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Author Topic: Good transistors for making stepper motor driver  (Read 4870 times)
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Dallas
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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.
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Dallas
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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.
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Dallas
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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.


* tech-5-phase-pentagon.jpg (13.59 KB, 460x325 - viewed 249 times.)
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Hope these help.
http://arduino.cc/en/Tutorial/MotorKnob
http://www.tigoe.net/pcomp/code/circuits/motors/stepper-motors
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St. Louis, Missouri
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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.
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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.
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Dallas
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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.
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Dallas
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I'm "obsessing" on 50kHz because that is how fast I will have to step the motor for my application, as I said clearly:

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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.
« Last Edit: February 02, 2011, 10:41:31 am by BetterSense » Logged

Dallas
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There is a label on the side of it that states "5-phase stepping motor, 1.4A, .0072deg/step".
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Dallas
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What kind of motor is this?
Vexta. Grey.

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Where did it come from?
The robot on an AMAT RTP tool. An industrial robot.

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Is this some sort of specialty motor?
Apparently, since it's impossible to find cheap driver ICs for 5-phase stepping motors.

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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.

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How you you know it will do 50 KHz?
I don't.

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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.
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