Stepper Driver Help needed please

Hello all,

I have been working on a CNC conversion for my Bridgeport Mill. The original idea was to just motorise the X axis and a 6” dia HV table so that the machine could cut gears whilst I got on with more mundane tasks.

The rotary table was done first with a NEMA 23 motor from Arc Euro and a cheap single axis TB6560 driver. BTW, I have found this driver absolutely fine for the NEMA 23 motor, despite hearing and reading many things to the contrary.

The X axis was the next to be undertaken using a Nema 42 motor and a DM2722A driver from Longs motors, again based in China. This was completed successfully and runs very well when driven with Mach3. For the gear cutting, I can live with the backlash on the X axis, but there are hopefully some ball-screws being brought into the UK for me next month.

Work has progressed on the Y axis conversion and I was all set last Friday to run both axis at once and cut a circle, albeit in fresh air. Unfortunately, the Y axis driver has shown an alarm from initial power up and refuses to work. I swapped the drivers over so that the “older” driver drove the Y axis and the motor was fine.

I have contacted the suppliers in China and they pretty much say that I must return the driver to them for testing, despite all my explanations and photos. I feel that they have me over a barrel really and the cost of posting to China and accompanying delays, doesn’t help my situation.

Is it going to be a practical proposition to have this driver repaired and is there anyone on this forum that could undertake such a task? I feel so frustrated because I came so close, even though I can still cut the gears ok.

Best regards,

Steve.

Edited By Steamer1915 on 27/10/2014 20:15:23

Edited By Steamer1915 on 27/10/2014 20:17:42

Hi Steve,
I've just had a look on the web for a schematic of your stepper driver but I could not find one. Without some information on the device it is nor possible to say weather it would be possible to diagnose the fault. Do you have a picture of the circuit board with enough detail to read the component part numbers ? If you do then there is some chance that one of us on the forum may be able to work out if the components that are likely to have failed are obtainable.

Les.

Thanks Les,

I'll try to take some photos tomorrow but I don't know how good they will be.

Steve.

Hi All

For those interested in CNC

A mate and I are working on a design... He is the electronics wiz
He got a couple of these small PWM stepper drivers using the Toshiba chip.
Pretty good value for money and free Del.

**LINK**

Initial testing one found it OK.,
I have absolutely no connection to the company.

Regards
John

Hi John,
The device that Steve is having problems with is a much higher power device than the two you link to.

Steve,
I misread your post originally. I thought it was the original driver that failed. As it was the new one that was DOA then the supplier should cover the cost of the return postage. If you bought it on Ebay then open a dispute. (Provided not too much time has elapsed since your order.
One other point, As these drivers run directly from the mains it is possible that the wiring to the stepper motors is at mains potential so be careful not to touch the stepper motor wiring when they are powered up. I have this suspicion as it does not give an output voltage (Only the current.) in the specification

Les.

Edited By Les Jones 1 on 28/10/2014 08:27:14

Hello Les,

These are the terms that were placed on the eBay listing. "Returns: 14 days refund. Buyer pays return postage". Not sure how this relates to a faulty component but I think I'm on a bit of a sticky wicket anyway, as this was purchased 2nd September. I have only just got around to fitting it. In hindsight, I should have tried it when it first arrived.

I'm not sure that the output would be at mains potential. The motor is rated at 5.86V DC. I've been running the driver at 110V ac from a site transformer. I made this decision because the 220 volt limit made me think that UK mains voltage might be slightly too much.

Steve.

Hi Steve,
The rated voltage of the motor will be the voltage that gives the rated current due to the resistance of the windings. When the voltage is first applied the current is not just limited by the coil resistance it is limited by the inductance. To step at higher rates a higher voltage needs to be applied so that the current rises quickly. Stepper drivers control the current through the windings so if you look at the voltage waveform across a winding you will see a high voltage at first which will decay to the voltage value that is produced by the set amount of current across the resistance of the windings. I think running the drivers from the 110 volt transformer is a good one for the reason you stated and also it makes it safer because of the lower voltage and the fact that the transformer output will probably be floating or earthed at the centre point.

Les.

Steve;

Not that it helps, but I required 4 drivers for my latest CNC mill, so I purchased 5 from China.

That gives me a spare, and, 5 from China were less than 4 "name badged" ones from the USA (south of me, so there is the border charges as part of the shipping); it's a gamble that all 5 are ok.

As it turns out, the 4 randomly chosen from the box of 5 are all ok, so I do have a spare in case of difficulties further down the line.

John.