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Mail Archives: geda-user/2014/01/22/15:30:21

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Date: Wed, 22 Jan 2014 20:30:09 +0000
From: Ed Simmons <ed AT estechnical DOT co DOT uk>
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To: geda-user AT delorie DOT com
Subject: Re: [geda-user] Best way to measure RPMs
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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
> <mailto: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
>     <mailto: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 class="moz-cite-prefix">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.<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<br>
      <br>
      On 22/01/14 20:23, Rob Butts wrote:<br>
    </div>
    <blockquote
cite="mid:CALSZ9gpRgtDUnnvHVGY8zLdWNrAiaEUb5gM3va8vTSbfc+Dr6A AT mail DOT gmail DOT com"
      type="cite">
      <div dir="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.&nbsp; I don't have any encoder
        yet and I can attach anything to the shaft.</div>
      <div class="gmail_extra"><br>
        <br>
        <div class="gmail_quote">On Wed, Jan 22, 2014 at 3:13 PM, Nathan
          Stewart <span dir="ltr">&lt;<a moz-do-not-send="true"
              href="mailto:therealnathanstewart AT gmail DOT com"
              target="_blank">therealnathanstewart AT gmail DOT com</a>&gt;</span>
          wrote:<br>
          <blockquote class="gmail_quote" style="margin:0 0 0
            .8ex;border-left:1px #ccc solid;padding-left:1ex">
            <div dir="ltr">
              <div>That depends a lot on whats attached to the shaft,
                how fast it's turning, and what's driving it.&nbsp; 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,&nbsp; from stepper motor
                pulses to spark plug firing. <br>
                <br>
              </div>
              <div>What's the application?<br>
              </div>
              <div><br>
              </div>
              <br>
            </div>
            <div class="HOEnZb">
              <div class="h5">
                <div class="gmail_extra"><br>
                  <br>
                  <div class="gmail_quote">On Wed, Jan 22, 2014 at 3:00
                    PM, Rob Butts <span dir="ltr">&lt;<a
                        moz-do-not-send="true"
                        href="mailto:r DOT butts2 AT gmail DOT com" target="_blank">r DOT butts2 AT gmail DOT com</a>&gt;</span>
                    wrote:<br>
                    <blockquote class="gmail_quote" style="margin:0px
                      0px 0px
0.8ex;padding-left:1ex;border-left-color:rgb(204,204,204);border-left-width:1px;border-left-style:solid">
                      <div dir="ltr">
                        <div>I have a shaft that I want to measure the
                          rpm of.&nbsp; I'm looking for opinions on the best
                          and cheapest way.&nbsp; The design is still in
                          development phase so I have freedom.</div>
                        <div>&nbsp;</div>
                        <div>Thanks</div>
                      </div>
                    </blockquote>
                  </div>
                  <br>
                </div>
              </div>
            </div>
          </blockquote>
        </div>
        <br>
      </div>
    </blockquote>
    <br>
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