[Diy_efi] Stepper Motor to drive mechaical speedo

[Hugh Keir]

Guy's,

Thanks for taking an interest.

Got my stepper motor working tonight, but it is still not fast enough.

Looks like 120 input RPM from the stepper motor was showing 10 MPH.

The speedo tops out at 150 MPH, so something around 1800 RPM maximum input
RPM will give the performance required at the speedo.

I have used the GT101  hall sensor many times before and is a good option
to provide a reliable input frequency.

http://docs-europe.electrocomponents.com/webdocs/002e/0900766b8002e127.pdf

Need to see what sort of Servo motors would provide the performance required.

The stepper motor I tried tonight, SY35ST28- 0504A, has a holding torque
of 1000 gram /cm and a detent torque of 80 gram / cm.

http://www.robotshop.com/content/PDF/specifications-sy35st28-0504a.pdf

Thanks

Hugh


I'm not really a PIC man, more 8051, motorola,
the freq source is the issue, it might already have signal conditioning
or not, if the distance is not far then u wont need much protection on
the input to the pic, some is always good though, screened leads
help too as EHY gets around flakey corroded grounds in cars, some
'load dump' protection is good too, eg reverse polarity, 2xbatt re faulty
jump starts, that sort of thing etc... so whats the freq source ?
regards
mike


I've built several PIC projects before. What sort of frequency are you
dealing with?


At 10:15 PM 22/10/2012, you wrote:
>My new stepper motor arrived at work today, so if it is fast enough to
>drive the speedo, I will post a youtube video showing what the set-up
>looks like.
>
>Whatever happens regarding the stepper motor / servo motor solution, I
>will need some sort of programmable output to drive the speedo.
>
>Turns out that I also need a speed input to the ECU and also to the Corsa
>( UK ) electronic power steering system I am going to graft on to the car.
>
>It would be great if someone can show how to manipulate the pulses from
>the hall sensor with a PIC.
>
>Thanks
>
>Hugh
>
>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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