Re: Axis Stall Problems

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Paul Kelly" <tech@c...> wrote:

>
> How quick is your current control loop?
> The 16 series A2D converters have big input caps and its tricky to scan
> multiple inputs quickly. A 297 IC is a cheap thing....

The microcontroller appears to be taking samples at 40KHz.
Split between both axes, that is 20KHz sample rate per
axis.

The reason for choosing a PIC16F676 is two fold.

1) They are even cheaper than an L297 which has gotten
kind of pricy. The L297 is $5-$7 and the 'F676 is
about a $1.50. Mind you if the sample rate is the
problem, I'll gladly pay for the L297.

2) Also, with the 'F676 I have the opportunity to
do a microstepping drive. The L297 is limited as
to what kind of drive it supports.

What sort of chop rate should I be looking at for an L298?

[snippage]

> The chopper is implemented using a dedicated Microchip
> PIC16F676 microcontroller (one for each axis) running
> at 20MHz where a couple of A/D lines are used to measure
> the current flowing through each L298 H-Bridge. Each
> axis is being sampled at approximately 20KHz. If the
> current is too high, I turn the H-Bridge off and if
> the current is too low, I turn it on.

[snippage]

-Wayne