Arduino causing DC supply to buzz?

I am new to the Arduino Uno. My class is building a square wave inverter with 4N37 Optocouplers and supplied by a DC supply (12V). The Arduino seems to be causing the DC supply to buzz and limits the Voltage. As I increase past about 6 Volts it starts to buzz and the Voltage won't rise anymore. If I disconnect the Arduino the DC supply works normally. There is some sort of interaction between the two that is causing the issue maybe. Any thoughts? Thanks.

What specifications have you got for the DC supply? How much power is the supply designed to put out?

You're using the arduino to control a switch, right?

So if the arduino is switching something..... then how do you know that the arduino is the direct cause of the issue? But, then again, since you're switching, then maybe issue is the switching itself.

Probably best to show a circuit diagram for your system.

You have reached the current limit of the supply I think.

I don’t know for sure that it is the Arduino. With the Arduino removed the gate on the MOSFETs wouldn’t
trigger so maybe it has nothing to do with it, I don’t know. I did set a limit of .075A for the DC source so maybe that is the buzzing. I turned off the supply and tried it again (I assume that killed the preset limit) and the same thing happened. Attached is my LTSpice schematic. I was told by another student that perhaps I need a separate ground for the Arduino side and the inverter side. Doing some research makes me think that is not correct. Thanks for the input everyone!

Square Wave Inverter - Gate Driver.PNG

Square Wave Inverter schematic.PNG

Are you certain there is no period where gate drivers 1 & 4 or 3 and 4 overlap even briefly? This can happen, for instance, if you've assumed that sequential digitalwrite() statements are simultaneous, rather than being separated by a few microseconds as is the reality.

Your opto coupler is slow, remember, its a photo-transistor opto coupler and with only 2k pull-down
in your gate-driver-1 circuit that looks like 20us turn-on time for your high-side FET.

Why are you using both n- and p-channel devices BTW? That's not the normal way to do this which
is with all n-channel devices and MOSFET H-bridge or 1/2 H-bridge driver chips.

0.075A = 75mA

You've got 12v across a 50 ohm load, for ~220mA of current.

So you had set the current limit on the supply to less than the expected load....

0.075A = 75mA
You've got 12v across a 50 ohm load, for ~220mA of current.

Yeah...... a quarter of an Amp peak current values, while current limit is set to 3/40th Amp. That definitely needs addressing.

Welcome to the forum.

If this is a class project and you have built it, you should now be trouble shooting with an oscilloscope.

Can you please post a proper circuit diagram, showing your power supply, transformer and labels on pins and components please, in CAD or a picture of a hand drawn circuit in jpg, png?

Tom... :slight_smile: