RE: [CAD_CAM_EDM_DRO] XY-8080/Controller/Motor Questions

> A few questions:
>
> 1. I assume that this controller does tricks and probably has a
> sophisticated ASIC or something like that soing some sort of PWM, or
> maybe the pulses are stepped like a sawtooth (high voltage to move
> the motor, then back to something lower) although I didn't look at
> the output on a scope yet. I can't look inside the drives because the
> package is an integral heat sink and is potted. But how can I set
> this up for maximum power without letting the magic smoke out of the
> controller or burning up the motor.

Normal output is full power all the time. Some drives will have idle current
reduction but it will not kick in on every step even if you are moving quite
slow. Most likely the drive is just a pair of H-bridges with a either a
microcontroller or an ASIC (plenty of off the shelf chips available)
translating the step and direction signals to the phase signals needed for
the H-bridges. Assuming you don't power them with more than the drive can
handle voltage wise the motors will start to tell you when the current is
getting too high by heating. Most stepper motors can tolerate temperatures
beyond which you will feel comfortable driving them. Just up the current a
little and run them for 10 0r 20 minutes and see if the motors are heating.
I don't like running them hotter than I can touch, but that is well under
the rating of the motors I have seen specs on. If you don't have idle
current reduction the motors will get hotter faster when sitting still and
slower when moving rapidly.

> 2. I'll probably get a proper power supply for this set up. But how
> many amps would be enough? I assume that the drives/controllers have
> anti-back EMF stuff built into them, but I think that switchers just
> dont like inductive loads (and they certainly don't have the brute
> force reliability of a good linear). Linears are getting harder to
> find and expensive. Any experiences?
>
> Does the power supply for the motors even have to be tightly
> regulated? would a big-a** transformer, and a very beefy bridge and
> giant cap do?

Linear is the way to go. A transformer, bridge, and a cap will do the job.
Dan at Camtronics has some nice new 10 amp 24 V transformers for $40 that
will build a dandy 36 VDC power supply if you add a 20 or 30 amp full wave
bridge rectifier and a 10,000 uf or so cap.

> 2. Assuming that I'm not going to be using these for any heavy-duty
> purposes (drilling/routing PCB's), is there any
> advantage/disadvantage to running less than full power. I assume the
> risk of dropped steps and lower max speeds is there.

Now you are getting into the weirdness of steppers. Lowering the current
will reduce the holding torque, but will have very little effect on the
running torque until you reduce it quite a bit (more than 40 - 50% of the
rating would be my guess). Raising the voltage will increase your maximum
rpm because the higher voltage will help to overcome the inductance.

Tim
[Denver, CO]

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