Using an Non First Microcontroller with Victor 884 Motor Controller

[Ether]

Originally Posted by electroken

The PIC output is sourcing 10mA to the one Victor 883 I measured. That's a reasonable input current for the optoisolators I'm used to. I'm pretty sure (but not certain) that the 883, 884, and Talon have optoisolators at the PWM input.

10 ma should be more than adequate. How did you measure that?

Your circuit should work with the Jag. You may not get full output (see Al's post) because the Jags want a wider range on the pulse width, but it should work... Unless, perhaps, the Jag's don't like the 4 ms period. If had a Jag here I'd test it at 4ms.

[electroken]

Originally Posted by Ether

10 ma should be more than adequate. How did you measure that?

Your circuit should work with the Jag. You may not get full output (see Al's post) because the Jags want a wider range on the pulse width, but it should work... Unless, perhaps, the Jag's don't like the 4 ms period. If had a Jag here I'd test it at 4ms.

The input current was derived from the voltage across the 270 ohm resistor, measured with a o'scope.

In all honesty, I didn't spend too much time troubleshooting the Jag. We have plenty of non-legal 883s for our test boxes.

[Ether]

Originally Posted by electroken

The input current was derived from the voltage across the 270 ohm resistor, measured with a o'scope.

That's pretty definitive :-)

Since I don't have a scope, I set the pulse width equal to the period and measure it with a cheap digital multimeter.

[Joe Ross]

Originally Posted by Ether

Your circuit should work with the Jag. You may not get full output (see Al's post) because the Jags want a wider range on the pulse width, but it should work... Unless, perhaps, the Jag's don't like the 4 ms period. If had a Jag here I'd test it at 4ms.

The Jaguar datasheet says 5.0125 ms minimum period.

[Ether]

Originally Posted by Joe Ross

The Jaguar datasheet says 5.0125 ms minimum period.

Well there ya go :-)

[apalrd]

Originally Posted by Joe Ross

The Jaguar datasheet says 5.0125 ms minimum period.

I noticed while working with the low-level FPGA interface in LabVIEW that the DIO loop on the FPGA basically cycles every 5.05ms. In this time, it generates a pulse for every PWM that isn't being skipped (because it skips 5.05ms iterations to get 10.1ms or 20.2ms pulse periods) and it shifts out all of the relay outputs at that same interval.

I wondered why it was 5.05 and not 5.00ms, this must be why...

[Ether]

Originally Posted by apalrd

...I wondered why it was 5.05 and not 5.00ms, this must be why...

I'm probably missing something obvious here... why does this explain the 5.05 period?

[apalrd]

The Jaguar spec wants 5.0125ms or greater period, according to Joe.

5ms would be a nice round number of milliseconds to use for timing the DIO loop. It's not 5ms, it's 5.05ms, which is clearly intentional because the timing is determined (in LabVIEW at least) by multiplying/dividing a bunch of things together, one of which is a 5.05 double-precision float constant. Even if it was the nearest round number, since they used a float it would have to round when converting to integer later in the math anyway since the period has to be a whole number of ticks, which itself is a whole number of 40mhz clock cycles.

[Ether]

Originally Posted by apalrd

The Jaguar spec wants 5.0125ms or greater period, according to Joe.

OK. The pronoun "this" was throwing me off. I thought it was referring to something in your preceding paragraph.

Anyway, FWIW I ran a couple of Jags for a couple of days at 5.000 ms period and never noticed a problem.