconnect the RGB amplifier's inputs from the Arduino and measure the voltage between ground and the amplifier's input.

Grumpy_Mike:
Why?

You normally measure voltages between ground and another pin, in that way the readings are instantly understandable.

Hi,
well it's because what goes into the amplifier, aka + to the amplifier input is from VIN, and - is from pin 9 (or 10 or 11 for each color) hope I make some sense now.

So I should measure what's between a GND pin from arduino to what? :confused: I am confused now, sorry :frowning:

well it's because what goes into the amplifier, aka + to the amplifier input is from VIN, and - is from pin 9 (or 10 or 11 for each color) hope I make some sense now.

Sorry makes absolutely no sense at all.

So I should measure what's between a GND pin from arduino

Yes.

to what?

To the 3 inputs of the RGB amplifier when not connected to the Arduino to see if the inputs float to a value higher than 5V. You still need all the grounds connected together and the supply to RGB amplifier also in place.

Hello Mike,
thanks for all your help, but in the end, I decided to give up and built it with mosfets...thanks anyway, much apreciated!