[simpits-tech] Conversion of electrical gauges

Thu Apr 14 14:53:59 PDT 2005

Now this is good stuff.  I've been reading up on synchros and understand
them yet don't really understand them well enough to drive them.  The
principles I got, the applications allude me for the time being.  Mike
Powell been helping me with this.

The innards of the meter pretty much supply all the juice it needs, I just
need to supply it a signal now.  We suspect there is some sort of other
synchro that is physically interactive with the fuel flow and thus sends the
signal to this meter.  I just have to turn the digital number within Falcon
4 to an analog signal withing the fuel flow meter.

Oh, and what is a pll and how do I build one?

Jay

-----Original Message-----
From: simpits-tech-bounces at simpits.org
[mailto:simpits-tech-bounces at simpits.org] On Behalf Of
Phoenix2000 at phoenixcomm.net
Sent: Friday, April 15, 2005 9:58 AM
To: Simulator Cockpit tech list
Subject: Re: [simpits-tech] Conversion of electrical gauges

Hi Joseph
If I remember I tried to use the 60 Hz stuff but it is too lossy as its 
the wrong impedance....
and yes..
on the conversion... with out all the math... here it is... (college paper)
1. you need 400 Hz 3 phase supply this has to be really clean but you 
will need to make this a digital system and have your out puts 120 deg, 
out of phase.. These go to the 3 phase stator wires.
2. then you need to build an 400 Hz pll (phase lock loop against the 
phase 0.
3. when this is done your almost there...
4. now you have to change the phase of this phase to any arbitrary phase 
0 - 359 deg..  almost like fm but not..
1 bit  360
2 bits 180
3 bits  90
4 bits  45
5 bits  22.5
6 bits  11.25
7 bits   5.625
8 bits   2.8125
9 bits   1.40625
10 bits   .0703125
11 bits   .03515625
So with a 8 bit converter you should resolve to 1.5~ deg or so... a 
needles width...
5. drive this phase to your stator. and ta da...

FINS just remember that a syncro receiver is just like a motor... but it 
just doest drive in one direction all the time but you can 'direct' it 
just like a servo, but it uses a lot less power, and by increasing your 
conversion to lets say 12 bits  you get 0.1758125 deg of movement....
Happy Landings.

Joseph Fagner wrote:

>Why 400 hz only on step up/down transformers?  You can use a 60hz
>transformer to step up/down 400hz power but not the other way around. Is
>there a noise issue or something?  Also, what did you convert and how did
>you feed it signals?  Right now I'm working on getting an F-16 fuel flow
>meter working.  This baby has a built in transformer to step down
115v/400hz
>to 26v/400hz.  The problem I'm having is trying to drive the synchro
inside.
>I really need a Digtal to synchro converter, but they seem a bit tough to
>find.  Did you build a circuit that essentially converts the digital signal
>to an analog one?
>
>Jay
>
>-----Original Message-----
>From: simpits-tech-bounces at simpits.org
>[mailto:simpits-tech-bounces at simpits.org] On Behalf Of
>Phoenix2000 at phoenixcomm.net
>Sent: Friday, April 15, 2005 8:54 AM
>To: Simulator Cockpit tech list
>Subject: Re: [simpits-tech] Conversion of electrical gauges
>
>Hi Guys,
>You can use the 400 Hz stuff if you just build or get your self a 400 Hz 
>generator.. I hacked one together a more than a few years ago, so I dont 
>have the print for it any more.. but its not hard
>as you dont need  alot of power (ie Amps).
>1. You need a stable 400 Hz single phase generator. DONT use 74X04 in a 
>feed back loop as you will get a square wave and that wont work, It has 
>to be ANALOG.
>2. in the real world 26volts should work for 80/90% of your stuff.
>3. to get the current go through a Audio Amp (class C or AB) you will 
>have to change the output impeadance as 8 ohms will not work..
>4. OR if you are lazy.....buy a cheep 400 Hz gen and drive it will 1/2 
>horse motor.....
>and use step up/down transformers..(400 Hz only)
>
>Ta Da ...
>Happy Landings
>Cris Harrison
>www.phoenixcomm.net/~phnx2000/sim
>btw I will try and post an article to my site and this site when i find 
>the info....
>
>Gene Buckle wrote:
>
>  
>
>>Matt Bailey wrote:
>>
>>    
>>
>>>Howdy,
>>>
>>>  I occasionally see stuff like electronic tachs, altimeters, etc on 
>>>ebay. I know small systems instruments like EGT, oil pressure, etc as 
>>>seen on light planes, typically use air core motors, but what about 
>>>the big stuff (especially altimeters and other instruments with lots 
>>>of travel)? Judging by the connectors on one tachometer I see, I 
>>>assume it's a digital connection....sending data and not just a 
>>>simple voltage or something?
>>>
>>>  I'm about ready to start working on some Phidgets instruments using 
>>>servos, but I also want to look at other solutions (I'm still not 
>>>sure what I'm going to do about the altimeter.....Pihers sound 
>>>troublesome).
>>>      
>>>
>>Matt, you really need to buy Mike Powell's book on building sim 
>>instruments.  It's a goldmine of data and it'll even solve your 
>>altimeter problem.
>>
>>g.
>>
>>
>>    
>>
>
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>Thanks!
>
>  
>

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