[Diy_efi] Stepper Motor to drive mechaical speedo

[ScottyGrover at aol.com]

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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