Stepper motor driver issues (Electronics Goldmine stepper motor G14197)

Hello,

I'm having some issues getting this little guy to run:

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The site says this is a 2-phase bipolar stepper motor. Has anyone used this model before ? I've rigged up the schematic provided:

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but it doesn't seem to work. I've double, triple checked the circuit, but the motor just won't work. It seems to me that there needs to be some sort of grounding or V+ applied to one of the windings of the motor ?? but I'm not sure...

It would be great if someone who understands this stuff could take a peek and let me know if I need to add something to the circuit over and above what the schematic suggests.

Thanks a lot !

Best, Vignesh.

Reply to
Vignesh Ganesan
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In message , dated Mon, 7 Aug 2006, Vignesh Ganesan writes

The supply volts and ground come from the buffer 74HC365. You need an oscilloscope to diagnose this circuit; have you got one?

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Reply to
John Woodgate

Well, the schematic of the motor that's embedded in the driver schematic is certainly wrong -- and I'm not too sure about what they're having you do with the 'bias current'.

With five wires it's probably a unipolar stepper with a common center tap on the coils. The common center tap will prevent you from driving it as a bipolar stepper without more work than it's worth.

I suggest you spend some time with an ohmmeter to figure out how it's hooked up, then spend some time with a battery and some switches to figure out how it works. Once you find common you should be able to put it through it's steps by switching each coil on in the right sequence.

Then do some web searching on unipolar steppers to find the _right_ driver circuit. You should be able to come up with a circuit pretty quickly.

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Tim Wescott
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Reply to
Tim Wescott

Lessee.... (1) photo shows 4 leads, (2) first part of "description" says 5 leads, (3) later part of "description" says 4 leads, (4) the PDF shows 3 leads, (5) the text mentions 2-phase, (6) the PDF shows 3-phase. I *do* like the consistency! So...*IF* it is indeed 3-phase, then there is only 3 leads as shown in the PDF and a true 3-phase drive is needed. On the other hand (or is that "on the other phase"), if it is a

2-phase 4-lead motor, an H-bridge or equivalent is needed to drive each half (or coil if you insist) first one polarity and then the other with possible times of no drive current.
Reply to
Robert Baer

Thanks for the reply John.

No, I don't have a scope, I'm planning on hooking up a couple of LEDs with some D-Type flipflops and coming up with a frequency divider -- that way I can atleast be sure that whats coming into the line driver (74HC365) is a clock pulse.

Best, Vignesh.

John Woodgate wrote:

Reply to
Vignesh Ganesan

The consistency is superb!... :-) I'd suggest that if the original poster has an ohmeter, the best place to start, would be to try to work out the coil arrangement for themself. First question. How many leads are there on the motor?. Second question. How many leads go into the plug?. I think there are really two possible layouts, assuming that the plug is four pin. The first is that there is one 'common' pin, and three winding connections (as shown in the schematic). If so, with the meter attached to the 'common', the other three pins sould have almost equal resistances shown. However the description, and the look of the motor, fits with it being a normal bipolar motor (the sort used in many cases for the head positioning in old floppy drives), possibly with six leads at the motor, and only four connected to the plug (if it has got six leads, then it can be used with either bipolar or unipolar drives). If this is the layout, then there should be simply two 'pairs' of pins at the plug, with a winding between each pair.

Best Wishes

Reply to
Roger Hamlett

Hi Robert,

Thanks for the reply !

So then, assuming what I have a three phase motor, then is the schematic correct ? Or are you implying that this isn't the schematic for a "true 3-phase drive" ?

Got it. I'm looking up the schematic for the h-bridge, will get to work on that this weekend !

Thanks a lot ! Best, Vignesh.

Reply to
Vignesh Ganesan

Hi Tim,

Neither am I !! That really threw me off !

Alright. I'll do that and figure out what these leads are. Once that's done, I guess I ought to be able to come up with a unipolar circuit. Btw, is this a correct circuit for the unipolar motor ?

Reply to
Vignesh Ganesan

There are 5 leads coming out of the motor -- R, Y, B, Wh and Bl.

5 go into the plug. There are 4 points in the plug -- two of the leads (the Wh and Bl) go into the same point in the plug.

I'll measure the resistances, sure.

I guess if its got 5 leads at the motor and only four at the plug, that

*still* makes it a bipolar motor ?

Thanks, Best, Vignesh.

Reply to
Vignesh Ganesan

No. Frankly I'm not sure what motor it might be a correct circuit for, and if it is a correct circuit for some motor, if that motor could exist in this Universe.

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Tim Wescott
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Reply to
Tim Wescott

Well I'll be dipped.

I'm sorry, I was steering you wrong -- I read as far as "five leads" and assumed that it was a unipolar stepper with a common ground -- but that would only make sense if they brought all five leads out to the connector.

It may, indeed, be a 3-phase stepper. Although I've certainly never heard of such there's not reason it can't be done.

If this is the case then:

(a) The blue, yellow and red leads should all have about the same resistance from lead-lead. If it's a 'Y' connected motor then the black and white leads together will probably have about 1/2 that much resistance to each of the colored leads.

(b) Their schematic should work. It's not really a three-phase driver, but it should work. I think you mentioned putting LEDs on the outputs

-- if you slow the clock way down you could see them blink.

(c) Jeeze that's a weird clock circuit!

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Tim Wescott
Wescott Design Services
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Reply to
Tim Wescott

The more I think about it, the more I'm inclined to think this is a '3 phase' motor, designed for something like an aircraft. There are 400Hz 3 phase low voltage supplies, used in quite a few avionics parts. As such, it can probably be driven as a stepper, but is probably designed to really have three sinusoidal phases, rather than simple 'steps'...

Best Wishes

Reply to
Roger Hamlett

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