wiring a proximity switch with motor

[davidohyer]

I'm trying to figure out how I can wire a motor with a proximity switch so that as the motor runs, when the proximity switch is tripped, the motor will shut off and won't start again until I flip a reset switch. The motor runs on 120 volts and draws a fairly large current. The proximity switch's rated operational current is 300mA and its no-load supply current is 1mA. I thought of using a relay along with the motor and proximity switch, but don't have enough experience to figure out what I need to do to achieve these results. Any help would be greatly appreciated. Thanks.

Davido

 

[davidohyer]

I forgot to include some of the specs for the proximity switch that might be useful when answering. I've included the specsheet as a pdf for download.

Davido

 

[jraef]

Are you using the prox to detect the motor shaft turning, or are you sensing something else having to do with the work the motor is performing?

That just covers the details of which type of relay you need to use, but either way you will need to use a relay of some sort. The motor power goes through a Normally Closed contact of the relay, the prox controls the relay coil power. The relay seals itself in through a second set of Normally Open contacts who's power is fed through a set of Normally Closed contacts on the the reset switch, meaning that once the relay is activated by the prox, it stays energized, cutting off the power to the motor. You must then break the relay coil circuit with the reset button to allow the relay to drop out and allow the motor to run again.

 

[davidohyer]

I'm kind of following your suggestion, and it seems like it will work, but I'm not quite sure how everything is going to be laid out. Could you sketchup some kind of diagram I can follow with the description? I drew up a sketch of what I understand it to be, but I think I've interpreted something wrong, because what I have sketched doesn't seem to make sense. Also, i don't know if it makes and difference, but as part of the design, I need to have the motor stay off, even if the proximity switch closes(or opens, as the case may be) until the reset switch is hit(it's a normally open switch that doesn't stay closed). To clarify a bit, as the motor is running, when a piece of metal gets close to the proximity switch, I want everything to shut down. Thanks for the quick reply.

Davido

 

[MacGyverS2000]

What is this for? You claim to be an M.E., but the only other post i see by you is how to create a very simple mechanical device... not something I would expect a practicing M.E. to ask...


Dan - Owner

http://www.Hi-TecDesigns.com

 

[davidohyer]

I'm just starting my first ME job, been on the job 3 months now, so still trying to get the hang of things. They don't give you very much practical experience in college, at least at my college, so I'm still learning a lot. This is for a fatigue tester. My company doesn't want to spend the money for a commercial fatigue tester, so we are designing and building our own. I'm just trying to figure out the wiring to go along with the mechanical assembly. Anyways, sorry I don't seem like a practicing ME just yet, maybe some day...

Davido

 

[davidohyer]

Just a side note, my other post that was referred to was made around 3 years ago, back when I was first starting in Mechanical Engineering.

Davido

 

[jraef]

OK, I guess I misinterpreted that you already had some sort of motor control circuit, maybe you don't. So here are more basics:

How do you plan to initiate the process? A Start / Stop Button? On-Off Switch? Some other Run signal from something else?

Is it a momentary or maintained contact?

How did you plan on stopping the process, other than the Reset button?

If someone stops it mid way through a cycle, how do you want to deal with it? Reset? Resume on restart? Require manual intervention?

How do you plan to re-initiate the process again under normal circumstances?

Does the motor return to a home position? Does it need to reverse? How would you do that? What kind of motor is it?

It sounds as though you are a neophyte on control systems, you may want to ask for help from someone experienced who can see your system and understand your application. I know you probably think this isn't hard, but it is a little more complex than you may have originally imagined. This forum is for working engineers in a particular field to share ideas, it is not supposed be a substitute engineer for someone working in another field. Sorry.

 

[davidohyer]

Thanks for the reply, I guess I'll have to ask around my company and see if anyone here has some experience with this sort of thing. Thanks for the suggestions, I'll try to keep future posts to the sharing of ideas rather than looking for a substitute engineer.

Davido

 

[zekeman]

What you need is a latching relay and your questions are quite appropriate for this forum, the criticism notwithstanding. Without your type of questions, there is no need for this forum.
How this works is the latching relay (having two coils) is in the normally closed state and one coil of the relay is connected in series with your prox switch. On prox switch closure, the relay contact "latches" to open turning and keeping the motor off until such time as the other coil of the relay is activated by a manual momentary contact switch which restores the relay to its former closed state, restoring the motor "on" state.