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Mail Archives: geda-user/2014/01/22/15:51:34

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Date: Wed, 22 Jan 2014 15:51:14 -0500
Message-ID: <CALSZ9gpGhxTwZtGZL+j_RKJaOcJz0GVC3u3-vu0zOwgvB5Apww@mail.gmail.com>
Subject: Re: [geda-user] Best way to measure RPMs
From: Rob Butts <r DOT butts2 AT gmail DOT com>
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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>I was just looking at slot type=A0photointerrupters.=
=A0 I&#39;d like to have the option=A0to take advantage of resolution too.=
=A0 They are cheap and I think will do what I need.</div><div>=A0</div><div=
>The rpm range is a guess but 0 - maybe 60?=A0 How fast can someone pedal a=
 hand bike with roughly a 9&quot; handle radius?</div>
</div><div class=3D"gmail_extra"><br><br><div class=3D"gmail_quote">On Wed,=
 Jan 22, 2014 at 3:30 PM, Ed Simmons <span dir=3D"ltr">&lt;<a href=3D"mailt=
o:ed AT estechnical DOT co DOT uk" target=3D"_blank">ed AT estechnical DOT co DOT uk</a>&gt;</spa=
n> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">
 =20
   =20
 =20
  <div text=3D"#000000" bgcolor=3D"#FFFFFF">
    <div>Do you care about resolution within a
      revolution? Typically, for example on the front wheel of a motor
      bike, you&#39;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 &#39;normal&#39;
      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.<br>
      <br>
      If you only care about single revs, stick a magnet on the shaft
      and have a reed switch to count revs.<br>
      <br>
      HTH, <br>
      <br>
      Ed<div><div class=3D"h5"><br>
      <br>
      On 22/01/14 20:23, Rob Butts wrote:<br>
    </div></div></div><div><div class=3D"h5">
    <blockquote type=3D"cite">
      <div dir=3D"ltr">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.=A0 I don&#39;t have any enco=
der
        yet and I can attach anything to the shaft.</div>
      <div class=3D"gmail_extra"><br>
        <br>
        <div class=3D"gmail_quote">On Wed, Jan 22, 2014 at 3:13 PM, Nathan
          Stewart <span dir=3D"ltr">&lt;<a href=3D"mailto:therealnathanstew=
art AT gmail DOT com" target=3D"_blank">therealnathanstewart AT gmail DOT com</a>&gt;</sp=
an>
          wrote:<br>
          <blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8=
ex;padding-left:1ex;border-left-color:rgb(204,204,204);border-left-width:1p=
x;border-left-style:solid">
            <div dir=3D"ltr">
              <div>That depends a lot on whats attached to the shaft,
                how fast it&#39;s turning, and what&#39;s driving it.=A0 Ob=
vious
                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&#39;t already have anythin=
g
                else that might work, interrupter and divide by is
                probably the most direct method. Sensing the driving
                forces can be a lot of things,=A0 from stepper motor
                pulses to spark plug firing. <br>
                <br>
              </div>
              <div>What&#39;s the application?<br>
              </div>
              <div><br>
              </div>
              <br>
            </div>
            <div>
              <div>
                <div class=3D"gmail_extra"><br>
                  <br>
                  <div class=3D"gmail_quote">On Wed, Jan 22, 2014 at 3:00
                    PM, Rob Butts <span dir=3D"ltr">&lt;<a href=3D"mailto:r=
.butts2 AT gmail DOT com" target=3D"_blank">r DOT butts2 AT gmail DOT com</a>&gt;</span>
                    wrote:<br>
                    <blockquote class=3D"gmail_quote" style=3D"margin:0px 0=
px 0px 0.8ex;padding-left:1ex;border-left-color:rgb(204,204,204);border-lef=
t-width:1px;border-left-style:solid">
                      <div dir=3D"ltr">
                        <div>I have a shaft that I want to measure the
                          rpm of.=A0 I&#39;m looking for opinions on the be=
st
                          and cheapest way.=A0 The design is still in
                          development phase so I have freedom.</div>
                        <div>=A0</div>
                        <div>Thanks</div>
                      </div>
                    </blockquote>
                  </div>
                  <br>
                </div>
              </div>
            </div>
          </blockquote>
        </div>
        <br>
      </div>
    </blockquote>
    <br>
  </div></div></div>

</blockquote></div><br></div>

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