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Date: Thu, 23 Jan 2014 13:42:36 -0500
Message-ID: <CACPio-78NMn7Xi7JKZgPp0WtqVeq-F_E-HVbkLT5jHckPb0mjw@mail.gmail.com>
Subject: Re: [geda-user] Best way to measure RPMs
From: Nathan Stewart <therealnathanstewart AT gmail DOT com>
To: "geda-user AT delorie DOT com" <geda-user AT delorie DOT com>
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What I had in mind given the ferrous gear ring was something like Cherry's
VN101501, but it's pricier than I expected ($7.22/qty 1). It requires a
fixed permanent magnet on the other side of the gear tooth from the sensor.

A photo interrupter like Sharp GP1S58VJ100F is $0.93/qty 1 from DigiKey,
but typical current draw on the LED is 10-20mA. Not huge, particularly if
you're contributing to the electrical power generation, but enough to make
batteries a nuisance. (And if you a running a generator off that crank,
then there ya go - you already have your sensor elements built in.)


On Thu, Jan 23, 2014 at 9:33 AM, Dave Kerber <
dkerber AT warrenrogersassociates DOT com> wrote:

> I can hit 120 or slightly more with my legs and a light load, so I expect
> I could go higher with my arms.  That's with a shorter radius, though;
> 170mm crank arms.  I'd bet that if you allow up to 120-150rpm, you should
> be able to handle all but the most extreme cases.
>
>
>
> > -----Original Message-----
> > From: Rob Butts [mailto:r DOT butts2 AT gmail DOT com]
> > Sent: Wednesday, January 22, 2014 3:51 PM
> > To: geda-user AT delorie DOT com
> > Subject: Re: [geda-user] Best way to measure RPMs
> >
> > I was just looking at slot type photointerrupters.  I'd like
> > to have the option to take advantage of resolution too.  They
> > are cheap and I think will do what I need.
> >
> > The rpm range is a guess but 0 - maybe 60?  How fast can
> > someone pedal a hand bike with roughly a 9" handle radius?
> >
> >
> > On Wed, Jan 22, 2014 at 3:30 PM, Ed Simmons
> > <ed AT estechnical DOT co DOT uk> wrote:
> >
> >
> >       Do you care about resolution within a revolution?
> > Typically, for example on the front wheel of a motor bike,
> > you'd have a toothed wheel with one missing tooth as an index
> > pulse read by a hall effect sensor, equally simple is doing
> > the same thing with an optical setup. You can count 'normal'
> > pulses to get the resolution you need within an individual
> > turn and also look out for the longer pulse (or gap) caused
> > by the index notch.
> >
> >       If you only care about single revs, stick a magnet on
> > the shaft and have a reed switch to count revs.
> >
> >       HTH,
> >
> >       Ed
> >
> >
> >       On 22/01/14 20:23, Rob Butts wrote:
> >
> >
> >               The application is an arm bicycle where the
> > spinning shaft is connected to a handle on each end so with
> > no gearing the rpms will not be too high.  I don't have any
> > encoder yet and I can attach anything to the shaft.
> >
> >
> >               On Wed, Jan 22, 2014 at 3:13 PM, Nathan Stewart
> > <therealnathanstewart AT gmail DOT com> wrote:
> >
> >
> >                       That depends a lot on whats attached to
> > the shaft, how fast it's turning, and what's driving it.
> > Obvious solutions are encoder, interrupter (photo or magnetic
> > - ic engines typically use an inductive pickup on gear
> > teeth), or even counting pulses on the drive current. If you
> > already have an encoder for other purposes, that makes a lot
> > of sense. If you don't already have anything else that might
> > work, interrupter and divide by is probably the most direct
> > method. Sensing the driving forces can be a lot of things,
> > from stepper motor pulses to spark plug firing.
> >
> >
> >                       What's the application?
> >
> >
> >
> >
> >
> >                       On Wed, Jan 22, 2014 at 3:00 PM, Rob
> > Butts <r DOT butts2 AT gmail DOT com> wrote:
> >
> >
> >                               I have a shaft that I want to
> > measure the rpm of.  I'm looking for opinions on the best and
> > cheapest way.  The design is still in development phase so I
> > have freedom.
> >
> >                               Thanks
> >
> >
> >
> >
> >
> >
>

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<div dir=3D"ltr"><div>What I had in mind given the ferrous gear ring was so=
mething like Cherry&#39;s VN101501, but it&#39;s pricier than I expected ($=
7.22/qty 1). It requires a fixed permanent magnet on the other side of the =
gear tooth from the sensor. <br>
<br></div>A photo interrupter like Sharp GP1S58VJ100F is $0.93/qty 1 from D=
igiKey, but typical current draw on the LED is 10-20mA. Not huge, particula=
rly if you&#39;re contributing to the electrical power generation, but enou=
gh to make batteries a nuisance. (And if you a running a generator off that=
 crank, then there ya go - you already have your sensor elements built in.)=
<br>
</div><div class=3D"gmail_extra"><br><br><div class=3D"gmail_quote">On Thu,=
 Jan 23, 2014 at 9:33 AM, Dave Kerber <span dir=3D"ltr">&lt;<a href=3D"mail=
to:dkerber AT warrenrogersassociates DOT com" target=3D"_blank">dkerber AT warrenroge=
rsassociates.com</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">I can hit 120 or slightly more with my legs =
and a light load, so I expect<br>
I could go higher with my arms. =A0That&#39;s with a shorter radius, though=
;<br>
170mm crank arms. =A0I&#39;d bet that if you allow up to 120-150rpm, you sh=
ould<br>
be able to handle all but the most extreme cases.<br>
<div class=3D"im HOEnZb"><br>
<br>
<br>
&gt; -----Original Message-----<br>
&gt; From: Rob Butts [mailto:<a href=3D"mailto:r DOT butts2 AT gmail DOT com">r.butts2=
@gmail.com</a>]<br>
</div><div class=3D"HOEnZb"><div class=3D"h5">&gt; Sent: Wednesday, January=
 22, 2014 3:51 PM<br>
&gt; To: <a href=3D"mailto:geda-user AT delorie DOT com">geda-user AT delorie DOT com</a>=
<br>
&gt; Subject: Re: [geda-user] Best way to measure RPMs<br>
&gt;<br>
&gt; I was just looking at slot type photointerrupters. =A0I&#39;d like<br>
&gt; to have the option to take advantage of resolution too. =A0They<br>
&gt; are cheap and I think will do what I need.<br>
&gt;<br>
&gt; The rpm range is a guess but 0 - maybe 60? =A0How fast can<br>
&gt; someone pedal a hand bike with roughly a 9&quot; handle radius?<br>
&gt;<br>
&gt;<br>
&gt; On Wed, Jan 22, 2014 at 3:30 PM, Ed Simmons<br>
&gt; &lt;<a href=3D"mailto:ed AT estechnical DOT co DOT uk">ed AT estechnical DOT co DOT uk</a>&g=
t; wrote:<br>
&gt;<br>
&gt;<br>
&gt; =A0 =A0 =A0 Do you care about resolution within a revolution?<br>
&gt; Typically, for example on the front wheel of a motor bike,<br>
&gt; you&#39;d have a toothed wheel with one missing tooth as an index<br>
&gt; pulse read by a hall effect sensor, equally simple is doing<br>
&gt; the same thing with an optical setup. You can count &#39;normal&#39;<b=
r>
&gt; pulses to get the resolution you need within an individual<br>
&gt; turn and also look out for the longer pulse (or gap) caused<br>
&gt; by the index notch.<br>
&gt;<br>
&gt; =A0 =A0 =A0 If you only care about single revs, stick a magnet on<br>
&gt; the shaft and have a reed switch to count revs.<br>
&gt;<br>
&gt; =A0 =A0 =A0 HTH,<br>
&gt;<br>
&gt; =A0 =A0 =A0 Ed<br>
&gt;<br>
&gt;<br>
&gt; =A0 =A0 =A0 On 22/01/14 20:23, Rob Butts wrote:<br>
&gt;<br>
&gt;<br>
&gt; =A0 =A0 =A0 =A0 =A0 =A0 =A0 The application is an arm bicycle where th=
e<br>
&gt; spinning shaft is connected to a handle on each end so with<br>
&gt; no gearing the rpms will not be too high. =A0I don&#39;t have any<br>
&gt; encoder yet and I can attach anything to the shaft.<br>
&gt;<br>
&gt;<br>
&gt; =A0 =A0 =A0 =A0 =A0 =A0 =A0 On Wed, Jan 22, 2014 at 3:13 PM, Nathan St=
ewart<br>
&gt; &lt;<a href=3D"mailto:therealnathanstewart AT gmail DOT com">therealnathanste=
wart AT gmail DOT com</a>&gt; wrote:<br>
&gt;<br>
&gt;<br>
&gt; =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 That depends a lot on what=
s attached to<br>
&gt; the shaft, how fast it&#39;s turning, and what&#39;s driving it.<br>
&gt; Obvious solutions are encoder, interrupter (photo or magnetic<br>
&gt; - ic engines typically use an inductive pickup on gear<br>
&gt; teeth), or even counting pulses on the drive current. If you<br>
&gt; already have an encoder for other purposes, that makes a lot<br>
&gt; of sense. If you don&#39;t already have anything else that might<br>
&gt; work, interrupter and divide by is probably the most direct<br>
&gt; method. Sensing the driving forces can be a lot of things,<br>
&gt; from stepper motor pulses to spark plug firing.<br>
&gt;<br>
&gt;<br>
&gt; =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 What&#39;s the application=
?<br>
&gt;<br>
&gt;<br>
&gt;<br>
&gt;<br>
&gt;<br>
&gt; =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 On Wed, Jan 22, 2014 at 3:=
00 PM, Rob<br>
&gt; Butts &lt;<a href=3D"mailto:r DOT butts2 AT gmail DOT com">r DOT butts2 AT gmail DOT com</a>=
&gt; wrote:<br>
&gt;<br>
&gt;<br>
&gt; =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 I have a s=
haft that I want to<br>
&gt; measure the rpm of. =A0I&#39;m looking for opinions on the best and<br=
>
&gt; cheapest way. =A0The design is still in development phase so I<br>
&gt; have freedom.<br>
&gt;<br>
&gt; =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 Thanks<br>
&gt;<br>
&gt;<br>
&gt;<br>
&gt;<br>
&gt;<br>
&gt;<br>
</div></div></blockquote></div><br></div>

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