# Arduino not driving RGB LED Strip

I'm using Arduino Uno with a 12V RGB Signal Amplifier and a 12V RGB LED strip. 12VDC is supplied to the amplifier.

However the LED strips does not light up whether the PWN pins are set to either 0 or 255.

   analogWrite(ledPinR, 255);
analogWrite(ledPinG, 255);
analogWrite(ledPinB, 255);


When set to 255, the OUTPUT R,G,B pins have a voltage of 6.3 V to 8.6 V, while the INPUT R,G,B pins are about 4.7 V.

The OUTPUT pin voltages does not change whether the INPUT pins are at 0V or 5V.

The RGB strips light up when I connect the POWER - terminal to any of the OUTPUT R,G,B terminals.

What can be done to allow the Arduino to light up the LED strips?

• What happens if you disconnect one of the amp inputs from the Arduino and connect it to +5V? – John Honniball Nov 14 '14 at 0:05
• @JohnHonniball Nothing happens. The LED strip does not light up – Nyxynyx Nov 14 '14 at 0:06
• Actually the OUTPUT voltages does not change when the INPUT R,G,B voltages are changed from 0V to 5V. – Nyxynyx Nov 14 '14 at 0:15
• Sounds like +5V isn't enough to activate the input. Maybe, as others have said, it's an entirely 12V device. Or there's something else that we haven't spotted yet. – John Honniball Nov 14 '14 at 15:35

From what I can see this little box is designed to take a 12V low-current signal and amplify it to a 12V high-current signal.

It is not suitable for directly connecting to an Arduino.

You will need three NPN transistors to connect between V+ and each of the R, G and B inputs, and then drive the bases of the transistors through a resistor from the Arduino.

But that's only a wild stab in the dark since there seems to be absolutely no documentation available anywhere.

After much hunting I managed to find this image:

so it seems it is designed to go midway through a chain of LEDs to power more of them, not be driven by a low voltage device like an Arduino.

• I disconnected Arduino completely from the amplifier, then connected PWER +12V to INPUT V+, and POWER +12V to INPUT R,G,B but the LED strip still does not light up. Does this mean there's also a problem with the amplifier? – Nyxynyx Nov 14 '14 at 0:31
• I notice RGB Controller in the diagram. That probably outputs 12V signals? Heres another wiring diagram that includes Arduino: arduino.stackexchange.com/questions/3535/… – Nyxynyx Nov 14 '14 at 0:33

This has been a problem posted on several blogs and forum's - the solve is usualy quite simple. the Amplifier is actualy grounding the negativ R G B points from the LED strip. Thus it does not require 12v as sutch. and the initial sketch of connecting arduino 5v pin to the 12v rail of the amplifier is a sure path to burning your arduino -FAST.

Solve is to remove the 12v from the amplifier. most of them work fine with 5v.

• Do remeber that as you use two Voltages both have to have the GND as common. both minus 12v and minus 5v hooked to same GND. – Erik m j Sep 3 '16 at 10:05
• Welcome to EE.SE! This seems plausible, but depends on the device. However, you've now connected 5V to a 12V input on the amplifier device. You also haven't indicated connected the Arduino's power to an appropriate source. Consider using the schematic editor to draw your own diagram. – user2943160 Sep 3 '16 at 15:13
• Thank you. I ommited to elaborate on the 5v. Thanks for pointing this out. Most of the rgb amplifiers has the 12v bridged. And a diode to limit power to the internal (switching circuit). Check your Amplifier before connecting the 12v. My point was to use one 5v powersource for the amplifier and arduino. And a 12v powersource directly to the LED strip. Both sources with a common minus. I have made several setups like this and never burned arduinos due to 12v going where you dont want it. See my editing of treadstarters drawing, abow. – Erik m j Sep 4 '16 at 17:27