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davidh
11-02-2009, 06:03 PM
i have a push button to start, push another button to stop, relay controlled machine called a pullmax. i am currently trying to wire around a very complex 4 speed electric controlled shifting gizzmo that i completely removed as it is not working and has caused me hours of frustration. i am going to shift the 4 speed by mechanical means. . . but thats not the problem.
i cannot understand how the controller/relay functions so i can wire up the two button controls.
question 1 is: when you push the on button(normally open) its a momentary contact button and the relay clicks in. . . but when you release the button, what keeps the relay or coil clicked in ? is there a internal circuit in the relay that holds it in or ?????

then theres the question of the stop button. its normally open and of course depressing it shuts off the power to somewhere on the relay causing the relay to relax or disengage.

this is a three phase controller/relay and the control voltage is 110v, and im just completely mystified.

is there any pictures anywhere that someone can steer me to ? ? ? i hate running this thing using wood wedges to hold the relay closed. . .

thanks in advance.

davidh

Peter.
11-02-2009, 06:29 PM
There's a pull-in coil that you energise by hitting the go button. THis pulls the main contactors in. Alongside those main contactors will be a scondary one which will keep powering the pull-in coil all the while the power is on. Hitting the stop button cuts the power to the pull-in coil releasing the contacts.

fredf
11-02-2009, 06:38 PM
http://www.claytonengineering.com/Training/myweb6/Module19/Output/images/FIG_18.gif

In the ladder diagram on the right M is an auxiliary contact on your contractor the OL contact is from your overloads (assuming you are running a motor starter) you hit the start button and the contactor closes. the M aux contacts parallel the start button and keep the contactor energized. when you push the stop button you break the circuit to the coil and allow the contactor to drop out


i have a push button to start, push another button to stop, relay controlled machine called a pullmax. i am currently trying to wire around a very complex 4 speed electric controlled shifting gizzmo that i completely removed as it is not working and has caused me hours of frustration. i am going to shift the 4 speed by mechanical means. . . but thats not the problem.
i cannot understand how the controller/relay functions so i can wire up the two button controls.
question 1 is: when you push the on button(normally open) its a momentary contact button and the relay clicks in. . . but when you release the button, what keeps the relay or coil clicked in ? is there a internal circuit in the relay that holds it in or ?????

then theres the question of the stop button. its normally open and of course depressing it shuts off the power to somewhere on the relay causing the relay to relax or disengage.

this is a three phase controller/relay and the control voltage is 110v, and im just completely mystified.

is there any pictures anywhere that someone can steer me to ? ? ? i hate running this thing using wood wedges to hold the relay closed. . .

thanks in advance.

davidh

boslab
11-02-2009, 06:44 PM
a start button will 'pull' the coil, through itself and therfore latch, i.e keep energised, a stop button is a normally closed button inserted into the latch circuit that when pressed breaks the latching loop, emergency stops are the same, all made NC, never ever NO
have a look at a plc ladder diabgram, you will find the important elements of start, stop and emergency stop are always the first rung of the ladder [unless the programmer wants to make it difficult for others]
mark

derekm
11-03-2009, 02:53 PM
emergency stops are the same, all made NC, never ever NO
have a look at a plc ladder diabgram, you will find the important elements of start, stop and emergency stop are always the first rung of the ladder [unless the programmer wants to make it difficult for others]
mark
Not true... you can make one using another relay to invert the sense on switch from NO to NC

Falcon67
11-03-2009, 03:02 PM
>Not true... you can make one using another relay to invert the sense on switch from NO to NC


In order to wire the E-stop into my VFD control inputs, I had to have a NO switch.

boslab
11-03-2009, 03:45 PM
cant argue with that i aimed to be simplistic, i only do simens and mitsibushi
kind regards
mark

The Artful Bodger
11-03-2009, 04:16 PM
>Not true... you can make one using another relay to invert the sense on switch from NO to NC


In order to wire the E-stop into my VFD control inputs, I had to have a NO switch.

I would feel more comfortable with a NC stop button as I expect opening a circuit is more reliable than closing one and I would really like a stop switch that always does stop the machine.