Re: Stepper controllers

Thanks Jon,

Sorry its taken a while to get back to you but the wife has just forced
me to endure the rigors of two weeks in the sun on Malta!

Ian

Jon Elson wrote:

>
> From: Jon Elson <jmelson@...>
>

> No, this is all wrong. You don't want to 'block voltage', you want to
> recirculate current. The inductance of the motor causes voltages to be
> produced when you abruptly try to stop the current. Generally, in the
> case of the resistor-fed unipolar stepper driver, you have a diode's anode
> at each end of the motor winding, (where the transistor also is connected)
> and the cathodes connect back to the motor's center tap. You can connect
> a small value resistor in series with the diode to allow the current in the
> motor winding to collapse faster.
>
> In your scheme, you need not worry about the diode's blocking capacity,
> you'd better worry about the motors' voltage capability. You could
> easily develop several hundred volts of flyback when the current is
> abruptly stopped, and it could arc over inside the motor.
>
> Jon
>
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Best wishes

Ian

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