Ahhhh. Right. Thanks Clive.
So lets say 3 amps from the PSU controlling stepper motors and i think i read 9 max from a VFD.. ?
So does that mean I could potentially run it all off one plug then with a 13a fuse?
Sorry for the dumbness on my behalf. I had to remind myself how a ground / fuse works earlier.
Really getting somewhere now.
So it's decided that I need one power input into my enclosure and split it. Not listening to the bloke that told me I had to run two plugs any more.
So one side of the internal mains split will go to an EMI filter and then to the VFD.
The other side of the split will go directly to the 48V PSU.
One single all in one 10Amp chassis connector / fuse / power switch.
Easy. Job done.
Apart from Emergency stop.
So can anyone confirm why I can't just use an inline mains e-stop button. How does a relay do the job better ?
Thanks massively for your help.
Just been trying to work out who the good people are!
I've had so much conflicting advice, it's hard to tell what's real and what isn't.
Found the answer to that now.
Neale. Thanks. I use those Network plugs to around my house. Will look out for the drop out. Wonder if the EMI filter might stop that.
Last edited by mturneruk; 26-11-2015 at 11:06 PM.
The reason that isn't safe is because the minute you release the E-stop the machine is live again and in some circumstances could just takeoff if the Control software is still out putting pulses.
Also your dealing with Mains voltage levels at the E-stop switch which isn't ideal. Much better to handle control of high voltage with low voltage switch gear.
Proper Safe system should shut down Critical power in safe manner and inform any relavant parties, ie Control software. Then when fault is cleared power should only be restored in a controlled manner IE: With Reset Button that won't allow Reset unless fault is cleared.
The system I've drawn you is the simpliest but Safest E-stop there is without getting daft. It may look complicated but it isn't. It uses only one 4 pole Normally Open relay for the Safety side and one Momentery NO Switch.
On top of this I've included another relay to give you a better Limit switch system to protect against noise. This uses 24V running thru the switches to control turn on Relay that if tripped or wire breaks then cuts Signal from BOB and informs the Control system Limit trip as occured.
This means the 5V Signal wires form the BOB can be kept very short so much better protected from noise than if running all the way around the limit wires acting like an arial. 24V also keeps the contacts of the switches cleaner so less switch bounce.
I've drawn the Fan running on 48V which isn't ideal because they would be turned off with E-stop but thought you already had them so if you haven't got them already then buy 24Vdc fans and run directly from the 24vdc supply.
All this lot, inc VFD will happily run of a 13amp fuse on a single socket.
Now here's my Disclaimer. Use this diagram at your own risk I accept no liabilty if any errors and warn you it's a minimum of safety.
Regards the Fans then you will get dust even with an extractor so fit a filter. Ideally you want 2 fans with filters blowing Air into the case and then vent hot air out. This provides positive pressure and keeps dust out while rapidly removing heat.
Your lack of space makes this even more important so skip this step and you'll shorten life of anything in there.!
Last edited by JAZZCNC; 27-11-2015 at 12:17 AM.
Amazing. Jazz. Digesting. Thanks for your effort!
Listening. Think I might owe you a few beers.
Only problem is I have a feeling I might have to ask you some more questions.
Last edited by mturneruk; 26-11-2015 at 11:30 PM.
For the limit switch circuit Jazz proposes, you should add a diode across the relay coil to suppress the inductive spike, which would otherwise reduce the lifetime of the switches. If you're using them just as limits, not home switches, then that's not the end of the world. Either way I'd be more keen on using a transistor in place of that relay, since it also (for all intense and purposes) removes the small delay caused by the relay contacts moving. Again, not such a big deal for limit switches but it would reduce the accuracy if these are used for homing.
I wouldn't bother fusing the fan - do you really care if it blows up, it's only a fan...
There are many many wise people on here and NONE will deliberately send you wrong.! . . Some tell it better than others. Some say the same thing but go round the houses. Some say it in ways only Nasa trained alians understand.!!! . . . But all say it with helping in mind and good intentions. So when more than a few say the same thing, even if said in differant ways then ignoring what's said is sure fire way to piss folks off and make them look the other way when you really do need there help and only they know the answer.!
I was trying to keep it simple Jon and most Relays come with Diode these days so didn't want to complicate things, esp with Transistors.
Was for Limits only has you know I wouldn't suggest running thru Relay for Homes.
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