I bought a real airliner altimeter some days ago in eBay and I just received it. The idea is, as I did with the HSI, convert it for use in the simulator with my master controller.

 

After disassembly I noticed this is not going to be an easy task. The altimeter is dated 1973, and it's an all-analog construction.

It has a DC motor and *a lot* of angular position sensors, called synchros. It's the same construction as the HSI has, and they are not easy to interface with.

 

The synchos are transformers, where the primary is stationary and the secondary rotates. Actually you have 3 secondaries, and, applying a sin wave to the primary, and measuring phase and amplitude on the secondaries, you can deduct the angular position.

 I wrote code for a PIC18 to use the synchro in the HSI, and I ran out of CPU power just monitoring one synchro. For this instrument,I will need to measure about 6 of them. The altimeter is built using a DC motor and a lot of synchros, with different demultiplications.

Looking at the value of the synchros, you can deduct the altitude the instrument is indicating.

 

I will post any progress here, but I guess this is a good candidate for using one of the dsPIC I have around.

 

These are the pictures of the dissasembled altimeter:

 

< Prev   Next >

Last Updated ( Monday, 08 June 2009 08:26 )