Return-Path: X-Spam-DCC: paranoid 1356; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, HTML_30_40,HTML_MESSAGE autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id t9VEmLSE011915 for ; Sat, 31 Oct 2015 15:48:21 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ZsXOO-0004Yi-8S for rs_out_1@blacksheep.org; Sat, 31 Oct 2015 14:44:28 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ZsXON-0004YZ-UT for rsgb_lf_group@blacksheep.org; Sat, 31 Oct 2015 14:44:27 +0000 Received: from mail-wm0-f41.google.com ([74.125.82.41]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.86) (envelope-from ) id 1ZsXNK-0002J2-PC for rsgb_lf_group@blacksheep.org; Sat, 31 Oct 2015 14:44:26 +0000 Received: by wmff134 with SMTP id f134so29905172wmf.1 for ; Sat, 31 Oct 2015 07:43:02 -0700 (PDT) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=+IZUK95ZiWHs2u66lKxrWYjD586IrsfGJp3Krhsb5lE=; b=0qrQLrqM0gSTqfnmghzZM/lWNx3Wemw9HrCbVhHH23/mCorUERkLIYhNR63RK5CRLu tRjBcZav1WMjo7OKA5Yq2GLsmiRoNFbZgYVNiskERwTvzVM9Lzfa5abUF+/EYJ2v2nmM VPywrfOxf+q89GVVzcp9xjh+QkETpnkuA+95NM1jDg2BTCDd9vKX/WEdEOE6n1cnjl6c IdjnOfotIKrzPFUOgNY06fQKbTVIA5uukPcvA5S3xYdGr3omJpQ7GXL47PU8F4DyTUJp KXWcNMkJujCKYbHxx6DoXyEKeJv/MZEsSvh2cdohVFxTVi+heEzVSYOzqm/L3MwmV14Q drSQ== MIME-Version: 1.0 X-Received: by 10.28.174.195 with SMTP id x186mr4102879wme.87.1446302582841; Sat, 31 Oct 2015 07:43:02 -0700 (PDT) Received: by 10.28.183.139 with HTTP; Sat, 31 Oct 2015 07:43:02 -0700 (PDT) In-Reply-To: <984267409.20151031132006@chriswilson.tv> References: <1981852865.20151017122027@chriswilson.tv> <1530BFEB-9BC2-4CA2-A7A3-338629A98202@me.com> <308511169.20151029202607@chriswilson.tv> <56328B1F.2080901@posteo.de> <12510142154.20151030112719@chriswilson.tv> <5633C6F8.4080807@posteo.de> <984267409.20151031132006@chriswilson.tv> Date: Sat, 31 Oct 2015 14:43:02 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org X-Scan-Signature: b4085bc26841e34d79a2f3beb8f287b1 Subject: Re: Re[2]: LF: Automatic variometer circuit Content-Type: multipart/alternative; boundary=001a11442822b028100523678f3b X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-Scanned-By: MIMEDefang 2.56 on 10.1.3.10 Status: O X-Status: X-Keywords: X-UID: 4726 --001a11442822b028100523678f3b Content-Type: text/plain; charset=UTF-8 Actually, looking again at the circuit again, it is not necessary to use an opamp in that position to define the mid rail for the comparator reference. Just two equal; value resistors and *one* electrolytic decoupling the junction to ground (Definitely not two caps to top and bottom in the original configuration shown ... think about it...) You only need an opamp to define a stiff mid rail voltage where there is likely to be any significant current draw. Or many stages need to be referenced to it - such as a multi stage filter. For single stage configurations, just two resistors and a bit of decoupling is enough Andy G4JNT On 31 October 2015 at 13:20, Chris Wilson wrote: > Hello Stefan, > > Friday, October 30, 2015 > > Thanks for the detailed info, and thanks to Andy `GNT for the info re > the caps. I will order the I/C's for this circuit, and I have ordered > a 2 RPM reduction drive motor and some micro switches for the limit > switches, so will be giving this a go! Much appreciated. > > > > Hi Chris, > > > My motor draws about 200 mA at 12V. It has about 1 round per 3 seconds i > > estimate. Costs are below 10 EUR. You will find something on ebay for > > example. > > I use end-switches in the construction BTW, see > > > https://dl.dropboxusercontent.com/u/19882028/LF/variometer%20end%20switches.jpg > > just to prevent the wind-up of the cable, antenna wire, coax (would > > sound like "crrrrrkftftftftftplingftftftftbuffftftftft...") > > > 73, Stefan > > > > > > > > > -- > Best regards, > Chris mailto:chris@chriswilson.tv > > > --001a11442822b028100523678f3b Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Actually, looking again at the circuit again, it is not ne= cessary to use an opamp in that position to define the mid rail for the com= parator reference. =C2=A0 =C2=A0Just two equal; value resistors and one<= /b> electrolytic decoupling the junction to ground (Definitely not two caps= to top and bottom in the original configuration shown ... think about it..= .) =C2=A0

You only need an opamp to define a stiff mid r= ail voltage where there is likely to be any significant current draw.=C2=A0= Or many stages need to be referenced to it - such as a multi stage filter.= =C2=A0 =C2=A0For single stage configurations, just two resistors and a bit= of decoupling is enough

Andy =C2=A0G4JNT
=

On 31 October 2015 at 13:20, Chris Wilson <chris@chriswilson.tv>= ; wrote:
Hello Stefan,

Friday, October 30, 2015

Thanks=C2=A0 for the detailed info, and thanks to Andy `GNT for the info re=
the=C2=A0 caps. I will order the I/C's for this circuit, and I have ord= ered
a=C2=A0 2=C2=A0 RPM=C2=A0 reduction=C2=A0 drive motor and some micro switch= es for the limit
switches, so will be giving this a go! Much appreciated.


> Hi Chris,

> My motor draws about 200 mA at 12V. It has about 1 round per 3 seconds= i
> estimate. Costs are below 10 EUR. You will find something on ebay for<= br> > example.
> I use end-switches in the construction BTW, see
> https://dl.dropb= oxusercontent.com/u/19882028/LF/variometer%20end%20switches.jpg
> just to prevent the wind-up of the cable, antenna wire, coax (would > sound like "crrrrrkftftftftftplingftftftftbuffftftftft...")<= br>
> 73, Stefan








--
Best regards,
=C2=A0Chris=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 mailto:chris@chriswilson.tv



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