Thanks again for your help chaps.
It seems sensible to have the whole system shut down when e-stop is pressed. I would agree that it's a basic safety requirement.
So the next question is how to do that with a relay?
5v transformer in the box sounds sensible. I should be able to get a very small one. This could also possible run the case fans instead of 48v.
I think I understand what your saying about having one plug socket.
I would love to use one socket, but I was told to use 2 plugs by someone else at CNC4YOU so as not overload the wall socket. I thought 13A was the max?
Isn't the VFD using 8amps ish and the steppers / 600w power supply using a load more. E.g. Taking the load over what you can pull from a standard house socket?
EDIT : Can anyone confirm how many amps should be allowed for VFD driving spindle + 600 watt power supply driving stepper motors?
Obviously it's confusing on the forums, cause you have a load of guys talking about 3 phase and it's hard to tell what's what.
I thought I knew what i was doing. Obviously not.
If I have to scrap the case and get / make a bigger one I will (Or i might just take the VFD out into it's own box), but it would be nice to get it all in one.
Last edited by mturneruk; 26-11-2015 at 05:41 PM.
Also have you thought about sucking all the dust into the control box..Clive
Yes. It's not to bad as I have an extractor. Bear in mind this is a hobby machine, it's not going to be running all the time.
I hoover up as i go along as well.
I'm sure Jazz will come back with a wiring diagram shortly....I'm on my mobile whilst cutting stuff on my machine!!! In essence if you get a 24V (DIN rail mounted) PSU (1.5A or there abouts) and take the +ve from it through the E_stops and into a relay (take the -VE to the relay too but direct), when you hit the E-stop button it cuts power to the relay. You wire your mains through the relay contacts (NO) so that when it drops the power to the relay (E-stop) it cuts the power (the contacts open as no power to the relay) to the drivers etc. You can then get 24V fans for your case and supply them from this PSU as well! I suggest 24V as it's pretty noise resistant so good for safety circuits.Neil...
OK.... Thanks Neil.
Do you run your whole system from one physical plug socket or 2 - E.g. One for VFD and one for CNC ?
Why can i not use a 10Amp mains emergency stop button which cuts power in the AC mains line, thus doing away with the relay, transformer and all associated wiring....
e.g. Like this...
I want to keep things simple.
I really like the idea of having one physical kettle lead plug into my box, but I need to understand how many amps a VFD on full chat + 600Watt PSU driving stepper motor drivers will pull.
I have done some more research and a standard household plug socket is 13A max.
One things for sure is I need to check my consumer unit and understand my ring main better. I don't know what ring it's on or what else it's driving. Will do tomorrow.
Last edited by mturneruk; 26-11-2015 at 10:04 PM.
The E-stop through a relay can also send a signal to the software to shut things down. It's really bad for the VFD if you just cut the power in full flow, could damage it.
I've had them all running from the same socket but only for testing, not doing any serious cutting.Neil...
Found some maths.... Not sure if it's right.
I (Amps) = P / V
So for my 48V power supply...
600 Watts / 48V = 12.5 Amps Potential...
Is that right. Something tells me it's more complicated than that..
I read that somewhere to, but what's the difference?
Surely if you cut the power to the VFD with a relay or with a switch your still cutting the power ?
Don't get too wound up about the total consumption via the mains plug. The VFD is rated at 2.2KW. That means that it is capable of delivering 2.2KW, not that it actually takes that power all the time from the supply. The chances are that you will hardly ever, if at all, run the spindle at those kinds of levels. So most of the time the VFD will be drawing much less. Similarly, a 600W PSU is capable of delivering 600W, not that it will draw this all the time. Again, chances are that you will hardly ever be running at these levels. However, worst case, VFD draws 2.2KW, PSU draws 600W, total 2.8KW. For rough estimating purposes at normal mains voltages (and it keeps the numbers easy) assume 4A draw per KW. So, that's 4*2.8 = 11.2A. A 13A plug and socket should be able to deliver this continuously (this is electric kettle/washing machine heater kinds of loads, or 3-bar electric fire). That's why you can run any normal size CNC router off a standard 13A socket. The issue about separate supplies for VFD and the rest of the electronics is that the VFD probably generates the most electrical noise, some of which is fed back into the supply and hence to anything else on the same ring circuit. If you have two sockets in the workshop fed from separate ring mains, then it's best to use those to keep VFD separate from everything else. However, that's very unlikely and if you have a double socket, then both sockets will be on the same ring. So it doesn't matter if you use separate plugs, or single cable into the box and then split it - they are still on the same ring main.
My machine has been running happily like this ever since I built it and I have never had any problems. I use an Ethernet-over-mains adaptor to get a network connection into my workshop (useful for copying files from my main machine where I do CAD/CAM things) and that works well until I switch on the VFD. Then - nothing. That's due to noise injected back into the mains. However, I don't need the network while I am machining, so no problem in practice.
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