Denford Software & Machines

the problem you have is that it appears that the analog side is floating at half mains voltage , this is common with a lot of the older type speed controllers , so you need to isolate the control side and your PC Interface , this can be problematic to solve but ... .

take a look at http://www.homanndesigns.com
the digispeed DC-03 should do what you want and will interface with Mach3 without problems , i'd also go with the dc supply option .

that should get you on your way quickly


Dave

It's already isolated on the CNC4pc board - that's why it specifies using a separate 12v supply for the spindle ref. It cannot share an earth with any of the existing supplies - so it might be as well to buy a specific 12v supply just for this!

The '0v' line on the power supply will float at ~120v with respect to any of the other earths - so it will give you a shock. The 12v line will float at ~132v - so both need to be suitably insulated!

Si

Thanks for the replys, I had a look at the board you recomened basher, and read the manual tiwce, and from what little I know about electronics, could not see what difference this was offering from my cnc4pc board as both offer optoisolation.

Today I connected up a 9v battery to a 10 turn wiper resistor and switched on spindle and had full control of spindle speed. So next I tried connecting 0 to 10v from BOB which it did not like, flames from reverse relay again. The power for the 0v-10v on the BOB is from an old pc PSU which is powered from the machine cabinet 240v supply. I've now blown the fuse in the spindle drive unit, hopefully that's all. Again any further help on this matter would be gratefully received.

Regards Dale

Hi Dale

the problem is the power supply you are using , or the way you have it connected , as stated it needs to be a totaly isolated and independant supply and not common to either the BOB or the Machine , as the 0v or Gnd of the power supply you are using is in effect at Half mains voltage
or there about , so can not have it's output grounded at 0v potential , or connected to a ground tag etc , it needs to be able to float so 0v becomes say 115v then you have your +10v above that

the interface i described has it's own dc - dc convertor so is not grounded
so solves this problem , the cnc4pc cannot cope with any non isolated speed controller because of this .

it's the fact that your power supply is grounded which is blowing your fuses , you are effectively connecting the mains directly to ground so introducing a short

hope this helps explain your problem
in a more understanding way

Dave

Hi basher, I've uploaded Wiring of my BOB.

ok Dale i think the problem is the fact your using a pc power suppy for the 12v , ( presume your using the ground from the power supply to the same gnd terminal next to the 12v of course and no where else )
another problem is pc supplys are switch mode so by virtue of they way they work they are not totaly isolated from the mains

so you will find that a pc power supply does not have a floating gnd they usualy tie it to the case as earth in some cases .

you need a straight forward standard el cheapo transformer power supply , bridge and a smoothing cap giving you 12v , a 12v wall wart type will even do , or vist Maplins etc
just make sure the connections are to that 12v block both gnd & 12v
and no where else and you should be fine ,

the fact that it works if you use a battery is proving the point that it's the power supply grounding the half mains voltage

iv'e just looked at the bob board you have and it should do the trick
apart from the notice warning over a seperate isolated power supply must be used , hence your problem

Dave

Thanks Basher, I'll see if I have one knocking around the shed if not I'll buy. once again thanks for your help.

Regards Dale

I agree with Dave! (for what little it's worth!)

Si

Hi, I've replaced the fuse in the controller which was a massive 20amp with a 5 amp fuse and controller is still working. I've found a 12v old brick type charger and please correct me if I'm wrong, I need to supply 0-12v without a reference to earth like the battery I used. I checked the brick type power supply with my multi meter with one lead on a good earth ( machine cabinet ) and the other to the + and - end of the power supply and I'm getting -0.1v which is jumping around a bit between 0.05v/0.15v when I did the same test with the old computer PSU it was reading the full 12v which basher figured out was my problem. Is this small -0.1v okay?

yea should be fine Dale

let me know how you get on

Dave

Hi Dale - love your "green" re-use of old hardware, but wondered whether a phone charger was capable of 2Amps ? - was it one of those huge "mobiles" from the 80's

Spindle now running under full control of Mach. Thanks to everyone and to basher for your help pin pointing the problem. I've upload modified jpeg of BOB wiring just to help anyone following the thread. Next job is to tidy all my cables into the machine cabinet. Next on my list is to buy a license for Mach, then I'll upload some video on youtube showing off my new axis speeds. Only two jobs left, limits and homing switches, and tool release from spindle. Which I plan just operating from a switch manually placed somewhere inside the machine. I'll take a wee breaking for now, as the last three or four weeks have been all about this machine.

P.S. LOL basher, I do like to re use as much as I can. I've got a good few brick power supplies from over the years of various gadgets packing up. I'll plug a good website http://www.freecycle.org/ I just got two 15" monitors which are perfect size for the triac. Don't no what that 2amp brick was off.

Regards Dale

Just an update of where I'm up to on my conversion, I've uploaded some photos on the separation of the mill from the machine cabinet. I've done this to save space. Next on the to do list is weld up a small table to house the mill, electrical cabinet, computer and monitor. I've removed the tool changer as this will be done manually for now, but I am undecided on whether I'm going to use air draw bar or make a manual lever.

Hi, another update and a request for help. I've uploaded a pic of the mill free from the old machine cabinet and a reduced work bench. I am very happy with the space I have saved . I have also got the tool draw bar to work from a switch which I have mounted under the machine cabinet, and have incorporated a small safety feature using a 24vdc relay to disable outputs on BOB when draw bar is active (see photo).

My request for help is on the matter regarding the datum sensors, I have managed to trace the cables from the wiring diagram (see photo) and have done a resistance test on x axis sensor, all is fine. The diagram indicates 12v @ cable 65 going to the sensor and returning via cable 66, the problem is that there is no voltage at cable 65. So next I added 9v supply from another old mobile phone type charger and placed a piece of metal in front of the sensor and noticed a 0.5v increase. Does anybody no a way of wiring and configuring this type of sensor to Mach's 5v I/O?

I am planning of leaving the mechanical limit switch's as they are. As when they are switched power is cut to all drives, Mach will still carry on running through the program, but the machine will be in a safe state. Any information would be gratefully received

Regards Dale

If I've understood your question....
If you've still got 12V in there, then drive a 12v relay from the sensor (thats what we've done when we mess up and get the wrong type (PNP or NPN) and need to change the inputs normal state.
This relay can switch the Mach input to gnd (or +5v - whichever?)

Hi,
Its finished.

I've made a few test pieces and the machine is running great.
I replaced all the datum switches with micro switches, it was a little tricky as space was tight, but it made for simple wiring as I used the 5v from the output on the BOB and picked up the wiring from the 50 way interface RS board in the machine cabinet. I'll take some video and post to youtube in the near future. Thanks for everybody's help with this conversion

Regards Dale.

Well here are two videos of my finished conversion to Mach using original hardware. This one http://www.youtube.com/watch?v=nM7UC2k_ ... re=channel is about the electrical side of the conversion which I have given a very basic out line of the steps under taken. The second http://www.youtube.com/watch?v=uVbVqZ6R ... re=channel is me moving the axis and performing a surfacing and engraving cycle using the free wizards that come with Mach. Now I am learning how to use Mastercam so I can machine in 3D. I 'll upload a video when I get that far ( it will be a while yet ) . If I can be of any help to anyone trying a similar conversion feel free to PM me. Thanks for all the help I received, without it, this conversion using the original hardware would not have been possible.

Here are some bits left over from my conversion if anyone whats them I'll ship them just to cover the cost of posting and packing, paypal prefered. If you have read this thread you will understand these parts have been removed from a denford with noise problems so I can not guarantee if there are fully working. They might just keep an old machine going for a bit longer.

Regards dale

Hi Dale

I am interested in the EPROM and the two cards. (Mint & Costum Card)
Does your offer still stand?

Best wishes

Enny

Hi, mint chip and controller cards have now gone, I've uploaded some new videos of thread milling and edge finder.

http://www.youtube.com/watch?v=TUaNEgoKgKw

http://www.youtube.com/watch?v=wkJUUT657L8

Regards

Dale