[simpits-tech] Driving Synchros - Here is what I found...

[Marv De Beque]

Okay, I have done additional research and here is what I have found.

I have only contacted one company, but the best price for digital to 
synchro conversions is about $350 per channel.  Actually, the module 
costs $700, but it has two synchro channels.

Obviously, this is not very enticing to the wallet, so I will continue 
searching for better alternatives.

The problem is that synchros require some drive current and the D2S that 
this company sells are 16-bit high quality modules.  There is no way 
that you or I could tell the difference between 12 bits of resolution of 
16 bits (which is something like 0.005 degrees of resolution).  I would 
contend that 0.1 degrees of resolution is plenty for an analog gauge.

However, I do have another proposal.  I believe I can build a small 
microprocessor based board that will accept a serial data input with 12 
bits of precision that will produce two 12 bit precision analog outputs 
designed to drive a single 4-wire synchro.

A preliminary cost analysis puts the price of this interface at about 
$100, depending on the amount of drive current required.  This should 
work quite well for the simulation world.  The preliminary specs would 
be:

About 0.18 degrees of resolution.  That is, 12 bits minus 1 bit of noise 
for 11 bits or 2^11 which is 2048.  If you divide 360 by 2048 you get 
0.1758 degrees.  I think that amount of movement is fine enough for us 
regular guys and girls.

The other issue is latency.  There will be a small amount of time 
between when the digital number is received and when the value is 
translated to the synchro.  I would expect that latency to be under 10 
milliseconds.  I think that is plenty quick enough for us.

The input would be by serial port on the micro and you simply send it 
two 8-bit words preceded by some sort of header byte.  I would think 
that some sort of standard could be created that allows multiple boards 
to listen on the same serial line so you could simply output a 
continuous string of serial data that could be intercepted by the 
micro.  Each board could be "strapped" with an address using jumpers so 
you can assign a unique place in the data string to grab its data.

If there is enough interest in such a device I would consider building a 
test design and then having real PCBs made up and stuffed in quantity.

Marv

On Thursday, April 4, 2002, at 10:10 AM, Gene Buckle wrote:

>> WE are putting a synchro port on the product we are building.  I KNOW
>> that it doesn't cost $1,000!  However, let me find out more information
>> and I will let you know.
>>
> Well yeah, Honeywell is going to buy them by the hundreds, not 1 or two 
> at
> a time. :)
>
> g.
>
>> Still, even $100 per gauge isn't cheap and some of the gauges have
>> multiple synchros, too.
>>
>> Marv
>>
>> On Wednesday, April 3, 2002, at 10:04 PM, Gene Buckle wrote:
>>
>>>
>>>> There are chips available to do just that and I am told by one of our
>>>> hardware engineers that the cost is about $100.  I am sure there are
>>>> some odds and ends as far as support circuitry, but that would be
>>>> pennies compared to the converter chip.
>>>>
>>>> If you really want to know, I'll ask at work.
>>>>
>>>> Marv
>>>
>>> Marv, the last time I looked, it was $910.00 each for *one* 18 pin 
>>> dip.
>>>
>>> g.
>>>
>>>
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