RobiD

It definitely is not that exciting for a 5 hour trip. It's been many years since I've been to Bundaberg. It's a nice part of the world from there to the top. David

Dazza, Where in Queensland, I'm on the Gold Coast.

Hey Dazza http://pminmo.com/ I am going to build the descrete.html X 3 and the Interface - 4 axis - modular BOB (break out board) There is also a discussion forum which is also very helpful. By the way Dazza is a very Aussie type name, are you in Australia? David

Thanks for everyone's input with this project. I have decided to build a driver that can run upto 6A motors in a modular design that I have found. I really enjoyed building this one as it gave me lots of knowledge. I figure the UCN cooked from too high a current draw. I have lots of these 3amp and 3.25amp motors and I need to build something that can handle them. Thanks again everyone. David.

Thanks for your reply MP. I rechecked the motor and it's only 1.2 amp. Should it have been able to handle it? What about the power supply setup, would this have had any roll. If I want to run 3amp motors, (Unipolar) what is the best way to do it? Further advice greatly appreciated. David

Well, it really does give out smoke. Maybe someone can tell my why. I have been running the board on 12vdc from a computer powersupply. I read an article on how to put 2 computer PSU's in series to make 24vdc. Followed the instructions and it produced 24vdc. With the new motors I mentioned above, they like 24vdc. I made a heatsink with aluminium U channel, used heatsink compound and mounted a fan directly above. I connected one of these motors to the z axis chip (this one was rated at 1.8amp) and when I powered it up, it cooked the UCN. I had run the PSU's like that for a couple of hours to make sure it was reasonably stable and it was. The pins that cooked on the UCN were pins 2 and 3. Does heatsink compound conduct electricity? (probably sounds like a stupid question) The driver board has been running as it should up to this moment. What other reasons could cause this. Thanks for the input in advance. David

I have 3 x 24vdc 3.25 amp and 3 x 24vdc 3.1amp SanyoDenki motors. What is the highest amperage that is ok to run with this board? David

I did have 3 NMB PM55L-048 by Minebea but these were missing steps due to poor torque. They would hardly make the UCN's hot. I came across some Sanyo Denki Step-Syn motors which have a higher torque rating and a higher amperage per phase. These are 24vdc motors but at the moment I am running them on 12vdc. Even with the first motors, I was cutting 4.5mm perspex in 3 layers (you know 3 cuts at lowering depths - can't think of the term). It would cut but as I said, it would miss steps and when it went back to x0,y0 it would be out. David

Yeh, I'm interested in this question also. I've put stronger motors on my CNC and now the UCN's are getting so hot the motor cuts in and out, so now I have to put heatsinks and a fan over them. David

All is good with the new dremel now. Thanks David

Just an update. Everything works fine if I run the dremel at a slow speed. Only problem is it pulls the cutting tool through the work faster than it can cut. I have slowed down cutting speed, but if I go any slower... well you know. There must be a simple solution. David

Maybe I misunderstood what you asked. Here is a link to the project: http://www.electronics-lab.com/projects/pc/008/ I had taped all three motor leads together, I undid this and there is an improvement, now when the motor is running, the z axis goes to, say the cut is -1.5mm, it will lower to 3mm from 5mm and begin it's run. Without the dremel running, it goes to the correct depth. It gets frustrating when you feel your not moving forward. Thanks for your help David

My board layout is this 3-Axis Stepper Controller, built exactly as specified in this project. For power, I am using the 12vdc output of an old AT switching power supply which is just placed next to the board on a table as to utilise the fan from the PSU to cool the chips on the board. I am using ribbon wire for the limit switches and 8 core solid communication cable to the motors. The printer port cable runs under the table to the computer. The PSU and computer share the same power point and so did the dremel, but have tried seperate power points to no avail. I hope that is what your asking.

MP, Just another thought, I just read an article on shielding electronic boards from interference, and it mentioned that switch mode power supplies (of which I'm using an old AT power supply) can cause interference in circuitry. I have the PSU pushed up against the board and am using the fan from it to cool the chips. This still doesn't explain why, without the motor running in the dremel, the cnc will run through 4000 lines of g-code without skipping a beat, but as soon as I turn the tool on, it all goes bad. David