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Compact 5 Mach3 conversion
« on: November 30, 2014, 07:19:54 AM »
Hello Folks.

For a few months now I have been modernizing a old EMCO Compact 5 MK1 CNC lathe. I have built a new control system using a kit from CNC4You (Probably not the best parts out there but it will do the job for now). I have also replaced the stepper motors as the originals couldn't pull the skin off a rice pudding.

All that works fine now, so I am on to figuring out how to run the spindle... this is what I cant figure out. The lathe has a 180vDC 3 amp motor. Could anyone on here tell me the method to which to connect this to the BOB and the mains. From reading other posts on this subject, it looks like I need one of these:

http://www.ebay.co.uk/itm/5A-Motor-Speed-Driver-Controller-MACH3-Spindle-Governor-PWM-Speed-Control-AC-DC-/321376265778?pt=UK_BOI_Industrial_Automation_Control_ET&hash=item4ad384a632

But after that I am stuck. How do I connect this to the Mains and to the Breakout board? I am not an electrical person really, so any help and advise people can give me would be great.

Many thanks,

Peter Dawson

Offline DMBGO

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Re: Compact 5 Mach3 conversion
« Reply #1 on: November 30, 2014, 02:50:10 PM »
Yes, you could use one of those. In my case I simply used a solid state relay, and used the existing pulleys to alter the speed. The issue with single phase motors, as the Emco has, is that they lose a lot of oomph when you slow them down.
The SSR is easy to connect, you just connect the 5v output for the spindle from the BOB to the SSR (usually marked 5v), then you break the Active AC wire with the 2 terminals on the SSR marked AC, so that the Active wire to the motor only turns on when the SSR is on. The neutral and earth remain connected to the motor.
Cheers
Dave
Cheers

David

Offline mc

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Re: Compact 5 Mach3 conversion
« Reply #2 on: November 30, 2014, 04:22:17 PM »
Dave, Peter has a DC motor, so your suggestion won't work.

Personally I'd recommend a KBIC, however they're at least 4x the price of the ebay link.
That controller alone would provide you with speed control, however for full cnc control, you'd need to add a relay so power gets turned on/off, along with a step/dir to 0-10V converter which will most likely have to use an isolated supply. And that's only if you want single direction control. If you need to reverse the spindle, you'll need to add another relay into the circuit.

The simple option is the linked controller combined with a relay to turn the spindle on/off, and using a potentiometer to manually set the speed.

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Re: Compact 5 Mach3 conversion
« Reply #3 on: November 30, 2014, 04:29:23 PM »
Sorry about that.
The Emco Compact 5 I converted was for someone else, but it had an AC spindle motor.
Cheers

David
Compact 5 Mach3 conversion
« Reply #4 on: November 30, 2014, 05:41:46 PM »
Peter, that unit is not suitable.  There is another thread here where someone bought one and has been having huge problems, though the eBay listing says it is suitable for Mach 3 the person who designed it clearly doesn't know how Mach 3 works.  A better unit is eBay item no. 181473818094 - other people have commented that they work ok, I have one to drive a similar motor but haven't tried it yet.  KBIC controllers are also very good, I have one on my Novamill.  Watch out for dc motor speed controllers that are not mains isolated at the control input.  There are a couple of threads here on that.


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Re: Compact 5 Mach3 conversion
« Reply #5 on: December 02, 2014, 03:46:11 PM »
Many thanks for the advice chaps! That unit looks good. Im quessing instead of having the switch there I can wire that to the Spindle relay on the BOB?

Do I need to buy a transformer to run this unit? If so any advice on which one to get?

Cheers,

Pete
Compact 5 Mach3 conversion
« Reply #6 on: December 02, 2014, 05:19:36 PM »
I can't recall where the other thread is, I think it's this forum, but someone posting there said you didn't need an isolating transformer, I guess there must be an opto isolator to isolate the control input.


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Offline mc

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Re: Compact 5 Mach3 conversion
« Reply #7 on: December 02, 2014, 05:38:01 PM »
You don't need a transformer, certainly not for the main supply.

The issue is with this style of controller, the control input is at a reasonably high voltage. My hazy memory thinks about 50V, but could be higher, you certainly don't want to be touching the control wiring while power is applied!
When used with a potentiometer, it's not an issue, however when you try connecting it to your non-isolated 0-10V control electronics, you are pretty much guaranteed to fry something, as you short out that high voltage through the control.
The solution is to use an isolated 0-10V supply. Typically the 0-10V output on BOBs I've seen is opto-isolated, and can use an isolated 10+V to provide the full isolation required to control this type of drive. The usual way to get the isolated supply is to use an isolated DC-DC converter, which can be bought for not much money. Something like this - http://www.ebay.co.uk/itm/1PB0512LS-WR-Powerpax-1W-Unregulated-DC-DC-Converter-SIP-Scp-5V-In-12V-Out-/131156823235 will take a 5V source, and provide you with an isolated 12V power source.
Compact 5 Mach3 conversion
« Reply #8 on: December 03, 2014, 04:13:13 PM »
In this thread:

http://www.mycncuk.com/threads/7992-Denford-Novamill-Mach3-conversion/page2?highlight=Novamill

on another forum I'm afraid, I suggested a circuit that didn't need a separate power supply.  I managed to track down the other thread I thought I remembered over on the model engineer site, but I misremembered it, it didn't mention that the control input was isolated.  Mc's point is important, actually the control input may be at mains voltage.

http://www.model-engineer.co.uk/forums/postings.asp?th=100230


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