Hi all,
I have a problem with my project using 5v 4 channel relay module. I am using sensor to trigger the relay whenever I try to energize it. relay outputs were connected to 24v contactors to drive the motors. each relay has its own input signal coming from the Arduino output pins. basically each sensor will drive its designated motor. during testing, the relay energizes as what I've expected base on my program but without the connection of contactors. when i tried to connect the contactors, the signal scrambles. relay 1 energize together with relay 2 though I only tough 1 sensor. Could it be because of High current of the 24v contactors? Please I need your help
Yes, this is likely to be EMI from the high current circuitry - this could be due to poor layout of the wiring
and it would be useful to see a photo/diagram of how everything is laid out. Lack of snubbing or
freewheel diodes could be an issue too.
You can also get mains spikes from the circuit being switched which propagate through the power supply for
the Arduino.
Details of all the hardware should be posted, motors, contactors, relay module, etc... Otherwise we'll just
have to quiz you again and again for pertinent information. Links to datasheets and product pages preferred.
Thanks sir,
btw, I attached a wiring diagram of my project. the contactor I use was allen bradley100-c16*400 (see attached photo).
This contactor will drive the Dayton industrial motor Redirect Notice
and motor speed controller Redirect Notice
which controls the gear motor speed.
as shown on the schematic diagram attached, when S1,S2,S3 were off 4 channel relay function properly. And when I turned it ON the, switching signals from the relay becomes abnormal. It doesn't sync on what sensor I have touched.
please advice if I made a mistake on my connection. I need to know what causes this bug and what would I do to fix this. Is their other alternative ways or device to be added on the connection? I will appreciate all your response 
Thank You,