[Diy_efi] Stepper Motor to drive mechaical speedo

[Steven Donegan]

I'll beg to differ as I just took 2nd place in a race with a digital speedo (.18 seconds off the first place guy) :-) But if you believe in that theory then more power to you :-)

The goal of the race is to be exactly on time... My target was 100 mph, my actual was 99.something :-)

____________
Steven Donegan
SSCC/NORC Life Member, Car #86
www.sscc.us

--- On Sun, 10/14/12, ScottyGrover at aol.com <ScottyGrover at aol.com> wrote:

From: ScottyGrover at aol.com <ScottyGrover at aol.com>
Subject: Re: [Diy_efi] Stepper Motor to drive mechaical speedo
To: diy_efi at diy-efi.org
Date: Sunday, October 14, 2012, 3:59 PM



 
 

An analog (needle) speedo is easier to read and provides more (intuitive) 
information than a digital unit.
?
Scotty from Hollyweird
?
.
?

In a message dated 10/14/2012 8:25:35 A.M. Pacific Daylight Time, 
donegan at donegan.org writes:

  
    
    
      Why? A simple digital speedo would be much simpler and 
        likely more accurate? Just curious.


        ____________
Steven Donegan
SSCC/NORC Life Member, Car 
        #86
www.sscc.us

--- On Sun, 10/14/12, Hugh Keir 
        <hugh at sol.co.uk> wrote:

        
From: 
          Hugh Keir <hugh at sol.co.uk>
Subject: [Diy_efi] Stepper Motor 
          to drive mechaical speedo
To: "diy_efi at diy-efi.org" 
          <diy_efi at diy-efi.org>
Date: Sunday, October 14, 2012, 3:14 
          PM


          Hi Guy's

I have been trying to sort out a 
          stepper motor to drive a mechanical
speedo on a TR7.

The 
          problem started after an engine and gearbox change from a car with 
          no
mechanical speedo drive and also a change of diff 
          ratio.

As a first step, I bought a 28BYJ-48 12V stepper motor 
          from ebay plus a
controller with on board frequency generator to 
          drive.

The first problem I have faced is that the stepper motor 
          is not capable of
spinning fast enough to drive the 
          speedo.

It seems to peg out at about 160Hz measured at one of 
          the stepper motor
phases, any faster on the input and the stepper 
          motor freezes.

The declared stepper motor frequency is 100pps 
          with a step angle of 5.625?
and a step reduction of 1/64 on the 
          gearbox which I calculate should be
2.5 RPM. I reality I am getting 
          18RPM, either way this is not fast enough.

I intend using a 
          GT101 hall sensor on the propshaft to feed a digital
pulse to an as 
          yet to be sorted stepper motor control board.

I wonder if 
          anyone has attempted anything 
          similar?

Thanks

Hugh




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