View Full Version : Building a control system

Katie Reynolds
11-15-2001, 06:33 PM
Hey y'all. I'm trying to build a control system and I need to know the pulse period for the servos (HS-303)/speed controllers from last year's kit of parts. Any help would be greatly appreciated. Thanks :D

- Katie

Lloyd Burns
11-15-2001, 11:46 PM
The PWM output decides what the signal will be, but the output is repeated once per PBASIC loop.

Neutral is a 2ms positive pulse, and the pulse varies up to 1 ms either way (2ms, +/- 1 ms), although the Victors will handle less variation comfortably.

The PWM output reaches maximum (+/- 1ms)with numbers like 127 +/- 110 or so (ie 17 and 237), not the expected 0 and 254.


Joe Johnson
11-16-2001, 12:49 AM
If my memory server, I think the update rate of the Victors is 50hz (1 every 20 msecs). The interface is from the RC industry.

It is possible that the RC stretches the 20 msec updates to 25 msec, I but I am not sure.

It is my understanding that the width of the pulse is the main thing to hold not necessarily the time between pulses. As Lloyd said, I think that 2msec is Zero voltage and then you go +/- from there. I can't recall the exact format but is it something like 3msec is full foward and 1 msec is full reverse.

On thing that you should know is that the Pbasic loop that we all have to live with on the Innovation First controllers is not the same as the pulse rate for the Victors -- your Pbasic loop is allowed to miss 5 data packets (125 msec) without anything bad happening -- I am sure that the master CPU that drives the PWM outputs does not wait that long between pulses even if your Pbasic loop does take that much time.

Joe J.

Lloyd Burns
11-16-2001, 08:34 AM
You are, of course, correct Joe.:o I remember the figure of 16 ms from the previous (the clear top, pre-Black Top) controller outputs.

Lack of signal in the appropriate time window should cause the controller to go to neutral.