[Diy_efi] Stepper Motor to drive mechanical speedo

Harold Bruulsema habruulsema
Sat Oct 20 14:44:34 UTC 2012


I had a completely different idea of what you were looking for, since your first post.
My concept of using a stepper to drive a speedometer was always to use a stepper connected directly to the pointer. Rip out all the guts of the speedo, bolt in a stepper motor, attach the pointer to the stepper shaft. You would lose the odometer function, but would get an accurate speedo.
If you used a 200 ppr stepper, and run it half-step, you would get 400 increments per revolution. If the speedo scale covers 0-150 mph over 270 degrees, you would get resolution of 1/2 mph per step.
You would need to have a peg at 0, and each time at startup you would run a homing routine, where you run the stepper say 400 steps in reverse (against the peg), to make sure it is in sync with where the ECU thinks it is (in case you lost power with the needle not at 0).

Harold


________________________________
 From: "diy_efi-request at diy-efi.org" <diy_efi-request at diy-efi.org>
To: diy_efi at diy-efi.org 
Sent: Saturday, October 20, 2012 7:27:12 AM
Subject: Diy_efi Digest, Vol 12, Issue 26
 

Hi Mike,

I am not an electronics engineer, so have perhaps headed off on a tangent.

If you were able to post links to the pieces of kit that you would use,
that would be a great help.

I have a PICkit 3 programmer and am familiar with the principle of PWM,
but not how you would put it all together.

One of the biggest problems is tweaking the frequency output of the hall
sensor to drive the speedo at the right speed.

Perhaps some eBay links of the items you propose would help with the
global sourcing of parts.

Cheers

Hugh

Hi Hugh,


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