Help with Triac VMC converting to Mach

[Dale Gribble]

Hello,

My Triac control died last week, so now I'm looking to covert to running on mach, piggy back style. I have tried to follow previous threads on the subject but I am struggling with the basics. Electrics are not my strong point. I have taken a photo of my electrical cabinet. The first question I have is where exactly do you tie in the step and direction signals.

I have tried to trace this but only got as far as the back of the motherboard where the signal go's into the eurostep controller. I have removed one of the driver cards, and using a multi meter placed one probe in 28c and using continuity test tried to trace it to the std 50 way interface but am getting no signal. I do have the power switched on. Does it matter what the LED is displaying currently L.
Any help on this matter would be gratefully received.

Kind regards Dale

P.S. If and when I get this running on Mach I'll post the whole process in one thread with photo's maybe even a video or two.

[SimonRafferty]

From what I've read on here - and what I'm in the process of doing - the two simplest options are:

1: Ignore the controller altogether, apart perhaps from the power supply. Buy a breakout board (cnc4pc) plus spindle / stepper drivers (Gecko) and connect it all up. Then you only need to trace the wires from the motors and spindle encoder.

2: Keep the stepper and spindle drives and use a breakout board (cnc4pc) with an analogue (0 to 10v) output to control the spindle inverter.

Inside your machine, there is probably a pair of connectors (on my EasiTurn there are a 26 way dual in line plug and a 10 way single in line molex header, both available from Rapid Electronics).

Interrupt (by unplugging) the leads where they plug in to your control board and plug them in to sockets wired to the breakout board.

On mine, the 26 way carries X & Z step + direction, enable, coolant, chuck, toolchange and a 24v line. The 10 way carries all the limit and home switches.

I'm going to strip out the old CPU, keyboard and interface boards and replace the interface board with the breakout. Mount a TFT monitor on a new front panel with a pair of rotary encoders for X & Z traverse.

This keeps all the stuff like the lube pump, low volt light and the big red stop button original and minimises the butchery required!

Si

[Dale Gribble]

Thanks Simon for your reply

The reason I bought the mill was to help with my build of a cnc router to make all the motor/spindle mounts. I have already built the electric's for this project. I do plan to do a total re- fit for the triac with new driver cards, but that's way in the future. To save time and money I am looking to convert to Mach using the current hardware.

I've had a look at That breakout board from cnc4pc looks just the ticket.

I just received my order from Maplin of the resistor's and transistor's (see Jpeg I've upload ) I'm going to have a go at making some kind of board to tie in directly onto the motherboard. I will post my success or failure's on how I get on.

Regards

Dale Gribble

[comet]

Dale,
I am looking to do what you are doing on a friends machine.
How have you got on with it?
succesfull?

[SimonRafferty]

Last night - I had the drives operating under Mach with the CNC4PC board.

Although I'm converting a Lathe - the principle is the same for a Mill.

I have to wait for some more connectors to arrive tomorrow for the spindle, home, coolant.

The home sensors are inductive and require another simple circuit to interface to the BOB.

When I have satisfied myself that it all works OK - I'll do a complete write up with circuits etc.

Si

[Dale Gribble]

Hi Comet

I've soldered up the transistors and have checked with a multimeter what is going on with this circuit. I've put 5v in and I'm getting out just a wee bit less 4.9v I am not sure what really going on with this circuit. I'll hook it up to my z axis and give it ago this weekend and post my results.

Hi Simon

Good to hear your progress with Mach. Looking forward to your write up of what exactly you have done.

Regards

Dale

[Roy]

Hi, I am looking to convert my Triac to mach 3 using the existing hardware as you have. Which breakout board are you using from CNC4PC? Is it C11 ?

Thanks Roy

[Dale Gribble]

Just an update of where I'm up to so far. I've soldered two cables onto the back of the motherboard see photo's 2 and 3. On photo 2 I've removed z axis driver card. you can tie the step and direction by using the two small holes below the numbers 30 / 32. This can be repeated for the other axis.

I then powered up my machine and using a 5vdc power supply touched on pin2 on my 25D connector the motor pulsed one step then I added 5vdc to both pins motor moved in reverse. I keep on playing around and in the end nothing was happening.( I maybe have fried the transistors) I got the motor moving again by touching 5vdc directly to the cable's I soldered onto the motherboard. I've just ordered a C11 board from cnc4pc. I did not connect it to my pc and test with Mach, I'll wait for the new breakout board as this is opto isolated.

[Dale Gribble]

Just an update on where I'm on with the conversion, I've uploaded some new photo's. I've soldered step and dir cable's on to the back of the motherboard which are connected to the homemade voltage amplifier circuit, which is then connected to the BOB. Well how did I get on, The first time I switched on the motors they were jumping around and slowly creeping. Turned off and on machine control and this time motors quiet and no jumping or creeping. I tried to move the motors under mach I got nothing on x and y but I did get movement on z but only in the minus direction. I couldn't tune the motors, no matter what setting I tried the motor only turned slowly.

I have asked on yahoo answers about the voltage amplifier circuit and they have replied quoting that the circuit is too simple and would not amplify 5v up to 12v. I think this is my sticking point if anyone can help with this issue I would be grateful.

[Roy]

Hi Dale,

The drive board should work ok, providing you have it wired correctly. Mine works great on my triac with digiplan drives and the same breakout board as you.

Just looking at your board (you may have it correct but i can't see it well enough). The ground pin on the transistor should be the right hand one if looking at the transistors flat face.

To get my steppers to run smooth I had the dir active low and step active low turnt off, and motor tuning with 200 steps.

Cheers Roy

[cncbasher]

to move using the step and direction pins , u need to pulse the step pin each pulse of 5v will step the motor one step , so holding the 5v will not make the motor rotate continously , just quickly touch it on and off will do the trick . you will see the the motor sort of jerk in whatever direction is set via the direction pin . you'l hear the motor rather than see if move as each step is very small , and unless you can pulse the pin very fast you will just see the move . at least this will check your circuits

the direction pin needs to be held to 5v or 0v to select direction this can be held to 5v or 0v all the time and not pulsed , this will give you your forward or reverse

[SimonRafferty]

I think before you go any further, you need to find out what is actually happening!

Disconnect your transistor drivers from one step and direction input. Then measure the voltage between the step input pin and ground, and again for the direction (with the stepper driver powered up).

It should read somewhere between 6v and 12v - so long as it doesn't read 0v - then the above circuit should work.

Since you mentioned that the motors are 'jumping around, it means that noise is activating the step and direction inputs. To me, that would indicate that the input is 'floating' - not connected specifically to 12v or 0v - but allowed to float in the middle somewhere.

If it sits at less than 6v, it needs to be pulled up closer to 12v. To do this, connect a resistor (the value of which doesn't matter too much - somewhere between 1k and 3.3k will probably be OK) between the input and 12v (the 12v must come from the stepper driver PSU, not the BOB).

Measure the voltage again - and it should be on the right side of 6v (between 6v and 12v).

The transistor amplifier described above 'pulls down' the input to somewhere close to 0v - and can only work if there is something else pulling it up to 12v the rest of the time - hence the resistor.

With the resistor connected, your noise problem should vanish and the motor should step when the input is touched on the 0v line.

Next, without the BOB output connected, try touching the input of the step transistor amplifier (the 3.3k resistor) on one of the 5v BOB connections. It should step the motor. If it does not, check your wiring. It may be that you've blown the transistor (or connected it up wrongly).

Next set one of the BOB outputs high (a dir output is easiest as it will stay high or low when you change direction). Test it with a meter to make sure it is sitting at between 3 and 5v.

Try touching the step input on the transistor amp to this line. likewise, the motor should step (judder). If it does not, it may be that it does not spit out enough current to drive the transistor through the 3.3k resistor. You may need to reduce the value of the 3.3k resistor a little.

I found mine was most happy at between 1k and 2.2k - bit of trial and error here!

In summary, go through the whole interface one thing at a time. At the point it appears not to work - there is your problem.

Let us know how you get on and I'll try to be more specific about what might help!

Si

[Dale Gribble]

Thanks for everybody's reply. Roy I do have the ground pin as you pointed out thanks. Simon I disconnected transistor circuit form BOB and measured voltage on all drives both step and dir and the reading range from 11.5 to 12v. I've then connect up x axis to BOB, motor is quite when dir is active high but when I change dir 0v motor is noisy and stays nosey until I change dir active high again. I've checked the volts coming from the BOB( transistor circuit disconnected from BOB ) dir = 0v-5v but step is only outputting 0v-1.25v. When I check then volts @ the collector end of transistor on dir I'm getting 8.8v when mach is outputting 5v and when mach outputting 0v I'm getting 11.7v. On step @ collector end when mach outputting step and dir signal =9.7v and if only outputting step volts = 11.1v. I've uploaded a wiring diagram of the transistor circuit I've made to see if it's correct. Is this transistor circuit acting as a switch to alter 12v to 0v from motherboard when receiving 5v from BOB? Hope this information can help with tracing my problems

[cncbasher]

Dale
give me a ring or call on skype if you have it etc , and i'll see if we can work through your problem

i think you may also need a pull up or pull down resistor from the base of the transistors to +5v or down to 0v depending on the logic of the ttl input

the transistors may not be fully switching

regards
Dave

[SimonRafferty]

The transistor is obviously not turning fully on.

It's strange that your step & dir outputs are showing different voltages!

Is it possible that the step output is pulsing (switching on and off v.fast)? On mach, try swapping the step & dir outputs and see if the voltages shown reverse as well.

A transistor behaves a bit like a dimmer switch on a ceiling light where the knob it 'turned' by the current flowing from the base connection to ground.
The virtual ceiling light is connected between 12v and the collector.

With your setup, the dimmer is only being turned 1/3 of the way round - and the 'light' is not bright enough to operate.

Transistors have an associated gain - which means that the amount the 'knob' is turned for a given current flowing between the base and emitter. differs from one type of transistor to another.

I suspect that the transistors you are using do not have enough gain to pull down the step & dir inputs close enough to 0v to operate correctly.

I would try changing the 3k resistor for a lower value. That will allow more current to flow from the base to emitter - which in turn allows more current to flow between the collector and emitter.

Try 2.2k then 1k.

The transistors you are using are BC547C which quote a gain of 420

This means that, with a 3.3k resistor, it should allow 600mA to flow from the collector to emitter - which ought to be plenty.

Try connecting your meter, set to mA between one of the step inputs and 0v - this will give an indication of how much current needs to flow through the transistor to operate the board.

Let us know the result.

Si

[Dale Gribble]

Hi guys, thanks for your continuing input. I have uploaded a new photo of the alterations to my circuit board I added two wiper resistors to find the best resistance, I adjusted to 2k to start with, I switched on machine not much difference adjusted down to 1k and x axis moved in one direction but I also noticed z axis was moving at the same time but the z cables were not connected to the BOB. So I connected the z axis cables to the BOB and I got movement in both directions on z axis ( movement is slow and does not responded to motor tuning) I then moved the earth from the emitter on the transistor circuit from BOB pin 15 to machine cabinet and I got movement on x axis in both directions. I'll upload a photo of the back of my transistor circuit which shows how I connected all the emitter side of the transistor together which I connected to pin 15 on BOB but then I moved it to the machine cabinet. Is this incorrect? ( I tried moving emitter side of the transistor to different earths which did have an inpact on noise )

[SimonRafferty]

Well done!

Sorry - should have said that the BOB, Transistor and Stepper driver all need to share a ground.

Si

[Dale Gribble]

Bingo!!!

After a stressful three weeks the Motors are zipping along except y but I think thats just a bad connection on my transistor board. Only had a small amount of time to play with the tuning. I've doubled the z speed to 2000mm/m and x is running @ 2500mm/m. Big thanks to simon and everybody else who contributed.

I'll now tidy up my cables/circuit and upload the photo's in the near future.

[SimonRafferty]

Well none Dale! It's a good feeling isn't it!

Si

[Dale Gribble]

Just an update of where I'm up to. Fixed Y axis by replacing a transistor. All axis are now running well Z axis 2000mm/m, X axis 2750mm/m and Y axis 2500mm/m with acceleration greatly improved. Next I worked on the spindle, using one of the onboard relays on my BOB I bridged cables 53 and 52 ( take care as I did get a shock I think it's 30vac ) and removed SGR see photo. I then enabled spindle in Mach, typed in M3 in MDI mode spindle switched on and even rotated at around 30rpm, so far so good. Next I re-used the power supply of the old pc to supply 12v to the 0-10v analogue output. I followed the set-up from cnc4pc BOB which supply setting for mach unfortunately this did not work. Basically I spent half the day try various setting altering steps and velocity in motor tuning and PWM in spindle configuration and adjusting the wiper resistor on the BOB and not forgetting step pulse on motor tuning. I was struggling to get the ratios right e.g. 10% of spindle speed = 1v and 20% =2v etc. Anyway here's my setting, in motor tuning, step 600/ Velocity 2500 /step pulse 5 and in spindle configuration PWM 3000. Next I thought I'd try and connect the 0-10v output up to spindle controller which from wiring diagram are cables 54 and 55 (see photos) first I checked volts at these cables no reading, but when I connect multi meter to 54 and cabinet earth spindle ran @ max revs and read 110v so for safety I thought I would connect 5v from the old pc power supply as a test and save my BOB. Good job I did as when I turned power on machine cabinet and no lie there was a big bang and flames from the spindle reverse relay. I turned off the power quickly and removed relay one pin black from fire but I thought I blown the whole controller, but after checking the fuses none were blown and when I plugged relay back in, spindle turned on. So this is where I need help, connecting 0-10v analogue supply to spindle controller. Any information would be gratefully received.

Dale