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3-Axis Stepper Controller


alberto
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Mikromike, I have never used the software package you are using, so I cannot comment on that. However, I did want to mention that by testing functionality with the 555, you have verified your CNC hardware is ok and that the problem is isolated to the computer. Are you sure the software is sending pulses to the correct port pins? I always recommend making a small board with LEDs on it to connect to the computer port for testing the pulses before connecting to any hardware. It sure makes life a lot easier.
ALSO NOTE: The normal speed that is used to turn a stepper is too fast to view the individual pulses on LED or with a volt meter (as greekpic has stated). You always have to slow the pulses down to a very slow speed to be able to watch them. If your software has this capability (and most do) then you will be able to see the pulses at the port.

MP

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I'm not sure what you mean exactly. Both in the board and the schematic there are four diodes per axis facing from pins 1,3,6,8 towards the motors which are connected to the green terminals, to answer your previous question. Pins 2 and 5 on the connectors are common, so if you have a 5 wire motor you leave one unused. I'm pretty sure I got it right since it works.

The 4k& networks are 1+7, pin 1 goes to the square on the layout picture (I overlaid the layout on the PCB and printed it, it really helps).

My TurboCNC settings are:
[AXIS1]
Designator=X
StepIncrement=0.001000000000
IsLinear=True
IsStep/Dir=True
PortAddress=$378
StepPin=2
IsActiveLow=False
Pulsewidth=15
DirPin=3
LowIsPositive=False
Acceleration=1500.000000000000
StartSpeed=400.000000000000
MaxSpeed=2500.000000000000
Fast_Jog=500.000000000000
Slow_Jog=50.000000000000
HomePosition=0.000000000000
HomeInPositiveDir=false
InvertJogKeys=NO

[AXIS2]
Designator=Y
StepIncrement=0.001000000000
IsLinear=True
IsStep/Dir=True
PortAddress=$378
StepPin=4
IsActiveLow=False
Pulsewidth=25
DirPin=5
LowIsPositive=False
Acceleration=2500.000000000000
StartSpeed=500.000000000000
MaxSpeed=5500.000000000000
Fast_Jog=500.000000000000
Slow_Jog=50.000000000000
HomePosition=0.000000000000
HomeInPositiveDir=false
InvertJogKeys=NO

[AXIS3]
Designator=Z
StepIncrement=0.001000000000
IsLinear=True
IsStep/Dir=True
PortAddress=$378
StepPin=6
IsActiveLow=False
Pulsewidth=25
DirPin=7
LowIsPositive=False
Acceleration=2500.000000000000
StartSpeed=500.000000000000
MaxSpeed=5500.000000000000
Fast_Jog=500.000000000000
Slow_Jog=50.000000000000
HomePosition=0.000000000000
HomeInPositiveDir=false
InvertJogKeys=NO

This is a part of my Turbocnc.ini file. I haven't tried to find the best setting for speed and acceleration yet. Also as you can see I've tried a pulsewidth of 15 and 25 ms, both work fine and I think it can go lower (for better performance).

Hope that helps,
Nikolas

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  • 2 weeks later...
  • 3 weeks later...

Hi, First time posting here, but I have a quick question.

I have made the pcb and I am just about to populate it. Someone suggested to me that I should use opto-isolators to protect the motherboard from power spikes.

Is this necessary?

Has anyone else had this happen?

Has anyone redesigned the board to have opto-couplers?

Thanks for your help.

David

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  • 2 weeks later...

I hope people still read this forum, haven't had an answer to the above question yet.

Anyway, here's another one regarding limit switches.

Attached is an altered version of a diagram that was posted earlier, what I need to know is, with three limit switches for x,y and z are they wired in series as shown. (excuse the poor artwork)

post-5861-14279142005395_thumb.jpg

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David,
The forum was loading pages real slow for a week or so and people were not posting. In answer to your question about opto-isolators, some recommend to never connect your PC to the outside world without isolation. However, I never use isolation on my personal devices and I take a high chance by doing so. When producing something that others will use or build, I always add isolation in case something gets mis-wired. All of my CNC equipment is used on older type computers which use cheap parallel port cards. The worst that can happen in such a case is to ruin the card and replace it with another. I might add that I have never burned up a card or had to replace one. If you are making something to connect to your $1500 home computer, then you might ask yourself: Do I really want to replace the motherboard? Usually in newer PCs, the parallel port circuit is embedded on the motherboard.

MP

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  • 2 weeks later...

Hi to all of you, i know that i'm late but please, be patience....

How works the Home switch?? The driver goes around until some sensor tell that it is the home position or else??
Do i have to set up the home position each time?? if yes HOW?? i can't handly move the axies...
The driver works with home switch open, closed or they are irrelevant??
Thank you for any answer.

KingKanzor

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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

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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

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RobiD: more voltage -> more torque, just don't exceed the motors specifications. You might also try different pulsewidth settings, the motor might be stalling.

kanzor: In TurboCNC when you home the axis moves untill it trips the home switch, then resets to 0 or any other preset value (e.g. you wouldn't want Z to home on the table, you would set it to go + (up) and resset to whatever your Z travel is.
It is not neccessary to home every time (the position is stored when you exit the program) but it is recomented for better accuracy.

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David, I cannot comment on the voltage for your motors without a data sheet. However, if the wiring is not correct, the motors will not move. You should check the wiring a few times to make sure you are connected to the correct winding. If you are sending 12 VDC to a 5 volt stepper, this is not a good idea. Are you sure these are 12 volt steppers?
Another cause for not getting motor movement is to have the speed of the motor set too high. Try setting the delay between steps to a higher number. I am not familiar with KCAM, but there should be a setting for speed or delay. If the motor is getting the pulses too fast, it will jog when you give it a step manually, but it will not run.
It would be nice if you could post a diagram of your setup for the 5 wire steppers for others in the forum.

MP

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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

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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

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The inconsistency of your motor rotation might be due to not enough current. Setting the speed too high can also cause this.
For a power supply, I usually use an old computer power supply. They are cheap, run cool, and have plenty of current at 12 volts.

MP

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