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From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: Help please: Stepper wiring info needed
Date: Sat, 02 Nov 2002 19:36:23 GMT
NNTP-Posting-Date: Sat, 02 Nov 2002 11:36:23 PST
> In article , JB wrote:
> >I have a stepper from an old 5 1/4" floppy which I'm trying to find specs
> >It's a Berger-Lahr 540056-002, 4-wire device.
> >I need the voltage and current rating for this beast.
> >thanks in advance,
> 5 1/4" drives were generally stepped pretty slowly, with simple
> drive circuits. I guess your 4-wire stepper has three coils with a
> common terminal. A current was fed into one of the coils at any time.
> Typically there was a resistor from the 12V supply to the common, and
> then one of the three coil connections was grounded by selecting one
> of three transistors (one connected to each coil).
> If you still have the PCB from it, trace out a little of the circuit
> to find the resistor value, this then tells you the current they used.
> You can make an educated guess at the max continuous current rating
> by measuring the DC coil resistance, then P = I * I * R.
> 1 watt is maybe a reasonable maximum power to dissipate in it.
Most 4 wire steppers have exactly two coils and no common. They are
nearly identical to 6 wire steppers but the coils are not center tapped.
IC drivers for these are as common as grass but I don't have a part
number handy as I don't have my latest schematics for this at home. I'm
using a Motorola part that supports both half step and full step modes.
The important control lines are direction and step. Step is edge
detected. There are microstep controller chips available for these
motors. I think National may have one and quite possibly ST. The 4 wire
motors are generally driven with a pair of "H" drivers. Rohm offers
these combined with two transconductance power drivers and in other
power combinations but these chips seem to be hard to get.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons firstname.lastname@example.org
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