Arduino fan control circuit help purrrlease!

Hello folks, I've been working with Arduino's for a little while but could really really do with an urgent quick 2nd opinion on the attached circuit. I hjave tested most of it but its the 4N35 I have not had a chance to try and need to know if I have specced and incorporated it correctly.

I have have researched and tested as much as possible but TBH its stretching the limits of my knowledge a bit :wink: The motors are two 24 volt 13 watt fans. The control signal is remote just on or off, the Sketch then uses this to switch from one fan to another with timers. As the control signal may be coming from some way away I thought it best to use an opto isolator in case of spikes. Not used one before so hope I got it right. Comments very much appreaicted please, pretty please! Many thanks in advance Fiddian

That's not quite right around the opto isolator.

Put the 10K in line with the supply to pin 5. Connect Pin 4 directly to ground. Connect pin 5 (as well as to the 10K) to the Arduino pin you want to use to monitor the signal.

Put a 20R (or so) resistor in the gate lines of the FETs to protect the Arduino's output from inrush current when first switched on.

Add some 0.1uF ceramic capacitors across the 10uF ones you have already. Loose the 100R resistor.

Many thanks Mike, very much appreciated.

Fiddian

Hi Mike, revised drawing. This look OK? thanks again.

all best

Fiddian