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From: Dave Kerber <dkerber AT warrenrogersassociates DOT com>
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Date: Thu, 23 Jan 2014 09:33:28 -0500
Message-ID: <0b0750d2097334a10a9c03e2f9b09599@mail.gmail.com>
Subject: RE: [geda-user] Best way to measure RPMs
To: geda-user AT delorie DOT com
Content-Type: text/plain; charset=ISO-8859-1
Reply-To: geda-user AT delorie DOT com

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
>
>
>
>
>
>