[Diy_efi] Stepper Motor to drive mechaical speedo

[jayjunk at laserpubs]

On 10/19/2012 11:44 PM, jimster1 wrote:
> Normally it's going to be 1000 turns\mile.  Dials out to be 60MPH as well.
> Some British speedos are different, but are usually marked in tiny script on
> the face.
> Jim

Thanks-
I looked around a bit more last night.

AutoMeter says 1000 RPM at 60 MPH.

That means the drive motor - stepper or DC - needs to run 2000 RPM for 
120 MPH,etc.
Seems like a 500 RPM stepper will probably not do the job.

comment- Driving a DC motor - instead of doing PWM on a fixed frequency, 
do it the other way-
Deliver a fixed pulse width on variable freq- like (for example) the 
pulse train that you get fromm the speed sensor.
To calibrate the motor speed, adjust the pulse width.

FWIW
Jay


> -----Original Message-----
> From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org] On
> Behalf Of jayjunk at laserpubs
> Sent: Friday, October 19, 2012 9:23 PM
> To: diy_efi at diy-efi.org
> Subject: Re: [Diy_efi] Stepper Motor to drive mechaical speedo
>
> Ok - is there a standard revs/mile for a speedometer/odometer?
> The only thing I found so far is for a Vincent motorcycle!
> (1600 rev/mile)
>
> cheers...
>
> On 10/19/2012 5:04 PM, jayjunk at laserpubs wrote:
>> Funny- I was going through my garage and found my stash of gauges.
>> I found a 120 mph mechanical speedo (SW style) that will be just fine
>> for my mutant Corvair.
>> Now I need to look around for a DC motor with enough grunt to drive the
>> speedo!
>>
>> cheers
>> Jay
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