3-Axis Stepper Controller

[RobiD]

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

[ante]

Hi RobiD,

One easy way to load a PC PSU is to put a 4R7 10W on the 5Volts side. This works on most ATX and AT PSUs. If you look at the label on your PSU you can see the ratings on the different voltages.

[rdmotors]

My question abou this circuit is: Why are the input lines to the ic have 5v resisted supply on them? The restistors I am talking about is RP1-3. it would seem that you would back feed power into your lpt port? Or am I way off base?

[MP]

Your parallel port data pins are logic levels. The 5 volt through a pull-up resistor insures the lines are tied high until the port pin sets it low. This is a standard configuration for logic. You are not feeding power into the parallel port. However, if your software is setup to read the pins on the parallel port instead of send, then yes, you will be feeding the voltage into the port to read it. This is a bi-directional port. Whether it reads or writes is up to the software in the PC.

MP

[madthug]

Uhh... at the risk of sounding stupid, what program can be used to open the "___.ps" file exention?
Thanks,
MadThug ???

[GreekPIC]

I open them in Corel Draw. Adobe Ilustrator will do too, and many programs can import it (even Word if you added the appropriate filter during install).

[madthug]

I just wanted to thank GreekPIC and MP for supporting this project for free. I'm excited to get started on my own gantry mill.
-MadThug ;D

[GreekPIC]

You 're welcome. Good luck with your project and post updates

Nikolas

[MP]

Hope to see the results of your mill.
Good luck!

MP

[Dazza]

Hi all,

I have been wanting to make this project for a long time, but had no use for it until now :D.

Okay I want to start with getting familiar with the software, which leads to my first question, with probably many more to come ;D.

I am a slow learner when it comes to software :(, so what would be the most user-friendly software to use ???, I prefer Windows based software, anything else will scare me :o ;D, and preferably freeware/shareware to get me going ;).

Thanks in advance.

[RobiD]

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

[Dazza]

Hi RobiD,

Thanks I installed KCam ;), looks like a lot of learning for me, with plenty of that trial and error ;D. My OS is XP so I'm not sure how it will go, I may have to find something else but at least I now have an idea of what I am in for :o. I only have the one computer to use to get the milling machine set up, then I will buy a cheap computer solely for the milling machine.


I want to use it for milling timber and foam patterns for metal casting, I first want to make a very basic scale model, then make the larger mil that I will need. It's likely that I will need motors that will draw more current then this project can handle :-\, there shouldn't be any problems if I use power transistors or could I use MOSFETs to drive the stepper motors via triggering their gates? Accuracy wouldn't be lost by doing this?

[RobiD]

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

[Dazza]

I have just noticed that this project calls for, (3 resistor network 770-81-R-4.7K) is there an alternative to using these components. As they are not readily available to me, these are basically resistors configured in a certain way?, can I use resistors if so how do I configure them?

[GreekPIC]

They are actualy seven 4k7 resistors with one pin of each resistor connected to a common pin. You can use discrete resistors, though I don't think there so hard to find. Don't search for the specific code, ask for a 1-7 resistore network.

[RobiD]

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

[Dazza]

Hi RodiD,

The cause of the problems may not be interference or spikes, it may be possible that the vibrations from your cutting tool, is causing one or more of your stepper motors to trip a step, throwing your software collaboration with the stepper motors. It's just a thought, I am still only in the research stage of this project, so I could be way off.

Are you experiencing any significant vibrations?

[RobiD]

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

[MP]

RobiD,
Describe your circuit board for the CNC. Is it mounted inside a metal container? Motors combined with digital circuitry is a hard combination in many cases. The circuitry must be shielded from electronic noise. You are probably right about this being interference from your Dremel. If you have shielded your circuit and this does not help, you might also want to try plugging the Dremel into a different power source. The feedback might not be RF. It might be noise in the AC line caused by something in your Dremel tool.

MP

[RobiD]

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

[RobiD]

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

[Mikromike]

RobiD,

Are you using a new Dremel or a old one. Also recheck for loose wire connections. I had the very same problem it turned out to be a loose wire that was only affected from the vibration. Mike

[Dazza]

RodiD,    have you tried running your mill with the pen in the holder, then running your rotary tool at a distance connected to the same power outlet? This may help narrow down possible causes of the problem.

This may confirm or eliminate the problem being a loose connection, as Mikromike suggested it could be.

[MP]

Is it possible for us to see your board layout?

MP

[RobiD]

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.