STC microcontroller through the relay control AC motor, in the motor start and stop the moment will be interrupted multiple times
If the interference is very serious, you can consider using no relays to control the start and stop of the motor, using SCR to start and stop, so that the power supply of the microcontroller will be much less interference
The first floor is very good. Let me add a few points.Look at your description, estimate the problem in two aspects, according to the single-phase motor1, relay pull in, release contact sparks interference.2, if it is similar to the pistol electric drill motor, before the stability of the speed, interference is great.The interference way, is the signal of the photoelectric sensor inside the amplification part, the interference (crosstalk) signal as the normal signal amplification, so even if you are shielded, the interference signal is transmitted through the normal channels, so it can not be excluded.Recommendations: 1, replace the better performance of photoelectric converter, or photoelectric converter itself shielding; 2, according to the speed change into the appropriate proximity switch, Holzer principle, there is speed sensor. Of course, as the first floor said, SCM software anti-interference, and choose the right working model is also essential.
You've taken some of the usual anti jamming measures, but the key issues haven't been solved.1, the relay is isolated, without individual power supply, the photoelectric coupler input, if need to power (such as 6N137), must be separate power supply.Signal 2, optocoupler out, if it is low speed optocoupler, decreased along with gentle, easy to false triggering, you can add a Schmitt trigger in optocoupler after. It should solve your problem.3, SCM procedures can also do some anti disturbance processing, for example, some of the microcontroller's external interrupt, anti disturbance processing, you can open. If not, you can use the query operation, for example, each 10uS query IO once, 5 times continuously high, think that it is effective to obtain a high level, high level, set a mark, marked effective, inquiry into the 5 consecutive low level (if the middle high level again just count) is deemed effective falling edge.
