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

MP, Thanks for your reply. First of all, the board is out in the open, I haven't enclosed it yet inside a box. I wanted to get it working first. I have tried running the dremel from a different power point but to no avail. It's all on a single phase. I have picked up a few different caps for filtering such as 0.01uF, 0.1uF, 4700pF, 0.047uF and a .033uF. It was suggested to me to try each on on the power input on the board between the + and - terminals to try to find which one would filter out the specific interference. A trial and error senario. I am happy for any other suggestion you may have. Regards David

I have very little vibration. Nothing significant enough to affect the motors. I am using a switching power supply, does this make it more prone to interference? David

I have a strange problem! I have build my cnc, and I am using KCam to run it. When I use just a pen in the holder, everything works fine, but when I turn the rotary tool (dremel type) on, it sends it haywire, and it appears to send some type of interference or spikes through the board and affects the software. It either does weird cuts that are not there or tells the software that is finished before it even gets to it's first cutting position. As I said, if I don't turn the tool on, it all does as it should. It just appears to be interference from the tool motor. Anybody else had this problem? What is the simple solution to filter out what I think are spikes or electronic interference. I've tried different power points, but they are all on the same phase. Thanks all. David

I believe that this driver board can handle voltages up to 35vdc, which should be enough for most larger stepper motors. If you are going to go big, you would probably want to use bi-polar anyway as they have more torque. This is a nice home cnc driver board which works great. As for how to use mosfets as switches, I'm not that advanced with electronics but I know others on this forum are... Good luck, and have fun building it all. David

I use KCam at www.kellyware.com It is windows based, imports dxf plt etc and works out the tool pathways for you. My only complaint it that it doesn't have tool offset yet. It's shareware. No matter what software you use, it will take time to understand what you are doing, and lots of test cuts.... you know, trial and error. David

I was informed that a computer power supply is switching and not as good as an unregulated supply. How do I check current supply? I was using an AT power supply, and I was only getting about 10vdc with load. Also, I have another AT power supply that has very low volts with no load (about 3vdc) and I am told that it has to have a load to produce the full 12vdc. What is the easiest way to put a load on the supply to produce the full current? Thanks David

Sorry, another question. I may try to build a power supply myself. What sort of amperage do I require to run the driver and motors, or is related to the ratings of the stepper motors only which is 216mA at 24vdc per motor. (data sheet here if needed http://www.mitsumi.co.jp/Catalog/compo/motor/m55sp/1/text01e.pdf ) Thanks again. David

Thank you MP for your response, in fact thank you everyone who has has an input. As for a wiring diagram for 5 wire steppers, it was more trial and error after identifying the center tap using a multimeter, connecting this to position two of the individual axis connectors, then connecting the remaining 4 wires into positions 1,3,4,and 6. Then test and if no good, swap 3 and 6 etc until you get the motor moving in a consistant direction. In response to your questions about the stepper voltage, they are rated at 12vdc and 24vdc with a higher torque rating at 24vdc. I am assuming I just attach the 24vdc to the + and - terminals of the driver board (surely I don't have that wrong). One more question, when I finally get a motor to turn continually in one direction under the control of KCam, the motor seems to make one complete revolution then pause for a fraction of a second then go for the next revolution and so on. Shouldn't the rotation be consistant and smooth? If not, what have I done wrong? Thanks for your help. David Andersen

In addition to the above: I have changed around the order of the wires and am now getting rotation. It's ok on the z and y axis, but the x axis is a little choppy. There is also not a lot of torque (not enough to move the axis, but the steppers rotate in-situ without the axis attached (hope you understand what I mean). I am running the board on 12vdc (or it's probably more like 11.8vdc). Would the motors be stronger if I ran the driver board on 24vdc, and will that cause any damage? Sorry about the repeated posts. David

Ok, I've built the board, the cnc and I'm using Kcam. I have configured the pins on the LPT port. When I jog the different axis, I get movement at the correct motor, but, the motor won't turn in either direction. While I am jogging the axis, I can move the motor either way with a little pressure (less than when it's just enabled). I am using 5 wire steppers out of printers and I used the resistance method to work out which wire was which. Then I used a 12vdc power supply to step the motor by touching the negative wires one by one until I worked out the sequence for a full turn. I have attached the wires to the board in this order with 1 being in position 1 (looking at the back of the connectors with the wires pointing at you, and the power in position 2, then wire 2 in 3 etc. Do I have these position wrong? The home and limit switches all show up in Kcam's Port I/O data screen as working. I am using the 12vdc rail from an AT power supply. I think I've covered all the details. Hopefully someone can offer a solution. Thanks David