X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.123] verified) by logan.com (CommuniGate Pro SMTP 5.3.11) with ESMTP id 4647279 for flyrotary@lancaironline.net; Sun, 19 Dec 2010 17:31:10 -0500 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.123; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=1.1 cv=Inhw+Jdt7z1D3BivGPfn2aw54OvUEJw5lAn/booRZkE= c=1 sm=0 a=XfJtRApuU7IA:10 a=rPkcCx1H5rrOSfN0dPC7kw==:17 a=hxVx0QqZEWFgl7tNQ8UA:9 a=dBeIsFrFh0unTH6Mbt2dSP50od8A:4 a=wPNLvfGTeEIA:10 a=aAR5LreKDFEC08Z3:21 a=LhUx5Fk8Aly0FK6K:21 a=pedpZTtsAAAA:8 a=Ia-xEzejAAAA:8 a=81B_xxnB9TXm-4he2p0A:9 a=FRdYhNzc3xsX_sUDrLwA:7 a=E9iMWePkrpwMl79XSOo8qyuXJgUA:4 a=eJojReuL3h0A:10 a=EzXvWhQp4_cA:10 a=rPkcCx1H5rrOSfN0dPC7kw==:117 X-Cloudmark-Score: 0 X-Originating-IP: 174.110.167.5 Received: from [174.110.167.5] ([174.110.167.5:56720] helo=EdPC) by cdptpa-oedge04.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id 20/45-13137-C878E0D4; Sun, 19 Dec 2010 22:30:36 +0000 Message-ID: <9E291B73C3B7453D9C9C73E4C8C96E60@EdPC> From: "Ed Anderson" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Cheap prop tach Date: Sun, 19 Dec 2010 17:30:35 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_01E6_01CB9FA2.71F151F0" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 This is a multi-part message in MIME format. ------=_NextPart_000_01E6_01CB9FA2.71F151F0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Well, it depends on a lot of things - there are about 3-4 different = basic schemes for producing an RPM reading from a signal source ranging = from a simple pulse intergration circuit which basically charges a = capacitor to a different voltage level depending on the average voltage = produced by the pulse train all the way to a microchip based on which = measure the interval between each pulse and gives you an (almost) = instantaneous rpm reading. Then the manner of display comes into play - a simple cheap voltage = meter could be used to display the charge on the capacitor and you = calibrate it for rpm - or there is a relative simple LED BAR graph that = displays the number of dots depending on rpm, to and LCD type read out, = etc. You could probably find something on the internet - it would just need = to handle 6 pulse/rev and whatever voltage the MT signal is. A suitable = 6 pulse/rev might be a bit harder to find than the more common 1 -4 = Pulse/rev , but they are probably out there. Ed From: Bill Bradburry=20 Sent: Sunday, December 19, 2010 5:12 PM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Cheap prop tach Ed, The MT electric prop has a prop speed pickup that senses 6 bolt heads = per revolution as they go by the sensor. How difficult/expensive would = it be to fabricate an LED readout that will give prop rpm that taps into = this signal line? =20 Bill B ------=_NextPart_000_01E6_01CB9FA2.71F151F0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Well, it depends on a lot of things - there are = about 3-4=20 different basic schemes for producing an RPM reading from a signal = source=20 ranging from a simple pulse intergration circuit which basically charges = a=20 capacitor to a different voltage level depending on the average voltage = produced=20 by the pulse train all the way  to a microchip based on which = measure the=20 interval between each pulse and gives you an (almost) instantaneous rpm=20 reading.
 
Then the manner of display comes into play - a = simple=20 cheap voltage meter could be used to display the charge on the capacitor = and you=20 calibrate it for rpm - or there is a relative simple LED BAR graph that = displays=20 the number of dots depending on rpm, to and LCD type read out, = etc.
 
You could probably find something on the = internet - it=20 would just need to handle 6 pulse/rev and whatever voltage the MT signal = is.  A suitable 6 pulse/rev might be a bit harder to find than the = more=20 common 1 -4 Pulse/rev , but they are probably out there.
 
 
 
Ed

From: Bill Bradburry
Sent: Sunday, December 19, 2010 5:12 PM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Cheap prop tach

Ed,

The MT electric prop has a = prop=20 speed pickup that senses 6 bolt heads per revolution as they go by the=20 sensor.  How difficult/expensive would it be to fabricate an LED = readout=20 that will give prop rpm that taps into this signal=20 line?

 

Bill=20 B

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