Mail Archives: geda-user/2014/01/22/15:51:34
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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'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" 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"><<a href=3D"mailt=
o:ed AT estechnical DOT co DOT uk" target=3D"_blank">ed AT estechnical DOT co DOT uk</a>></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'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<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'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"><<a href=3D"mailto:therealnathanstew=
art AT gmail DOT com" target=3D"_blank">therealnathanstewart AT gmail DOT com</a>></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's turning, and what'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'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'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"><<a href=3D"mailto:r=
.butts2 AT gmail DOT com" target=3D"_blank">r DOT butts2 AT gmail DOT com</a>></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'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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