Uln2003

[ipodman1991]

Well, ive finished my mechanical system for my cnc machine, and ive been looking for a simple stepper motor driver. I made another post a couple threads back for another cnc board, this is a new one.

the site i link to shows how to control a stepper motor with a ULN2003. ive looked it up, and its apparently 7 darlington transistors. its super easy, so it would be ideal for me, a more mechanically inclined person.

http://electronics-diy.com/stepper_motors.php

how well do you think it will work?

[Mariss Freimanis]

Not so nice (quoting Borat) if your motor is not:

1) 12V to 24V rated (read 'tin-can' motor).
2) Has a phase current rating of 200mA or less (read 'very small motor')

The ULN2003 is best suited for low current NEMA-17 and smaller motors. It's a little IC with no heatsinking capability after all. We use them in the G100 as relay coil drivers rated at 100mA max.

Mariss

[jans123]

If you want to try CNC ina small scale I would say go for it. My first system was build on that device. The steppers I used came from 5.25" floppydrives. I cheated a lot there. I made a rigid coupling betwen the motor axle and the M4 screw that I used as a starter and let the bearings in the motors take the axial load. (Yeah it was a quick and dirty job but it worked and it was a zero-budget). The nuts was tapered 4M holes in a piece of brass, exempt for one, I run out of brass so I took a pice of aluminium and it lived a hundred hours or so. Quite enough for my test. The spindle was a simple chinese grinder where I could fit tools with some 3mm shafts -I think it was... The software was Turbo CNC from www.dakeng.com and that worked perfect on the old computer I used. I even nicked the 12 volts for the motors from the computers power supply (It was 12V motors).
The only advice I can give you is: take the oldest DOS computer you can find, be careful when wiring the cables to the parallel port and yes, with Turbo CNC, one printer port can handle 12 bits, that means 3 steppers with your electronics or 6 steppers if you build some real electronics!
If you want the steppers to run faster, use 24V and add serial resistors with each winding to reduce the current. (There is a revers voltage induced in the windings when the stepper is pulsed and that reduces the torque with increasing pulserate. By adding higher supply voltage you can over ride it a bit, but you will have to reduce the current when the motor is not pulsed, hense the resistors).
The motors was small but with the fine thead of the M4 screw I got a force that I never believed was possible.
Good luck and whatever you do, remember: safety first!
/jan