I'm controlling a small motor with an Arduino Rele board. However, even though it is working, when checking the VCC and Control signal with the oscilloscope, I've found out huge negative spikes when it turns ON and OFF. The spikes go from 5V to -0.2V then back to 5V in 115us.
Also, you'll see that there is a little delay due to the relay being a mechanical device, so it takes around 5ms to toggle it.
Nice that things work but as well as You that spike looks odd.
Can You post a wiring diagram of power and signal cables?
What takes place at the time the spike occurs some 5 ms later then the low going signal?
Is the motor having brushes?
Most looks good to me.
There's a cable between J1 and J2 I don't understand but it might be unimportant.
The LED1 will lower the current through the opto coupler light emitting diode. Skip it? The value of R1, 1 kOhm looks a little bit too high to me. Try 470 or less? Check the opto specs for max current!
How is the controller supplied? 5 or 12 volt? Must be 12 volt to Vin. 5 volt must be to Arduino +5 volt pin.