pudge565

My shop teacher would like to find a ladder diagram for a float switch with a start stop button override. He is not able to draw a diagram that would work. Please help with this.

Edit: To make it more clear he wants it to be that the float switch does not have to be closed for you to turn the motor on with the start stop switch.

luminous

seems to me all you need to do is add a relay with the float switch on the nc contacts and add the start/stop with the relay on the holding side of the circuit,,it can get more elaborate than that , but that is basics, for safety reasons you want to take the float switch out all together while you are in a manual mode,of course there would be a selector switch added,,,wish i could draw it for you,,i'm sure someone here knows how to post something for you

luminous

I would draw you one up, but I dont even know how folks are putting them smiley faces on here,,sorry x i would put one with a sad expression where the x is.

stars13bars2

What he needs is a hand-off-auto switch. This allows power to be switched from the on off switch to the float switch, or have both turned off.

John Valdes

Whats he doing teaching this class. I mean no disrespect, but if he can't draw this simple circuit, why is he teaching a class on electricity.

Same here on posting a drawing. But I can do the smiley faces.

pudge565

He never really had to do this situation. It is out of a book that gave him the materials to use but no ladder diagram.

pudge565

That is the problem this is on an ancient lab volt trainer. The float switch only has 2 sets of NO contacts.

luminous

ok,I can understand the one set of n o contacts your control voltage runs through them and when the float switch is mechanically activated turning those n o closed completing the circuit, which could be inline of the holding circuit on the starter telling the motor to pump some out,once brought down to the next level using another type of float,or actuater,proximity,etc,that will through the use of external,or internal,(plc) relay,will reset the process,the ladder logic is quite simple, and the most common method of seeing this is with a 3way selector switch,and in most applications there will be another motor/pump waiting on the go ahead to start filling back up,,so there will be safety precautions taken through the field wiring,as well as the plc program,like using the auxillarys on the starters,is this a plc class your in?

mattsilkwood

What is the list of materials that you can use?

lectricboy

http://s707.photobucket.com/albums/w...oy%2FFloat.jpg

I think this what you need.

Toronto Sparky

A push-pull start switch or better yet a hand-off-auto selector switch.
A regular stop start switch would require a magnetic contractor assuming the motor isn't already controlled by one.

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pudge565

My teacher and I think that we have it figured out at this point. I will post a link to the diagram I made when I am at a different computer. My computer is a POS.

lectricboy

I hope this link works. I messed it up the other day.

<a href="http://s707.photobucket.com/albums/w...nt=Float-1.jpg" target="_blank"><img src="http://i707.photobucket.com/albums/w...oy/Float-1.jpg" border="0" alt="Float"></a>

pudge565

Here is the drawing I made.

Float Switch.bmp

PapiMayito

yeah

Ray Cyr

I see a couple of problems with this circuit. First, the relay and motor starter are in series, this probably won't work. Second, the pushbutton stop switch and the float switch are in series, if the float switch is closed the motor can be stopped using the stop pushbutton but only as long as the button is pushed.

pudge565

We don't want to be able to shut the motor off if the float switch is closed. It was the way I worded it. As to the diagram I will redraw it to fix the control relay.

Ray Cyr

Another small note, I don't know what you have for components but it is likely that the motor starter will have a set of normally open contacts that you can use to latch the circuit closed around the normally open start pushbutton. This would eliminate the use of the control relay.

John Valdes

This is how I would have drawn this circuit. I did not draw the OLR. I usually put it between the starter coil and the neutral. Yes, the neutral.

Attached Images

Float Switch-1.bmp (98.1 KB, 25 views)

pudge565

Ok I had misunderstood the instructor. He does want it to over ride the closed float switch. That way if it stuck closed and was pumping dry you could shut it off.