Trouble getting Picstep to run...HELP Please

[barmybovine]

Another thought I had. I got the pics for this project a long time ago as free samples. They are pic16f628a i\p chips. Does anyone know if it might be this particular version of the chip that might be screwing me over ???

Thanks

[pminmo]

#1, forget what your read with a current meter. You can't establish much as the current will vary depending on motor, where the phase is stopped, power supply voltage...........
Your PIC's are fine. Take one PICstep, a motor, set the max current resistor appropriately and watch your power supply voltage to see if it drops at the LMD power connections while the motor is running.
make sure your 5V is ok at the dac input of the picstep.
Make sure your power wiring from your powersupply to your picstep boards arent daisey chained, both + and gnd.
What result did you get with half coil?

[barmybovine]

Thanks for your reply and very appreciated help on this Phil and all who have replied.

I had done a previous load test on my power supply I have a high wattage 3 Ohm resistor and managed to draw around 12 amp from the supply without significantly loading it down. 35v dropped to 33.7V . The transformer is a 500VA 24volt so it could do more current if required. I also went ahead and tested at the picstep motor inputs and there is no voltage drop to speak of whilst running my motors.
At half coil they stalled out at about half the speed of full coil.

Maybe I am just expecting to much of these motors. I have managed to get them running around 40ipm with reasonable torque.But just expected to get a little more from them. I am using ACME which I understand is very inefficent in terms of transfering the power from motor to axis. I took your advice Phil and decided to ignore the my current readings. Its just a habit I guess of checking things out before running a new piece of hardware. I just expected to draw more juice through them than I am . Even whilst loading the axis I only observe just over an amp drawn before my motors stall out.
Also I decided to go with THK rails as I found a reasonable deal on Ebay.
I was suprised when I got them (even the brand new ones) at how much resistance they seem to have. I had previously built a set of bearings using roller blade bearings and some angle, which you could push gently with one finger and would glide from one end of the table to the other. That certainly isnt the case with these THK HSR bearings they only roll a few inches with the same kind of force. As you can see in the pic of my table ,there is a reasonable amount of weight in the gantry (mostly 5\8" aluminium and 1\4" steel angle). Maybe thats all I can expect with these small motors.

I think I will see how I go with what I have now. Hopefully be able to cut wood @ ~ 25ipm????? Learn to use and program the thing and them get either bigger steppers or go the whole hog and get me some servo's. Maybe I cna do some first cuts this weekend

Thanks for taking the time to help me on this and I apologise if I got a little frustrated for a while back there You know how it goes.......almost there and then something always crops up to say "not so quick matey" ...........Once again THANKS guys

[pminmo]

barmybovine,
You should be getting much better performance than you are, that I would agree. I have to believe there is some common issue. The reason I say forget the measured current is you just can't get a valid reading without a true rms meter, due to the chopping. The PICstep is a very good driver, and with your motors running it in series bipolar you should get better perfromance. Several things disturb me in the information you have provided. Running that motor at 3A half coil should give you a bunch more than you are getting. I've run 6 wire motors at 50% the rated amperage phase amperage with excellent results at half coil. I did so because the motor coil voltage rating was high, and the series bipolar inductance was high. While the picstep won't give you what the motor is fully capable of (bipolar parallel) I would think you should be able to do 70+ips rapids no sweat.
The motor rating I found with the label, shows those motors with real low coil resistance, and you should have seen a performance improvement changing wiring. My suggestion would be if you have access to a scope, review the current sense output.
Another thought would be if the current sense resistors have an inductive component, that could cause you a problem. They need to be either carbon comp or film resistors.