I know there is a lot of info on protecting arduino from reverse currents & such, I have read as much as I can, I need help!
my problem:
I have a TIP120 driving a dpdt 12v relay to run an AC motor (fritzing diagram attached). The relay coil is powered by an atx power supply(12v leg). When the coil tries to switch the relay and turn the motor on, it clicks like the coil is energized and then the whole system resets. I also hear a pop through my speakers, which are not part of this circuit, but plugged into the same 120vAC line.
With the motor disconnected, the relay functions properly.
I find it a bit odd that this happens when the motor tries to run, as appose to when it stops....
I should also note: this does not occur every time, but certainly most of the time, often the first switch on works just fine (successfully runs motor).
This is normal because of electromagnetic interference caused by the initial magnetic field is inducing interfering voltages.
To reduce this you have to reduce the switch on surge This can be done with what is known as a snubbed circuit. Try googling it.
In my first post the circuit is drawn simplified, in actuality the relay takes place of sw1 in the circuit shown in the pic attached. the red box highlights something that looks a lot like what i see when I google snubber, more specifically "rc snubber". I never knew what the function of this was, I simply followed the manufacturers diagram, somewhere along the line, I had problems with the motor, removed those RC sections & it ran (manual switching).
So i figure I should re install those, would you expect that to resolve my problem, or do I need an additional snubber somewhere in the circuit?
also I see stubbed circuits that are very simple RC setups ranging to very complicated versions, will the simple RC do the trick?
Also you might try decoupling across the 12V supply near the transistor and diodes, you may benefit from it there - try something like 10uF to 100uF. Make sure all low-voltage wiring is well away from mains wiring where possible.
Your motor may high a high inrush current rating (if its an induction motor then the relay will have to be
pretty beefy to cope with the inductive load).
