Xref: utzoo rec.models.rc:1104 sci.electronics:4383 Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!rochester!kodak!ornitz From: ornitz@kodak.UUCP (barry ornitz) Newsgroups: rec.models.rc,sci.electronics Subject: Re: pressure transducers Summary: Alternative Approach Keywords: airspeed, R/C models,pressure sensors,thermistors Message-ID: <1508@kodak.UUCP> Date: 5 Dec 88 04:00:29 GMT References: <848@earvax.UUCP> Reply-To: ornitz@kodak.UUCP (barry ornitz) Followup-To: sci.electronics Distribution: na Organization: Eastman Kodak Co, Rochester, NY Lines: 32 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 ----------------- | ___ ________ | | | / / | | Barry L. Ornitz UUCP:..rutgers!rochester!kodak!ornitz | | / / | | Eastman Kodak Company | |< < K O D A K| | Eastman Chemicals Division Research Laboratories | | \ \ | | P. O. Box 1972 | |__\ \________| | Kingsport, TN 37662 615/229-4904 | | -----------------