Xref: utzoo sci.electronics:4384 rec.models.rc:1105 Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ukma!rutgers!sunybcs!kitty!larry From: larry@kitty.UUCP (Larry Lippman) Newsgroups: sci.electronics,rec.models.rc Subject: Re: pressure transducers Summary: Airspeed telemetry possible, but not trivial effort... Keywords: airspeed, R/C models Message-ID: <2810@kitty.UUCP> Date: 5 Dec 88 06:13:28 GMT References: <848@earvax.UUCP> Distribution: na Organization: Recognition Research Corp., Clarence, NY Lines: 37 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? As you are no doubt aware, airspeed requires differential measurement (i.e., pitot tube), and therefore requires a differential pressure transducer. I'm afraid that I don't know about speeds of model aircraft, but "big aircraft" will provide a pitot differential pressure of 0.17 in-Hg (0.0835 psi) at 60 knots (the lowest airspeed for which I know a value). A model aircraft application will require a small and lightweight pressure transducer having some rather respectable sensitivity (as comparared to most other pressure transducers) - so you will not have much to choose from in an affordable price range. However, it just so happens that I have a catalog from SenSym (Sunnyvale, CA, 408/744-1500) on my desk. It appears that their P/N SCX01DN temperature compensated monolithic transducer will do the trick, and it carries a small quantity price of $ 49.50. You will have to provide a bridge-type signal conditioning circuit since this transducer has a sensitivity of 18 mv/psi, and you will have to exercise some care in circuit design to prevent RFI/EMI from the engine magneto. For telemtry, the simplest method is through the use of FM/FM telemetry; i.e., a V-F converter to modulate a transmitter, and a F-V converter connected to an appropriate FM receiver. More exact circuit details would be difficult to provide over the Net, but hopefully I have steered you in the right direction. <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {att|hplabs|mtune|utzoo|uunet}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"