🚀 go-pugleaf

In article <848@earvax.UUCP> sbcd@earvax.UUCP (Scott Dynes) writes:
>I'm looking for help on the following: I would like to get/make an
>airspeed sensor for R/C models. This would require 1) a small
>accurate (and light!) pressure sensor that would run off a small set
>of batteries, and 2) a similarly small, light, low-power way to get
>the information down to earth. I'm thinking of having the output be
>a tone whose frequency is proportional to the airspeed. Does anyone
>know of such a system, or where to look for the individual pieces?
>Comments?? 

Sensors capable of detecting the small pressure differences you need tend to
be expensive and fragile.  You might look into surplus radiosondes which
already have the tone encoding (or alternative telemetry).

A much simpler approach would use a thermistor in its self-heating mode.  
The thermistor heats due to its current draw, but is cooled by the air flow.
To compensate for the change in ambient temperature, a bridge circuit using
two matched thermistors could be used.  A differential input op-amp stage
could then feed a simple voltage controlled oscillator.

Honeywell (Microswitch) makes a minature air flow sensor that should work
well in your application, but I have no idea as to its cost.  Good luck.
                                               Barry  WA4VZQ
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| |  / /        | |  Barry L. Ornitz  UUCP:..rutgers!rochester!kodak!ornitz
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