Gyros + mixers= jitter

[rdresch]

I am involved in VTOL designs. Lots of issues with gyros. Ist when using gyros with a co-pilot servos freeze. Second when using gyros with mixers similar results. What are the rules when stacking devices? How can you tell which gyro will work with which mixer. Any way to know in advance? All the vtol guys have similar issues. I was hoping some of you here could educate those of us electronically deficient.

[red-panda]

Ive had various strange problems with gyros and mixers, resulting in servo jitter and odd outputs from the mixer, which I'm fairly certain is due to the devices taking different times to initialise. For example if the mixer were to initialise before the gyro (most likely scenario), the mixer will be looking for an input from the gyro before one is available and I would guess the result of trying to mix a valid pulse with none or garbage depends on the mixer firmware. I've done some tests powering up the system sequentially rx-gyros-mixers-servos and this seems to result in good behaviour, but for ease of actual use I've gone back to just plugging in the battery, and if I notice strange behavior simply unplugging and replugging till it behaves! In a similar vein I've found that some receivers do not like to have mixers on some outputs, although they'll drive a servo directly quite happily.

Chris

[mike50]

I suspect the problem is related to the fact that most radios (at least non-PCM radios) produce their output pulses in sequence. No two channels' outputs occur at the same time. Some mixing devices (such as the co-pilot) depend on this fact - they don't have to read two channels simultaneously. When the pulses come from two independent sources, such as a receiver and a gyro, there is no guarantee that the pulses for the channels being mixed won't overlap.

Mike

[rdresch]

Very helpfull posts, Thank you both. Still what is the solution for this?
Rudy