[simpits-tech] Wiring of POT and EPL

[Martin Ingold]

Hummm. Ok well I really don't understand that much about elecs. But I'm _very_ happy to
NOT need a 400Hz signal to drive ANY of the instruments that have synchros in them, and
as mentioned, there are quite a few of them. While there might be a chip that generates
400Hz out of DC, none of the instruments have any of those in.
Oh and yep, the 324 Chip in the pic is a quad Op-Amp.
Anyway I'll leave it at this here :-)

Martin

Jim S wrote:

> At 28-2-03 23:23, you wrote:
> > > Ok, the synchro isn't using the DC, the circuit board is.  The sine/cosine
> > > signal *must* be AC for the synchro to resolve.  The only time you'll use
> > > DC for sine/cosine is in an air-core motor.  A synchro is a six wire
> > > device, an air-core motor is a 4 wire device.  I don't know what tricks
> > > Malwin is doing, but I've never seen a _real_ synchro function on DC.
> >
> >Well yes.... but I'm sure you can tell me where on that circuit they make
> >up the 400Hz
> >:-) Believe me Gene... it's like this with all the other Synchros I have
> >in instruments
> >too... no 400Hz.... Like I said I don't know how they do it, but they _DO_
> >it somehow....
> >
> >Martin
>
> A quick observation here might clarify matters. I looked at the picture and
> the key
> is in some of the circuitry that can be seen in the lower right part. The
> integrated
> circuit (blak thing with lots of legs for those who don't know) with the
> number 324
> on it is actually a quad operational amplifier. First, remember that the
> instrument
> is only the display device to the pilot. The sensors for what is being
> displayed on
> most of the instruments are elsewhere, and it is the signal from these sensors
> that is transmitted to the instrument. The most reliable way to send an
> accurate
> positional type signal in an aircraft is by the use of the symchro-resolver
> technique.
> There are two possibilitirs in the instrument shown.
>
> 1- in an instrument that only needs to drive a pointer or something of
> similar low
>     mass, the RX type synchro/resolver will receive a three phase AC signal
> PLUS
>     a reference signal (also AC at the same frequency) from the TX
> synchro/resolver
>     in the sensor device.
>
> 2- in an instrument that has a reasonable mass to move, a DC servo/gearing
> system
>      is used to drive the heavy components and the synchr/resolver is
> driven as part of
>      the servo feedback loop (similar to the pot in a R/C servo, but
> continuous rotation).
>      The operational amplifier seen in the picture is probably being used
> to boost the
>      weak RX synchro/resolver signal so that it can be used to accurately
> determine
>      the null-point for the main DC driving servo.
>
> Now with any luck, I have completely lost most of you, but believe me, the
> 400Hz AC
> signal IS being used. If anyone really wants to know how these things work,
> I can point
> them to some URLs that give a full treatise on the subject.
>
> Sorry for the lengthy input, but I could see a couple of you coming to
> blows over this.
>
> BTW, in the simulator systems that these instruments come from, the AC
> signals are
> generated by the expensive chips mentioned earlier. You just dont get given
> that part
> of the system when you buy the instrument.
>
> Jim.
>
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