Good transistors for making stepper motor driver

[BetterSense]

I have some big, 1.5A, 5-phase stepper motors and I need 10 transistors each to make a stepper driver for them. What kind of transistor do I need for a high-power switching application like this? And hopefully not too expensive.

[BetterSense]

Well, I guess I have to figure out how to drive the damn thing first. There are only 5 wires...red, green, blue, black, and orange. I'm not sure if I need H-bridges or half-bridges or what.

[BetterSense]

Ok this is the circuit I found.



I think those transistor pairs are called half-bridges.

So, will those PNP and NPN BJTs be fast enough to switch at like 10kHz directly off a microcontroller (50kHz is needed for 60rpm on this motor)? These vexta steppers are all over the place in semiconductor mfg equipment but such a pain. Compared to normal steppers.

[dnc40085]

Hope these help.
http://arduino.cc/en/Tutorial/MotorKnob
http://www.tigoe.net/pcomp/code/circuits/motors/stepper-motors

[marzetti]

Take a look here: http://www.cs.uiowa.edu/~jones/step/. Jones seems to be the defacto stepper authority on the internet. A link to his site should probably be included somewhere in the Arduino site.

[rocketgeek]

Well, I guess I have to figure out how to drive the damn thing first. There are only 5 wires...red, green, blue, black, and orange. I'm not sure if I need H-bridges or half-bridges or what.

You need a half-bridge on each. See the Jones link someone else provided for more on how to drive it -- five phase motors are kind of weird.

[BetterSense]

I'm pretty sure the circuit I posted above is what I need to drive it, but I'm not sure if the picture will show up if you aren't signed in. I'm just worried I won't be able to switch the transistors at 50+kHz, or that the motor won't work properly at that speed without a proper 'chopper' drive system.

[BetterSense]

I'm "obsessing" on 50kHz because that is how fast I will have to step the motor for my application, as I said clearly:

will those PNP and NPN BJTs be fast enough to switch at like 10kHz directly off a microcontroller (50kHz is needed for 60rpm on this motor)?

The motor is .0072 degrees per step, so I need to step it at 50kHz to get 60RPM. I'm not sure if I will be able to do this with a simple switching controller so it's a real concern for me. I said nothing about PWM at any point; you came up with that out of the blue.

[BetterSense]

There is a label on the side of it that states "5-phase stepping motor, 1.4A, .0072deg/step".

[BetterSense]

What kind of motor is this?

Vexta. Grey.

Where did it come from?

The robot on an AMAT RTP tool. An industrial robot.

Is this some sort of specialty motor?

Apparently, since it's impossible to find cheap driver ICs for 5-phase stepping motors.

Is it really .0072 deg/step without microstepping?

I think it's .72 degrees, but it has an integral 100:1 gearbox. There appears to be no way to remove the gearbox.

How you you know it will do 50 KHz?

I don't.

That also seems extraordinarily unlikely

Lame. I wanted to make an RC lawnmower. I want at least 2 m/s. With 30cm wheels, I need about 60RPM. I was going to make a driver with 10 transistors and an ATtiny, but maybe I should forget the whole thing.