So one of the things I really want to have for some added realism is the Whiskey Compass on the windscreen center post turning as the plane comes around.

So I had this idea for creating one.  With all of the parts for this....... it should be able to be done for under $60....... including the single Phidget servo controller, the servo, the mods to the servo, the car compass, and the housing. If I go for the four unit servo controller (want some other guages too later) the cost for the one part here goes down a tad.

So please take a look a the diagram I have drawn below... and tell me if this will work... or if it won't.  

Key to this idea is modifying the HS-322 for 360 degree rotation.  This servo is only about $10.00  .


Thanks.




best,

..................john

Sadly, no it won't work.

Modification to a servo to make it turn 360 degrees removes the feedback ability...the servo no longer knows where it is pointed.

What might work is to add a rotary encoder to the servo output. The encoder could pass the position back to the Phidget so that the system would know where the output was. I don't think that the programming exists in FS2Phidgets to use that feedback, but the guy who wrote it seems cool and might add the capability if asked nice.

I do like the idea of magnetically coupling the pices together...vary the distance slightly and you can get the typical "Whiskey Compass Hunt" and is lags behind and the oscillates and overswings a little bit.

For my own Whiskey compass I was thinking of gearing a standard servo output by 1:4...the output is then 360, plus a little bit of available over travel. The only hangup is that when rotating past end-of-travel points the servo would have to swing all the other way around.

I can live with that limitation...but if the software can be tweaked to allow your idea, well I'll go another way.

You're magnetic coupling concept gave me an idea...one which needs no servo at all...and no stepper motors.

What we need to do is create a large "air core" magnetic instrument. An air core instrument movement is capable of rotating the magnetic field around 360 degrees...and would over-ride the Earth's magnetic field at close range. The compass would think it was reading correctly...but we fool it. Feedback isn't needed...there's no way in the physical universe for the reading to get wrong in the first place once it's aligned!

I have to dig back into my books for EM field creation...but this is doable and would be very easy to have programmed into a FS2Phidget...only you would need the output from three channels of a digital output board or a dedicated controller...I'll have to see hwat I can figure out.

I had an idea that is useable in more places...and doesn't require handling the air-core driver circuits.

It also has a better chance of being implemented into FS2Phidgets...the basic function is useful for more than just FS. Thanks to SAto for mentioning optical interrupters...I knew there was an easier way to do what was required that I was forgetting.

Same exact setup as the original...except we add an optical encoder disk, an optical encoder and the encoder input to the mix. Using this system the system would basically use "dead-reckoning" based on known rotation rate and duration of rotation. The encoder disk/interrupter will allow the system to self-calibrate and to re-calibrate continuously as it rotates.



What the Encoder would like like. This has only 4 encoded positions...there is no reason it couldn't have even more:

$50!? I spent that much building my rudder pedals!

John, I have the solution! turn this into a full motion pit, then you wont have to do anything to the compass.  

LOL, I know.

Not a thing wrong with free stuff. Ive gotten all of my hard drives for free.

I think the "bobble" will be fairly noticeable...but with a fast servo it might not be too bad.

A Hitec 322 servo has a 60 deg travel time of .19 sec a 5V. Geared for 360 deg would load it up a bit...so make it .25/60 deg. You would need to gear it 5/1 (approx 80 degree servo travel would give you 400 deg total travel). Make the end rotation .05 sec/60 deg.

You might just be able to "lose" the compass for a moment, catching it as you come back around .3 seconds later. The real trick will be careful spacing of the magnet to override the compass... but allow it to get lost when wanted.

If that doesn't work there is a way to modify it so that it does:

Replace the bar magnet with a low powered electromagnet (hand wind one...it's easy). Power this magnet at all time except when crossing the 360 deg point. At 360 release the electro and apply power to a second magnet, a "holder". The holder hangs on to the compass until the servo swings back around and then releases it to the original magnet.

This is much more complex...and quite probably unnecessary. You should be able to build it the way you last described.

You can find gears here: http://www.servocity.com/html/gears___sprockets.html