[simpits-tech] Simkits and Phidgets (Roy?)

[Matt Bailey]

On Sunday 20 February 2005 22:04, Chris Brace wrote:
> Matt,
>
> The Piher's on the simkits instruments circuit board can be read
> directly by a Phidget InterfaceKit's analogue input . I just rewired the
> end of the ribbon cable from the simkit instrument to get to the IFKit
> input. The problem with coding them is that Pihers's only go 350 degrees
> and so the simkits folks used two of them 180 degree's opposed to get
> the full 360 degrees needed. It mean that your code needs to read from
> one Phier until a certain point (say 270 degrees) and then switches to
> and reads from the other Piher. The other problem we found with them is
> that there is some drift in the actual position of the "null" zone in
> the Piher when you switch direction (CW vs. CCW). We ended up doing some
> adjustments in our software to take care of it but it’s a little
> troublesome at times.

	Hmmm, sounds a little quirky. I'm hoping the stepper controller will be 
supported by the Linux Phidgets API I'm using, some time. Steppers sound like 
a really good route to go. Still, good to hear I can read the Piher's from 
the Phidget IK. Sounds like another good excuse to get an IK. Maybe in a 
month or two when my funds have restabilized after the latest onslaught of 
sim-related goodies. :) Swapping Piher's in software should be no problem.

> The servo instrument are a snap, very simple. The only problem I don’t
> like about them is the jerky responses, solved with a smoothing routine
> in the software or better yet Chester was supposed to be working on
> smoothing in the firmware for the servo board themselves (Phidet
> advanced servo).

	Oh I'd planned on doing my own smoothing code anyway (I'll be doing graphics 
for glass instruments, so without the benefit of "natural" smoothing from 
servos I'll have to do some smoothing anyway). The sim I'm using (X-Plane) 
should typically be able to spit data out at 30hz at the least, or more 
during cruise or light scenery areas.......some interpolation should make 
this look presentable.
	I was actually somewhat surprised at the poor performance of the analog 
instruments on a relatively new Frasca ground trainer. I think they're using 
steppers for most stuff, but it's kinda horrid........noticeably notchy 
movement (the directional gyro, in particular).
	Thanks for the info.

	-Matt Bailey