Connecting motor starter directly to photoeye?

[matlark]

I want to stop a process with two motors when an object is detected. Is it possible to just wire the PE output to the starter coil ( vs. running through a plc looking for a change)? It is an automation direct PE 1451e-6514 with Specs of PE: output load is 3A @ 120VAC

thanks

 

[bdr1234]

If you set the drive for single-input control (i.e. signal high = OFF, and signal low = ON), but how would you operate the drives otherwise? They would always be on when nothing is in front of the eye (or vice-versa). More importantly, what if the object passes through the photoeye before the drives come to a complete stop. The drives would then start up again. More importantly, I don't think anybody in safety would allow this type of control of a drive. Having the PLC allows you to set modes, start/stop control, AND photoeye part detection.

Maybe I misunderstand your question though.

 

[matlark]

There would be no drive, just a starter (coil). This would be for a test environment so it would not be out on a floor anywhere. As long as the PE is not blocked the motors would be on, when blocked motors disabled. Would have a disconnect to cut power to the motors but I want the PE to control the starter coil. If the output load is rated at 3A, controlling 2 starter coils should be possible correct?

thanks

 

[brucechase]

For testing purposes, you should be able to control the starter directly (depending on the size of the starter). Not knowing exactly what make, model, and/or size of the starter, as long as you are NEMA size 1 or less (they pull around 2A inrush), you should be OK. Depending on the size of the starters, you might not be able to control 2 starters with 1 Photoeye. Look up the manufacturer of the starter and look at the inrush current at 120 VAC.

The Photoeye is a relay style and for longer life, you could put in a surge suppressor. But if this is a proof of concept, you should be OK. Make sure you fuse the control circuit at around 3 amps and you should be extra safe.

 

[OZEE]

Personally, I'd connect the photocell to a relay, then connect the relay to the starters.

 

[brucechase]

Personally, I'd connect the photocell to a relay, then connect the relay to the starters.

OZEE - that photoeye has an isolated relay built in.

 

[OZEE]

3A output still worries me. If the starter is small (< NEMA size 1) you're probably ok. With two motors, they better be size 0. Otherwise, I still want a relay to give me at least 10A.

 

[Lancie1]

As long as the PE is not blocked the motors would be on, when blocked motors disabled.

What is the switching frequency? For example, if the photoeye is looking at packages on a conveyor, and they pass at 1 per second, and your photoeye is going on/off 1 time per second, then I think using the photoeye to directly control a motor starter is not a good design.

In most cases that I have seen, I was never able to use any photoeye input directly to control a motor. It always seemed to need some timing function in conjunction with the photoeye: If it stayed blocked (ON) for T seconds, THEN maybe I started or stopped a motor.

What about STOP switches? Have you made provisions for someone to stop this motor when (not if) something goes wrong - photoeye fails, or gets knocked out of position so it never stops the motor? If you wire it directly to the motor coil, then you will have to cut the main power to stop the motor.

 

[matlark]

Thanks for all the replies....I will just run it thru a PLC we have sitting around. I was curious if I could control the starters with no PLC (just using the PE), and in certain applications it is good to know it can be done. I'll repost when it is all set up, and/if working (it is for testing).
thanks

 

[leitmotif]

Thanks for all the replies....I will just run it thru a PLC we have sitting around. I was curious if I could control the starters with no PLC (just using the PE), and in certain applications it is good to know it can be done. I'll repost when it is all set up, and/if working (it is for testing).
thanks

Yes you can wire teh photo cell in the control circuit with no PLC needed. Just like it was done in the century (almost) before PLCs. As said you will need to ensure the eye can handle the surge current of the motor relay.

Interesting how quickly old techniques and technology get forgotten. While ago in class I teach a young student asked what is that round thing you are using in the light bulb circuit? It was a glass screw in fuse that was near universally used pre 1950.

Dan Bentler

 

[OZEE]

what is that round thing you are using in the light bulb circuit?

A penny??

 

[leitmotif]

A penny??

Was doing demo on series circuit using 60W bulbs. Showing what happens with increasing / decreasing resistance / voltage change and all that "basic" Ohm Law stuff.

Students included journy electricians who asked why did they not teach us this way when we were apprentices? It is so apparent - I now have a better understanding. I consider this a complemtent.

Used fuses to replace lamps.

DID not use pennies because
1. Did not even consider them
2. On more thought --too hard to get out of lite socket.
3. I am supposed to be teaching GOOD electrical practice (at least I think so)
4. Fuses easier and quicker.

Dan

 

[brucechase]

I will just run it thru a PLC we have sitting around.

Guess I should stop answering questions.