Re: [CAD_CAM_EDM_DRO] Want some help about L297 chip

The data sheet shows a 22k and a 3.3nf (0.0033uf) capacitor. So that
should be a good starting point. That's what I'm using on my drivers,
and they work fine. (I'm using L298 drivers.)

Remember to use non-inductive sense resistors. These can be high-dollar
items in high wattages, so I used smaller wattage, less expensive ones
in parallel.

Data sheets for your L297s can be found here:
http://www.micromouse.co.uk/datasheets/
or at http://www.st.com

In particular, the Application Notes sections in the Data Sheets give
you some good starting points.

I assume since you're using four transistors that you're driving a
unipolar motor?

Regards,
JJ

On Monday, Oct 20, 2003, at 16:38 US/Eastern, Harvey White wrote:

> On Mon, 20 Oct 2003 00:14:31 -0500, you wrote:
>
>>
>>
>> yours_salman2002 wrote:
>>
>>> Hello users
>>> I am using L297 in my project for first time,therefore i
>>> want some help.I want to set it's chopping frequency to 20Khz so
>>> which values should be used for resistor and capacitor?
>>> I see its formula but i can't solves it :( .
>>> another thing is i use four IRF540 mosfets with L297 and i set L297
>>> chopper mode to phase type not (INH)type so did it works with 8AMP
>>> stepper motor? also i don't uses INH1 INH2 outputs but i use sense
>>> inputs.
>>>
>>>
>> I don't think you can set the chopping frequency that way. It
>> depends on
>> the inductance of the motor winding, the power supply voltage, and the
>> hysteresis of the current sensing amp.
>
> This is not my understanding of the way it works. The 297 can be
> driven by an external clock signal for chopping, so that would rule
> the frequency setting by motor inductance, voltage, and hysteresis
> out.
>
> However, the inductance, supply voltage, and hysteresis will have an
> effect on the current rise rate in the motor windings, and the
> ultimate current reached in the motor windings. You can make a very
> valid argument that the chopping frequency can be set so high that the
> motor will not easily reach full current in the amount of time
> allowed.
>
> the formula gives f = 1/(0.69 * R * C) .
>
> IF R is in ohms, C in farads, f will be in hertz.
>
> R in K ohms, C in microfarads, F will be in Khz.
>
> R must be at least 10000 ohms.
>
> Harvey
>
>
>>
>> Jon
>>
>
>
>
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