burning question - HSI?

[Leo Bodnar]

Question, Why not write a code and use the stock internals driven by PIC or or other interface. I think it would be easier to do this electronically and code versus mechanical?

Answer, Typical HSI uses galvos for flags and needle but synchros for knobs position sensing and driving the mechanical dial. Galvos can work from a regular DAC signal. But each synchro has a rotor coil and three stator coils that usually designed to work with 400Hz AC.
To use syncrho as a motor you have to feed rotor with a 400Hz sinewave and supply 3-phase sinewaves to three stator coils with shifted phase in relation to the rotor. This is hardly a trivial task. To use synchro as a position sensor one needs to supply 400Hz AC to rotor and simultaneously sample outputs of three stator phases. Then resolve the rotor position through vector algebra calculus.

By the way I have a 737 HSI that I intend to drive without any internal modifications. It has 9 synchros and 6 galvos. It is a pet project of mine so moves very slowly (but successfully) so far.

Good luck with your progress, Scott! It looks very impressive so far.

[cscotthendry]

Leo:

Thanks for the encouragement. Lately, I've neglected the poor HSI in favor of flying. I PROMISE I'll return to it soon and get it finished...Honest.

In the mean time.. keep us posted on your progress with the real HSI.

[Leo Bodnar]

No pressure Scott but you've gone too far to stop now!

I have found that my HSI uses an induction AC motor (skewed squirrel cage type) to drive the compass card (and everything else with it.)
It has 5 windings - I guess few of them are for tacho purposes... But we will get there!

[lencoo12]

Check out simkits (www.simkits.com). They don't have a HSI (yet) but talk to them maybe they have a solution.

Using Easy Guage you can program your own HSI for FS9. I've heard they are working on a new version that allows you to create guages for FSX also but I've no more info on that.

[jan_eddh]

Yippieh, just got a reasonable priced wrecked KI525A on e..y, I just hope I can get this to work without too many internal modifications. After I have it in hands I probably pop up with zillions of questions

[dc8flightdeck]

Tony used a real HSI in his F-4 Phantom sim. Video is here. http://www.youtube.com/watch?v=bS7kWIT3fKo

He used 400Hz AC to power sychro senders that are wired to the HSI synchro receivers. He opened some simkits instruments (Gyro Compass and NAV1) and uses their servos to spin the synchro senders.

The needles are conrolled by pots that are also linked directly to servos.

One major complication with using real instruments is the different approach by each manufacturer to make their intstruments. They may look very much the same on the outside, but often work very different from each other on the inside.

[Leo Bodnar]

Fascinating video!

Any hint where the jerky movement comes from - simulator, servos, mechanics or synchros?

Synchros are low torque devices - they are usually used as feedback senders and to drive light stuff like needles as receivers. Typically HSI card or ADI ball would have a geared DC or AC motor to create movement and then a synchro or resolver in a feedback loop. Interesting how Tony got around that. I assume he does not use feedback synchros to drive the mechanics.

Cheers
Leo

[dc8flightdeck]

Fascinating video!

Any hint where the jerky movement comes from - simulator, servos, mechanics or synchros?

Synchros are low torque devices - they are usually used as feedback senders and to drive light stuff like needles as receivers. Typically HSI card or ADI ball would have a geared DC or AC motor to create movement and then a synchro or resolver in a feedback loop. Interesting how Tony got around that. I assume he does not use feedback synchros to drive the mechanics.

Cheers
Leo

In this case the jerky movement comes from the servo. Airline instruments dampen out the signal and makes for very smooth movement. However aerobatic instuments are very sensitive and and dont dampen out rapid movements. Check out the video on my 737 webpage and you will see how smooth the ADI runs compared to the Phantom's ADI
http://blueangel.site90.net/1_7_737-200.html
For the 737 ADI we had to use signal amplifiers and it was a very involved project.

These units in Tony's F-4 have synchro receivers inside them that drive the motor's position. Normally a remote gyro fitted with synchro senders would feed the ADI or HSI with synchro signals. Instead of a gyro he used servos to spin synchro senders. The motors are provided with power on seperate pins.

I happen to work on gyros for the ADI on T-34's and they operate bassically the same as a Phantom ADI with synchro senders built directly into the remote gyro unit.

Of cource modifying a ADI, HSI, or DG the has a gyro mounted directly in the can rather than mounted as a remote unit in a completely different project.

My F-4 Phantom sim is loaded with sychro driven engine instruments, no motors used in the loop at all which is nice. I just have to take the time to get them working.

[MrProach]

Nice! Coincidentally I am finishing the project to drive Sperry HZ6 ADI from dedicated controller that just plugs over two connectors on the back an needs no internal modifications. I'll post some photos later.
This ADI uses 2 phase AC motor generators to drive the axes.

These units in Tony's F-4 have synchro receivers inside them that drive the motor's position.

OK, I see what you mean. The gyro computer usually sends the gyro position into the ADI's differential resolver that outputs the difference signal that is fed into a servo amplifier that generates motor control signal that is fed back into an ADI axis drive motor.

[dc8flightdeck]

OK, I see what you mean. The gyro computer usually sends the gyro position into the ADI's differential resolver that outputs the difference signal that is fed into a servo amplifier that generates motor control signal that is fed back into an ADI axis drive motor.

Actually, on the ADI the gyro unit is connected directly(mechanically) to a synchro sender, there is no computer input involved. Each synchro is wired directly (from a remote gyro box) to a syncro reciever inside the ADI. From there it is fed to the ADI axis drive motor. Its a simple straight forward system.

Im not clear how he connected feedback for HSI heading signals. He would have to somehow mechanically move the simkits phir(SP?) sensors.