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.

 

[Knobhead]

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

I'm awake now, unfortunately it's 02:00! I'm not even going to comment on this travesty. I just hope it doesn't develop in to a tragedy!

 

[wade88]

Yay Tony's here!

Brightspark, i did mount the tray on spacers, you just can't see them. As for the top bend, it's pretty ugly for sure. Bit of a tray noob, so ill do a better job next time.

Vaughant, thanks mate, i've got it down now, made a really silly error, really face slapping moment, but it's all good now.

Robostar, due to my lack of experience in this area, i didnt think to look to get a dedicated safety contactor, figured the one i have would suffice (which it will) although i appreciate it is not idea for the scenario, i will source a new contactor asap


Thanks again lads, really appreciate the feedback...and you tony, big kisses

 

[Spoon]

I thought one of your work mates was going to help with the design of this? One that has lots of experience in machine safety directive and safety circuits?
Again (just cause I curious and it is important) are the mesh guards on the mixer fixed (Bolted closed) or hinged (for maintenance)?
If there has been a full safety report and there is no chance of injury to people do you still need an Emergency Stop circuit? Could you just not use a Stop Circuit?

I quite understand why Tony is not saying anything.... I hope you are being supervised by your work mate who has experience in machine safety directive and safety circuits

 

[wade88]

My colleague is from a different company, he came down for a day to help me with a bucket lift conveyor i was having some issues with and then talked me through the design of this.

It's ok, i understand why people may be dubious to make comment, thats fine.

Bolted closed mate.

 

[Spoon]

Im just trying to help you out a bit mate and hope that you dont end up getting yourself into lots of trouble if things go wrong.
Its good that the guards are bolted closed.
When you did your risk assessment what Category of stop was needed for your design?

 

[wade88]

Yea and i appreciate it fella for sure.

Not really sure what you mean by category of E stop Spoon, like i said, new to this area, but i decided after writing the SOP for the process and scrutinising it, although i dont necessarily feel E stops are essential, if i am honest i weanted to put them in because i never have before and wanted to give it a go and couldn't see the harm in doing so, but i opted for standard, latching, twist reset E stops.

Again, I can only apologise that my threads may wind the veterans amongst you lot up no end, but i have no where else to turn for help on these matters than this forum quite honestly, and although thats a rather scary prospect and 95% of you guys wil have just sighed in desperation, i still feel that by coming here and asking my stupid questions, at least its better than not asking, not knowing what i am doing, and just doing it wrong..... wronger....

I am not a total plank, i promise, im quite competent, but there are many many things for me to learn, i am just trying to do that, albeit a little unorthodox.

 

[vaughant]

Yea and i appreciate it fella for sure.

Not really sure what you mean by category of E stop Spoon, like i said, new to this area, but i decided after writing the SOP for the process and scrutinising it, although i dont necessarily feel E stops are essential, if i am honest i weanted to put them in because i never have before and wanted to give it a go and couldn't see the harm in doing so, but i opted for standard, latching, twist reset E stops.

Again, I can only apologise that my threads may wind the veterans amongst you lot up no end, but i have no where else to turn for help on these matters than this forum quite honestly, and although thats a rather scary prospect and 95% of you guys wil have just sighed in desperation, i still feel that by coming here and asking my stupid questions, at least its better than not asking, not knowing what i am doing, and just doing it wrong..... wronger....

I am not a total plank, i promise, im quite competent, but there are many many things for me to learn, i am just trying to do that, albeit a little unorthodox.

Nothing wrong with asking fella but you will always receive some aghast replies as really in a control style apprenticeship like I (and no doubt many others in this section) did,the first thing you learn about any machine is how to stop it and then how to start it.
The safety circuit is always the first part of pretty much any control design because the idea being when you hit the "big red button" you cut everything off as you don't know in that split second whether there's a jammed hand,split hydraulic hose under pressure,burning motor etc,you just know you want the whole machine to stop there and then hence the importance of it and in all honesty it's good to see your trying to incorporate that into your work,but be aware there's a LOT to the safety side of it and there's some really clever bits of kit out there which make it safer for the operator which is what it's all about really.
In ford even the majority of bolted guards had limit switches on them directly linked to some sort of safety device as someone got crushed in another plant by opening a fixed door while the machine was running.
No safety system is 100% foolproof,but it's designed to make you think about why your bypassing it,which often you have to in a controlled environment,rather than just jumping in head first.
I think it's a bit like when the more installation biased sparks get very wound up when folk don't use the correct size earthing etc,I've found in most industries where I've worked it's a case of "use what we've got" rather than always using the exact for the job,often it tends to be larger than required but this is not always the case.

 

[Spoon]

Not really sure what you mean by category of E stop Spoon,

Have a read of this.
View attachment Risk_Assessment.pdf

 

[wade88]

Thanks guys. Spoon, thats great, i have printed that off and bound it into my H&S folder, i am attending a NEBOSH International Cert course next month, so that will definitely give me a good leg up on all of this.

The risk assessments i carry out are based around the guidance provided and templates available online at HSE: Information about health and safety at work as thats been my only point of reference since doing this job.

Good news it however, i just tested the circuit, and it all works fine. Start/stop, the main E stop, forward reverse and all my E stops on the hopper all work. So im pretty pleased with that.

Vaughant you are absolutely right on all accounts, i have no insisted at work here to have almost free rein on my own purchasing accounts so i buy what i want when i need/want it, to allow me to purchase the correct stuff for the job, as spoon has pointed out however and a few others, what i feel is right for the job, may be and often probably isnt, but what i have got this time is working, and it is all safe.


In time and as a gather more experience, i will pick these things up along the way i guess.

Thanks again everyone

 

[KAS1]

I remember when people would employee a design engineer to do the electrical design work (if the inexperienced trainee / electrician wasn't up to it) and then install the electrical installation to a spec lol

 

[KAS1]

If things go wrong on an install it's no good saying to a paying customer "well that's what I was told on a forum" does your customer know you're getting most of your information on here? even how to make a good job of traywork lol

- - - Updated - - -

If things go wrong on an install it's no good saying to a paying customer "well that's what I was told on a forum" does your customer know you're getting most of your information on here? even how to make a good job of traywork lol

- - - Updated - - -

don't know why that posted twice

 

[wade88]

It's not for a customer, it's an install at the company i work for. Im the plant manager here, but do all the maintenance, electrical and plumbing work. Well i do everything really.

Yes the tray work isn't brilliant, im totally over that, it's not affecting the operation of the circuit, ill get it looking nicer next time, and no i fully understand it's not ideal getting tips from a forum, but i'm not entirely sure what else i should do. For topics i am unsure about, i seek help where available, and, for all intents and purposes, i have now installed a safe and operational circuit after some guidance. I'm happy.

 

[KAS1]

sorry Wade I was getting misled by your link to a website I thought you were an electrical contracting company, my mistake, my advice would be if they've employed you as a plant manager why don't you contract the electrical work out to a qualified electrician? and then manage the contractors?

 

[wade88]

That (was) my company, don't work self employed anymore, but as the websites suggests i only did domestic jobs and event power, now i have moved into a more industrial environment by proxy i guess.

Yes some work is contracted out, so typically as a plant manager i would be managing the tasks to be completed by outside contractors, but because im fairly handy, i started to do everything my self, and then i ended up falling into the control side of things, of which i know very little. Everything else i am totally happy with, but since having been involved in PLC's and the actually operation of heavy machinery and their panels, i have for sure lost my way a little.

I am however, picking it up quite fast, and rest assured, and i am being more sincere, any jobs i seriously don't feel comfortable with, i simply get people in, that goes for everything else i do outside of electrics. But, electrics kill people, a badly soldered yorkshire joint on a soak away will just get someone wet, so i fully respect the difference and always have.

I think people here think i just dive head first into serious work with no idea what im doing...... *cough* ........ but i do honestly do as much research and reading and general background as i possibly can before i even get the tools out.

I do need to remove that link now you mention it.... not that its even done me any good lol! But i am just a humble plant manager now.

 

[Knobhead]

All I can say Ben, it must be a laid back plant to manage. Been there got the tee shirt and made the maintenance guys life a misery. I hadn't got time to go delving in to things. I'd got 50 guys to keep employed in some way or another. Fix that bloody plant NOW! or I'd have you shot at dawn!

 

[Darkwood]

Hmmm... i applaud your enthusiam wade but even with the advice give and links the risk assessment and safety side of a control system isn't something you can work out, learn or be competent to do in a short space of time, there are so many indepth requirements as well as positioning segregation and design of the control system that couldn't have possibly even been touched on here in such a short thread up to press.

Ive briskly wisked through the posts and il stand corrected but i see no mention of seperate reset in that resetting of the E-stop will not on it own re-energise the disabled circuit or control circuit as a seperate manual reset will be required to be operated to be able to start the the dropped out circuits.

I can recommend you pop into your local Engineering wholesalers and pick up the free booklets from the likes of Pilz, Schneider or rockwell....i have the rockwell catalogue on their control safety products and is a wealth of info although biased with their products as solutions it gives an indepth read-up on how to risk assess to find what safety catagory the machine falls under , relevant EN an IEC standards, examples of safety set-ups with wiring diagrams for each catagory and all the formulas for designing more advanced systems where distance to hazards need calculating in relation to safety detection circuits.

I know you won't take offense when i say you really shouldn't be entertaining designing your own E-stop systems with the help of a forum as too many questions and answers to ask and know about the machine and job and user interaction that could be possibly asked .

Tred carefully as no PL-insurance will cover you for this unless you have specified it within your duties to design and alter or build control systems, if you or your company has this clause covered in insurance you will probably still lose cover if it dosn't comply to EU Directives and regulations. If the worst case happened without such cover it could bring your company down.

 

[Knobhead]

Not worth the effort DW.

 

[majaya]

Have you checked your cables to earth? You might be having an earth fault or damaged cables.
Whats the source of your 24V?

 

[Darkwood]

^^^^^^^????????

 

[wade88]

Ok, aside from Tony's useful input and don't feel you need to come back with anymore helpful nuggets of wisdom here old boy im sure you have plenty of other people to go and wittle away at.

Aside from college, as i just can't go down that road for an array of reasons anymore, where and how is the best way to read up on the "regs" of such topics such as control circuits, industrial control and the like. Are there courses available that are recognised, and what is the best way to learn more. I have a lot of reading to do which some kind forum members have sent my way, and i am attending a NEBOSH course in a month as i will be taking over the SHE managers job role in the forthcoming weeks also.

Yes it is a small company, and yes for the last ten years it has been a self sufficient entity with no outside involvement in regards to maintenance and everything else. Repairs and new builds of gear have taken place in a very Heath Robinson manner but i was asked to come in and take over that aspect of things as well as over see the design and build of any new engineering projects we are undertaking.

I undoubtedly don't hold the experience many of you do, and undoubtedly have not "commanded" as many men as some of you either, led the charge through the breach at the Tea room 2 minutes before break time, or even shouted at a poor maintenance tech till he cried and curled up in the fetal position, but i have just started this career no more than two years ago, and have not had my hand held through the beginning of it so have done my very best to work things out for myself and do what i feel is best. I do my upmost to keep safety as a priority and yes, as pointed out, sometimes get it wrong or have done things in somewhat of an unorthodox fashion, so i come here to get a little steering in the right direction, not to highlight my incompetence for the pleasure of the vultures here who love to take people apart for a good ego massage.

This forum has fast become more of an executioners social club, where people wait for "silly" questions just to run in swords drawn and hack the poor bugger to pieces. But in my opinion, better a stupid question asked and a person leaves understanding, then no question asked at all. So i fully intend to just keep on asking.

For those of you who deem me to not be worth the effort, thanks for coming this far but by all means do one. But for everyone else who has personally gone out of their way to help me, i appreciate it very much.

 

[SheffSimon]

Google EN ISO 13849-1, thats one of the relevant standards.

Safety - Principles, Standards and Implementation

for a starter

 

[wade88]

That's brilliant, thank you Simon

 

[SheffSimon]

That's brilliant, thank you Simon

No problem, I had a brief look through it myself and its a really good resource, with a lot of good clear explanations.

 

[wade88]

it's just what i need. Top stuff thanks pal

 

[FrankUK]

Found some good information on here LPC Siemens Micromaster440

 

[Brightspark2]

Why not collage?...at night?...distance learning?...

You could get someone to design these things then you install it. Work to there spec.

You just need to be covering your --- wade. If anything went wrong you'd be left high and dry. You'd be responsible for the whole thing with no defense. As you know competence is prooved with qualifications. If your company wants you to do this kind of work then get them to pay for your training.

Otherwise tell them you cant do it and explain nicely why, that it's out of your scope. Look after number one squire because there only be you there if the poop hits the fan.:thumbup:

 

[rmc86uk]

Otherwise tell them you cant do it and explain nicely why, that it's out of your scope. Look after number one squire because there only be you there if the poop hits the fan.:thumbup:

He's the plant manager so they probably assumed he knows what he's doing!

 

[Silly Sausage]

He's also got a high level Law related degree, so I think, our Mr Wade might not be as naive as you all think!

 

[silva.foxx]

He's also got a high level Law related degree, so I think, our Mr Wade might not be as naive as you all think!

Uni...

I know quite a few people who passed thru our Unis with good grades and irrelevant job prospects!

J... sports science degree... now soldering encoders
D... biology + psychology... now safety health & environment
S... sociology + maths... now safety health & environment
A... mechatronics... now portrait photographer
P... geography + history... now sound engineer

Uni... proves you can read books and party with a mortar-board!

 

[Silly Sausage]

Uni...

I know quite a few people who passed thru our Unis with good grades and irrelevant job prospects!

J... sports science degree... now soldering encoders
D... biology + psychology... now safety health & environment
S... sociology + maths... now safety health & environment
A... mechatronics... now portrait photographer
P... geography + history... now sound engineer

Uni... proves you can read books and party with a mortar-board!

Well, I'm glad I went then!, judging by the average posts you get on internet forums... :smilielol5:

Graduating in a subject never meant you'd follow that path, it's an indication of ones intellectual ability.
You're above examples are either cases of they couldn't get the career they wanted or it's an alternative path they have chosen to tread. Remember, since Blair's 50% degree policy, most are probably not worth the paper they're printed on!

At least we can think for ourselves most of the time........




Oh yes, and how did we party at the tax payers expense!!!!! hahahahahahaha