X-Authentication-Warning: delorie.com: mail set sender to geda-user-bounces using -f X-Recipient: geda-user AT delorie DOT com Message-ID: <52E02A51.5090008@estechnical.co.uk> Date: Wed, 22 Jan 2014 20:30:09 +0000 From: Ed Simmons User-Agent: Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: geda-user AT delorie DOT com Subject: Re: [geda-user] Best way to measure RPMs References:

In-Reply-To: Content-Type: multipart/alternative; boundary="------------040306070704050901090901" X-Authenticated-As: ed AT estechnical DOT co DOT uk Reply-To: geda-user AT delorie DOT com This is a multi-part message in MIME format. --------------040306070704050901090901 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit 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 > > 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 > 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 > > > --------------040306070704050901090901 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit

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

--------------040306070704050901090901--