View Full Version : How do I blow a driver??

20-04-2012, 02:40 PM
Hi all

Rather than actually wanting to blow anything up, I was after a bit of guidance on what cock-ups to avoid!
As a novice I've just taken delivery of a system4 kit from Roy of DIYCNC.
From reading round these forums I've picked up not to mess about with motor connections with the power on.
Are there any other things to avoid that might not be obvious to the uninitiated?
If a motor stalls does that damage anything?
How necessary is it to use screened cable to the motors?
Roy's manual suggests starting off with the boards set to min current to start with.
Any input welcome, no suggestions are too basic!


20-04-2012, 03:08 PM
Hi Ian,

I have the system 3 from Roy and I know from experience that if you accidentally wire the motor up wrong it will blow the driver. In that case, and possibly with system 4 as well, the main chip was plugged into a holder not directly soldered so it cost about 10 to repair.

I used screened cable but I think that's not required. Someone will correct me I'm sure!

20-04-2012, 04:18 PM
Hello Ian,

Like Rcn says make sure motor phases are correct. Sheilded cable or unshielded won't damage the drives in any way but with unshielded you run the risk of introducing electrical noise into the system and control signals which can and will cause eratic hair pulling probelms and send you round the bend so just not worth skimping on.!!

Stalling motors won't do any damage what so ever to drives or motors.
NEVER disconnect the motors from drives with power ON,(this goes for any driver not just Roy's) 99.999% time it will blow drives.

Don't give them more than the drives rated Voltage or even the actual rated voltage as back fed current from motors when de-accelerating could blow them, best to leave a small safety margin IE 30V drives use 24V PSU. This why it's best to buy drives with spare capacity.
Setting the amps too high will just make the motors run rough and get hot, It may or may not on Roy's drive do damage(Doubt it.!) having them set too high but on most singel drive setups it doesn't hurt them just makes the motors sound and run awfull.!

Double check and triple check all soldered or crimped connections, esp motor connectors for the above said reasons and if you have any strange happenings while in use, like missed steps or false limit or E-stop triggers this should be the one of the first places to check along with ground connections.

NEVER run signal cables, either motor or limits, E-stop etc along side power cables IE Spindle power this is a sure fire way to introduce electrical noise and premature baldness.!!
Also don't cable tie signal wires together, just let them run side by side with small clearence.

ALWAY ALWAYS use a Star grounding system taking each ground connection back to one main ground point.You can run multiple grounds to a main grounding block but only one (fatter)cable should come from this to the main grounding point.
Only ground one end of sheilded cable and do this again to the main control box Star ground. The only exeption to this is VFD spindle cable and this can or recommended to ground both ends.

Hope this helps and don't be affraid to ask if your not sure.!! . . . . Avoid the magic smoke at ALL COST's. .:sorrow:

21-04-2012, 11:40 PM
Jazz, Routercnc
Thanks for the advice!
Still smoke-free and just had it spinning a motor on the bench (well, dining table) :yahoo:

Just have to bung the motors on the machine now...............



24-04-2012, 08:03 PM
One step forward, one stepper back........
Have now wired up all 3 motors with screened cable and am getting seriously weird results!
The x axis seems to be the centre of the problem - this motor performs some random stepping with no signal from Mach3??
The other 2 seem to be OK most of the time BUT I have had all 3 spinning when I click the RESET on the Mach3 screen to STOP them!
To track down the x axis thing I have swopped motors, driver boards, and motor connectors - none of which changed it so I think it must be a motherboard thing?
There aren't any settings in Mach3 I could have wrong enough to cause any of this are there?
HELP! :nightmare:

24-04-2012, 08:28 PM
Check your bios to see how the par port is set up to either epp or ecp. Try both to see if it makes any difference.

24-04-2012, 08:39 PM
See PM.!!

( Nothing dodgy Lads just offering help via phone has I can't look at screen long with my knackerd eye. . :sorrow:)

John S
25-04-2012, 12:37 AM
The Stevie Wonder School of CNC fault Finding.

25-04-2012, 12:51 AM
The Stevie Wonder School of CNC fault Finding.

John I feel more like Ray charles but if ya knew how true that was you would piss your self laughing, I'm sat in darkend room with sun glass's on rocking in the corner because I'm so bored.!!
Soooooooooooo much work to do, loads of G-code to create but can't look at the bloody screen for more than 2mins without eye's piss buckets of water.!

Suppose should do what the doc orders and go to Bed but can't bastard sleep for thinking about all the shit I've got to do. .Arghhhhhhh.

25-04-2012, 08:59 AM
Thanks to 2e0poz and especially Dean, who spent an hour on the phone with me last night - a case of the nearly blind leading the blind! :pirate:
BIOS was set to ECP, now EPP, no change.
Wasn't certain had loaded demo version of Mach3 from the Artsoft site so did that - no change.
Voltages between GND and DIR pins on xyz driver boards all were less than 0.2 or more than 4.8 when active.
Heres something else - I unconfigured the x axis on the ports and pins page (enable off, pins to 0, port to 0) and the x motor STILL grumbles and turns in the same way with no Mach activity! :worked_till_5am:
One other thing, the desktop is a 2.2GHz Compaq Presario. The drivertest program shows a message 'pulsing too fast' but the pulses per sec show as about 15000 to 17000 where I believe 25000 is required, BUT in Mach3 diagnostics page pulses is always within 10 of 25000. These seem to be contradicting messages?
Will have to do some work this morning but unless anyone has inspiration will post motherboard/BOB/cable back to Roy this afternoon (as he has suggested).
So it looks like I'll be back working on motor mounts tonight!
Thanks again

25-04-2012, 09:56 AM
Minor correction - desktop is 984MHz with 1GB RAM

25-04-2012, 10:55 AM
Bios needs to be set to ECP. . . Also are there any settings in the bios for any type of power managment on the fly CPU clock frequency changing type settings, will say something like EIST or C1E.? If so then disable them. 99% sure this isn't your problem now but it would be when you did get it sorted because Mach doesnt like the CPU being messed with while working.!!

Would completly eliminate the PC by try connecting to another (But not Laptop).
Also forgot to mention make sure the PC doesn't have Apple Quicktime or any Adobe products installed. Turn of any power management, screen savers etc and auto updates.

Few only took 30mins and 6 attempts to write that so must be better now, think I'll try and finish that welding now. :stupid:

25-04-2012, 01:59 PM
Hi Dean
BIOS set back to ECP.
Board winging its way back to Roy (now I know why it's called a mother....board)
Tune in next week for the next exciting episode!

25-04-2012, 02:09 PM
Minor correction - desktop is 984MHz with 1GB RAM

984MHz sounds very limited for mach3. I used to use a 1.4GHz AMD for the CNC computer. It appeared to run just fine on 25KHz kernel frequency, but I found when I switched to the 3GHz P4 I could get much higher step frequencies (i.e. feedrates) with the same kernel frequency.

25-04-2012, 02:30 PM
Hi Jonathan - you may be right, although on the Artsoft website they quote 1GHz and 512MB RAM. As a hobbyist with limited funds, I'm not too worried about speed at the moment, but if the machine is a potential source of problems then I'll need to look at it.

I'm still confused by the result of the Artsoft drivertest program and the Mach3 diagnostic page - as I said in an earlier post:
"The drivertest program shows a message 'pulsing too fast' but the pulses per sec show as about 15000 to 17000 where I believe 25000 is required, BUT in Mach3 diagnostics page pulses is always within 10 of 25000. These seem to be contradicting messages?"
Can anyone enlighten me?


29-04-2012, 12:18 PM
Just to update anyone interested:
Roy has tested the boards and says they are fine. He is making some more on Monday and will send me a new motherboard, but if the old one was OK I'm not very hopeful that will help. I did find a thread on here from routercnc in 2010 where he had some problems with a system3 setup that he traced to the power supply. Apparently that was missed steps rather than unrequested moves so may not be related.
Anyway I have asked Roy if he will send a new PSU when he returns the card as it seems to be the only bit that hasn't been swapped/eliminated.
Fingers crossed!