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I've been trying to connect my LED stripe -> rgb amplifier -> Arduino Mega 2560 -> PC. After connecting it according to this guide, nothing happened.

Looking inside the amplifier I noticed the three 5.1V Zener diodes. Using a multimeter I discovered the 5V from my Arduino only carries ~3.8V to those diodes and it consequently stopped there. Shorting out either diodes made my lights glow (and it only took me a few hours to get to that point..).

circuit

Now it seems I have two options:

  • Sending it back and order another one which hopefully uses different diodes
  • Using a soldering iron and short them out myself

Is the later even an option? Are there any safety issues?

Is there something else I can do?

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If they are protection diodes, and you short them, that means you will short the input to ground. The right choice would be to remove them if you don't want them. However, I highly doubt this is the real problem, assuming the board is even half-way competently built. –  Jon Watte May 13 at 16:37

2 Answers 2

This type of "amplifier" is designed to accept a 12-24V control voltage from another LED driver. The 5.1V zeners give it a bit of a threshold voltage (6V or so). They have no other function at all.

You can safely short those diodes if using a 5V logic-level drive.

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By the control voltage, do you mean the '+' on the left upper corner? –  Dzarda May 13 at 18:56
    
The voltage(s) applied between the '+' on the left upper corner and the three RGB inputs are the control voltage inputs. –  Spehro Pefhany May 13 at 20:11

It is a horrible layout. Nevertheless these diodes are supposedly there to protect the isolators from inputs higher than ~5.1V

↑ Wrong ↑

They can be shorted, provided that you don't up the input voltage too much.

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Could you expand on the "horrible layout" comment? If the diodes are not connected as shunts to ground, how are they supposed to protect the circuit from over voltage? –  horta May 13 at 17:38
    
It looked to me that they're wasting space largely. Then I realized it's probably supposed to fit in a specific casing. I'll edit the question to fit reality better. –  Dzarda May 13 at 18:54
    
The more important thing is that if the diodes are the red things off of the + in the schematic, then it's impossible for those to be used as an over voltage protection because they're in series with the circuit rather than shunting. –  horta May 13 at 18:57
1  
In my opinion it does provide sort of overvoltage protection - not by shunting, but rather acting like a voltage drop. But yeah, probably as Spehro pointed out, they're there just to make it work from 12-24 Volts. –  Dzarda May 13 at 19:10

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