Losing voltage at E stop

[wade88]

Hi lads,ladies

I have just put together an E stop circuit that is integrated into an auger motor control circuit w/ forward/reverse DOL. I have posted this awful diagram on another post but i am having some trouble when i put 24v down the + line and getting a readying of 0V as soon as it hits the first E stop.

I just drew this up really quickly yesterday to give a better idea of what im looking at.



The 24V signal will actually be supplied by the PLC module, but the PLC chap has yet to come in and finish off his work so i wanted to just test mt circuit prior to his arrival and put 24v down the line. I was getting a voltage until it hit the first E stop which is located on the side of the auger hopper.



I have a 24v DC mini contactor relay in the adaptable box with the E stop circuit coming from the A1 and A2 ports in tri-rated 18AWG cable, the circuit continues round to the second E stop the other side of the hopper and then will carry on to the PLC when its ready. When the PLC calls for product it will send the 24V signal through the line, through the E stops and onto the contactor, energising the coil and closing the circuit. That's the plan

But like i mentioned, even after putting 24V down it, simulating the PLC signal, when it hits the first E stop, i just lose voltage, and get nothing?

This isn't the sort of work i do everyday, and is my first E stop circuit. I posted previously regarding this topic and received from very useful feedback from a lot of guys regarding its design etc, so would really appreciated a little more on this matter.

Am i missing something really obvious, i may have missed a lot out in the description so i apologise if your short on info. Just ask and i shall try and answer you.

Cheers lads, Ben

 

[wade88]

Be gentle Tony

 

[Spoon]

I take it that you have done it this way cause the rist assessment says there is no risk to human injury?
I also take it that there are N/C contacts on the stop buttons and not N/O, as shown in your diagram?

 

[Fast&Rough]

You should put the e-stops in with the start stop controll that brings in the contactors instead of adding in another contactor. what else is the plc controlling its usualy just an input sent back to the plc giving an Id on which e-stop has been activated

 

[wade88]

Yes N/C contacts, Im a bit of a boob, but not a total ---

I personally believe there is little to no risk of human injury yes after carrying out my own risk assessment. But wanted to put the E stops in anyway. Should i have done it another way?

 

[wade88]

You should put the e-stops in with the start stop controll that brings in the contactors instead of adding in another contactor. what else is the plc controlling its usualy just an input sent back to the plc giving an Id on which e-stop has been activated

Yes that was the original plan, but the start stop control as pictured, which is what we wanted, was not available with a 24v coil.

 

[Spoon]

Are the guards Fixed or Interlocked?
If all is well with the risk assessment then you only need to use one of the two N/C contacts on the EM stop buttons.
Scrap the ones off in black and then try again. Check the continuity of the contacts to see if they are ok and functioning correctly.

 

[Spoon]

I think what F&R is getting at is to put the EM stop contact in series with the Stop button on the start/stop.
That would have been better.

 

[wade88]

Well i have wired them as such, + to terminal "1", - to terminal "2" and so one then just daisy chained on to E stop number 2, same terminations in that switch (only using one of the N/C contacts on each E stop) and then out to the PLC.

 

[Spoon]

Are the guards Fixed or Interlocked? Important question.
So you have 4 EM Stop Pushbuttons. Is it wires like this: (done in a rush)

 

[stef]

Yes that was the original plan, but the start stop control as pictured, which is what we wanted, was not available with a 24v coil.

Careful with that, wade, look at the machine safety directive: safety has to be separated from start/stop circuit, if it is a new design you must include a failsafe device. Therefore a second contactor is needed, one for the safety, one for start/stop. I was in a similar dilemma a while ago, Tony gave me some excellent advice. To cover your own butt, make sure that you are compliant, whatever you do.

 

[Silly Sausage]

Be gentle Tony

I do like an optimist!

 

[Fast&Rough]

Pilz 2 channel safety relay

 

[wade88]

Careful with that, wade, look at the machine safety directive: safety has to be separated from start/stop circuit, if it is a new design you must include a failsafe device. Therefore a second contactor is needed, one for the safety, one for start/stop. I was in a similar dilemma a while ago, Tony gave me some excellent advice. To cover your own butt, make sure that you are compliant, whatever you do.

It is a seperate contactor for the safety circuit mate. Main start/stop contactor is in the main box.

Spoon, thanks for making better clarity of my awful drawing, i have 2 e stops, i just drew it badly as i don't know the correct way to drawy diagrams i apologise. So i only need to take one feed from A1 across the E stops? and then take that feed back to the PLC? I just assumed i needed a + and -. my inexperience getting the better of me again.

 

[KAS1]

That cable tray is ****...e

 

[wade88]

I think i have been a total fool. I have over looked the insanely obvious....... i shall take myself outside and beat myself with a cricket bat.

 

[Silly Sausage]

I applaud your thread timing Ben....during Tony's afternoon nap! :smilielol5:

 

[Robotstar5]

I'd replace the contactor with a safety contactor, use an N/C aux contact in the reset line of a safety relay. The safety relay would monitor the E-stops and the PLC feed to the contactor coil would go through one of the safety outputs, 13-14 etc.

 

[Brightspark2]

To improve the tray mount it on brackets rather than straight to the wall, then you can get cable ties behind. Also manufacturer the top bend rather than just sticking two piece's side by side. Will look a lot better and more professional.

Now I'm not calling your work as I don't like doing that, its just tips for next time :daisy:

 

[vaughant]

Wade don't wind yourself up about it mate,a basic stop start circuit is a question my boss (now former) added to the archer trade test and apparently the majority of sparks got it wrong,which for a control man like me is scary but then again I'd never made off a barrier gland until my last trip offshore so it's different horses for different courses.

But basically your e-stops are just a daisy chain in line to your a1 or coil + on the contactor.

Generally pilz style relays are used as its harder to bypass them but not impossible.