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From: Anthony Fremont
Subject: Re: How to determine the " common " of a Teac Motor taken out from a 5 1/4 disk drive??
Date: Sun, 19 Jan 2003 17:00:35 GMT
NNTP-Posting-Date: Sun, 19 Jan 2003 11:00:35 CST
Organization: Road Runner - Texas
> I am working on this project
> Look at the extreme left side of the schematics.
> I paint leg 1 with "white correction fluid" and let it dry.
> leg 1 connect to red PIN of a digital meter and leg 2 give 75.5 ohm
> leg 1 connect to red PIN of a digital meter and leg 3 give 73.9 ohm
> leg 1 connect to red PIN of a digital meter and leg 4 give 74.2 ohm
> leg 1 connect to red PIN of a digital meter and leg 5 give 73.5 ohm
At this point we "know" that leg 1 is the common leg.
> leg 2 connect to red PIN of a digital meter and leg 3 give 147.2 ohm
> leg 2 connect to red PIN of a digital meter and leg 4 give 147.1 ohm +/-
> leg 3 connect to red PIN of a digital meter and leg 4 give 147.1 ohm +/-
> leg 4 connect to red PIN of a digital meter and leg 5 give 147.1 ohm +/-
Are these measurements made with the motor soldered into the circuit or with
just the motor alone. As they don't sound right to me. It seems like you
have a short somewhere. Each coil is approx 75 ohms (same as my experience
with floppy steppers), but only two pairs of legs should give you approx
150 ohms resistance. The other two pairs should be infinite resistance.
For *example* the resistance between 2 and 4 would be approx 150 ohms, and
between 3 and 5 would be 150 ohms. However, 2 and 3 would be open
circuit(infinite resistance) and the same for 4 and 5.
> The components have already soldered. But "nothing moves" at all.
> I connected the max 232 according to this url
> Any help appreciated.
You have already identified the common lead, it is "leg 1". The trick now
will be to identify the correct sequence to drive the other leads.
Fortunately it's not as hard as it may seem. Connect the + lead of a 6V
battery to leg 1. Now touch the - lead of the battery to each of the other
leads. You should be able to quickly distinguish the order by trial and
error as the output shaft will turn the opposite way if you touch the wrong
leg. The floppy drive steppers I have played with contain one set of
reversed legs. IE the sequence is something like 2, 4, 3, 5 but I don't
As for the Max 232, an oscilloscope will tell you for sure if it's working.
From what you have described, it sounds like you may be expecting too much
to "just work" the first time you test it. Have you verified that your
program is indeed running and generating the sequence of driving pulses?
Make your project simpler by breaking it down into more managable parts.
First just try to get the stepper to turn by using manual connections.
Once you have that figured out, hook it to your driver and stimulate that
manualy. After that, get the micro to step the motor without expecting any
input from the serial port. Once that works you can worry about adding the
serial communications. This is just one way to approach the problem,
others may(will) have their own ideas. I like to work backwards.
Oscilloscopes are invaluable when debugging microcontrollers and firmware.
LED's can be your friends too. Just my 2cents.
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