First of all, hello, this is my first post here. Sorry it's so long, but it's a pretty specific question that, A: I'm not sure exactly how to ask, and B: haven't been successful in finding a good answer to.
I have a G0602 lathe that I'm adding a tachometer to. The lathe uses a contactor to de-energize itself when the e-stop is pushed, and a pushbutton to close the contactor and power the lathe up again. A simple 3-position rotary switch controlls FWD OFF REV. The lathe uses a 110VAC, single-phase motor.
I am adding a PLC controlled, optical-interrupt tachometer with LCD readout that I made. It is powered by 5V DC power supply that runs off of 110VAC. I want the tachometer to be powered on/off with the lathe and not have a separate switch.
My first attempt was unsuccessful. I wired the DC power supply up to the load side of the contactor. The tach works perfect, except every time I rotate the switch from OFF to FWD, or FWD to OFF, the PLC resets. I'm not sure what's happening, but I belive it has to do with sharing the load side of the contactor with the motor, even though the motor has start and run caps.
For my second attempt, I found another identical contactor, new for $15. I plan on having them share the same line voltage and wire the e-stop and start buttons in parallel to both contactors. My goal is to isolate the AC motor from my DC power supply.
My question is, is this the best way to do this, or will I still have the same problems?
Thanks,
Daniel