High speed issues, 2 Geckos, 1 car battery, 1 step up converter

[cjmerlincnc]

Hi, Getting high revs from steppers is a function of voltage so raising the voltage will enable you to get more speed. Having said that, you will find larger steppers will not rev as high as smaller ones. Sometimes it is better to use a slightly smaller stepper with the right gearing to attain a higher speed.

If you are using batteries as a supply, adding larger capacitors will not help attain more speed.

Capacitors are only used to smooth the ripple on AC driven power supplies as more current is drawn from the supply. They also soak up the back-EMF produced as a motor decelerates. If you do not have enough capacitance, B-EMF will raise the voltage of the supply or as you draw more current from an AC driven supply you will get more ripple, lowering the available voltage that the motors can use.

Unless you use some trial and error method by changing components, you really need a scope to see whats going on.

Using batteries as a supply is a good idea for testing as you wont have a ripple problem.

Try making the wires from the drive to the steppers as short as possible and with as large a diameter as you can fit in the drive terminal block.
Same with the supply wires.

You mentioned that adding a capacitor near the drive helped, maybe your wires are a bit too long or too small.

I would be inclined to borrow a few batteries and raise the voltage to 36v.



Regards

[poptarted]

A single motor runs just fine from a 24 V AC-DC power supply with a 10k uF cap on the supply terminals.

2 batteries in series to make 24 V work fine too.

Adding in the step up converter means switching is occurring, but that in at 54 kHz. So it is an AC source in that sense, but I'm not sure. I assume that the 80000*I/V was derived from 60 Hz full wave, so I guess if I have a 54 kHz driver I'd use C = 10e6*I/(2*f*V) = 10e6*6/(2*54e3*24) = 23 uF, which may or may not be significant at all. So I guess if I'm testing from an AC source through the Step up converter, I'd need ~20k uF per motor and it should be something small from a battery.