[NeoMoses]

This kit appears to be worth taking a look at: http://www.mpja.com/productview.asp?product=8479+KT

I'm pretty much "electronics retarded" so I don't know if this would work for our uses or not... but at the price, it definately caught my attention.

There are also a couple other ones to look at.

http://www.mpja.com/productview.asp?product=8413+KT (very promising looking)

Servo Driver (Might be good for cheap power feeds...)http://www.mpja.com/productview.asp?product=8402+KT

There are also some relatively inexpensive relay board kits that would work well for coolant/spindle/other accessories on a CNC. I'd like to hear back from some of the electrical gurus on whether or not these may work for PC controlled CNCs.

[Mariss Freimanis]

None of those will do much more than make the motor turn. The power involved is simply too low to give significant power at the motor shaft. The first one may be suitable if you can live with very low motor speeds. Be warned, you will need a pair of large power resistors (20W to 100W) if used with higher current motors. These will cost more than the drive.

Mariss

[NeoMoses]

ahhh, another one of those, "You get what you pay for" things, I see. Daggummit! (chair) Well, you can't blame a guy for trying. Thanks for the tip, Mariss. Guess I'll still be recommending your products. (I'm a satisfied customer.)

[Mariss Freimanis]

Thanks, but I'm not trying to make a pitch for my drives. Any good switching type bipolar drive, ours or someone else's, will outperform these R/L drives by a very wide margin.

Sadly, it is a law of nature that there is no free lunch. Switching type drives are far more complex than L/R drives and thus cost more.

Things to look for when you see a deal that seems to be too good:

1) If there is a picture, count the power transistors. Anything that has only 4 power transistors will be a unipolar drive. Count the motor wires going to the drive, a bipolar drive needs only 4.

2) Look at the heatsink size. If you see those little clip-on heatsinks or none at all, then you know very little power is involved and little will be delivered to the motor. This applies to the dongle-looking drive. It's small and it is plastic. Where is the heat going to go?

3) High current ratings without high voltage ratings means low power. Power is voltage times current.

4) Use a figure of merit to get a rough idea of a drive's value. Multiply the rated per phase current times the rated supply voltage and divide the result by the price of the drive. Compare that against other drives' figure of merit.

5) If everything else is equal, pick a microstepping drive over a full or half step drive. The microstepper will always run much more smoothly at low speeds.

Mariss

[kfong]

Definitely go the microstepper route, lower motor resonance and smoother performance.

Try this, 3amps and up to 55volts. The nice thing is it is a microstepping chopper driver board. Software is open source and the design works great. Very smooth at 8 microsteps.

http://www.embeddedtronics.com/microstep.html

Kin Fong
http://www.embeddedtronics.com

[vacpress]

I have experience with this question:

I built several drivers jsut like the first link you posted - the $15.00 device. They were a bgreat learning tool - easy PCB to design and make - and making steppers spin "alll on your own" can be very rewarding.. However, they are slow, run hot, and most likely loose steps.

I have also used a xylotex board, untill i blew it. The $40 xylotex seemed very nice for the 10 minutes it worked. It runs much faster and cooler than the unipolar.

I have also used the gecko g201s.. These drives are very impressive for the cost, as we all know. For $114/axis you can get a driver you will not grow out of unless you move upto a large gantry mill.

The embedded electronics device is a cheaper alternative to the xylotex and likely delivers similar performance, but it looks like you need to know a fair bit about 'tronics to get it running reliably.