Re: L297/298's

You probably need more voltage. 12Vdc is nothing, for best results
gekodrives recomends about 25X the name plate voltage so for 3.2
volts you need about 80 volts. But you will reach the limit of the
L297/L298 before that. They may be rated for 40VDC or less. You
should see a big differance with just 24Vdc supplies.

--- In CAD_CAM_EDM_DRO@egroups.com, "Ian Wright" <Ian@i...> wrote:
> Hi,
>
> I've just built up a driver board based on the L297/298 chips and
I'm a bit
> disappointed at the maximum motor speed I seem to be able to get
from it - I
> managed 300 rpm with one motor and only 200 with another. The
motors are, I
> believe, 3.2 volt, and 1.4 and 0.8 amp respectively (the 0.8 amp
one went
> slowest) and I was driving them in half step mode from a 12 volt
3amp supply
> (L297 was set at motor's rated current output).
>
> On the machine I'm building with a 1:5 reduction driving a 1mm pitch
> leadscrew, the fastest equates to about 60mm or 2.5" per minute! -
a bit
> slower than you all seem to talk about!! That, of course, is also
the
> fastest I could expect - in G00 mode. Whilst I'm not too bothered
about
> speed, I wondered what typical speeds you were getting from
L297/298 driver
> boards and consequently whether mine are performing as well as I
might
> expect.
>
> In this test I was pulsing the step input with a 555-based
oscillator and
> the motors ran really cleanly with plenly of torque up to the
maximum speed
> I got and then suddenly stopped and sat there buzzing loudly.
>
> Ian
> --
> Ian W. Wright
> Sheffield UK