Limit switch reversal of travel

I have 2 limit switches on a test machine that travels back and forth using a stepper motor. Maximum required travel is +-0.375" from centerline. The limit switch currently shuts the power off.

I want the OPTION to CYCLE the machine from left to right without user interface. But I still need the option to stop at that limit switch too.

The machine is 110V Single phase. It has a toggle switch for direction of travel and a stop button.

What would be required to required (in general) to rewire my machine.

Thanks Pal

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Be a great nano PLC control project + FWD-OFF-REV motor starter. Could count cycles and other thing then too. Maybe a Keyence or other NANO PLC.

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You didn't mention any PLC control, so I take it that your systems is hard-wired. Without any detail of the travel limit switches available I would use these switches to switch a double pole relay to reverse the motor's direction. Another series-wired switch should kill the power to the whole system. This is the cheap solution.

An elegant solution would be to use a micro PLC like mentioned before. I also see these days that you get intelligent relays on the market, even a better solution from a cost point of view. Amongst others, try the Mitsubishi Alpha series or Moeller Easy relay and the cheapest I found is the FAB Giant relay.

Keep us posted.

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When I've done this sort of thing (with DC motors) I set up my drive circuitry/software to only be able to stop or drive out of the limit switch, not drive in. This is fairly easy to do if your control circuit has a drive-in line and a drive-out line; you can do it with a few gates. Having no idea of what you're actually using to drive your stepper I can't say much more.

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Tim Wescott

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