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From: "Frank Bemelman"
Subject: Re: Stepper motor question
Date: Sun, 12 Jan 2003 15:08:17 +0100
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
Organization: EuroNet Internet
NNTP-Posting-Date: 12 Jan 2003 14:08:46 GMT
"Esoteric" schreef in bericht
> Hello all,
> This is my first time working with a stepper motor and related drive
> I am using an optical encoder w/ 360 pulses/rev to generate a quadrature
> waveforem (2 bit grey code). This signal goes through logic and a Step
> pulse & Direction are generated as outputs. These are fed into an Alegro
> 5804. The 5804 is set up for full step with option for one or two
> The motor is a 6 wire unipolar motor. 12V 75ohm
> The system works fine while turning the dial on the encoder. The issue is
> that if I turn the dial too fast the stepper motor stops rotating and
> "buzzes" until I slow the ecoder down again. This is regardless of one or
> two phase operation on the Alegro.
> The Alegro 5804 docs state that a minimum step input pulse width is 3us.
> get nowhere near that with manual rotation. This condition occurs with a
> step input of around 10ms as seen on my scope. So I have ruled that
> Is this motor resonance? What is causing this and how do I get rid of
> I do not need extreem speed on the motor. It is being used to manually
> control a butterfly valve on a propane fired foundry. The stepper motor
> geared down such that it requires about 1000 steps to go from open to
> closed, this was done to increase resolution on controlling the valve.
Your motor does not develop enough torque. Try increasing the 12V to 15V, to
see if it can go a bit faster. When you go faster, the windings get shorter
pulses. It takes a while before the current reaches a certain level, and
with short pulses the current drops. The result is that your torque drops
and drops, and when too low, the motor stops. You have to find a way to
increase the current, increasing the supply voltage is the only option.
Beware that at low speeds the current gets larger, and a too high supply
voltage may overheat the motor.
Unipolar, 12V, 75ohm seems a rather small steppermotor. The UCN5804 is a
very simple stepperdriver. What you may need is a more sophisticated stepper
controller with current control (pwm) and a higher voltage. Possibly also
a motor with lower resistance windings.
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