12 Hour analogue clock from speedometer- Feasible?

Ok so what I have is an old speedometer as pictured

What I have in front of me is my Arduino UNO, an Adafruit Motor Shield V2 and 28BYJ-48 Stepper motor.

What I want to do is slowly increment the hand on the speedometer from 0mph (12 o clock) through the hours up until 120mph (11:59) and then the arm swing back to the beginning.

What I want to know is, is the stepper motor the best idea? Would a servo be better? Anyone got any other ideas?

Thanks!
Ash

Does the speedo still have all its inards?

Mark

That speedo might be worth a few bob ...

Yes a stepper is the way to
Go and should do the job fine. You’ll need to junk most of the speedo innards and drive the hand direct.

You could also have a minute hand...

Thanks, the speedo does have its innards but its chromatic so it used a cable that spins a magnet to move the needle so I can't use its built in function!

How can I program the motor to move at the correct rate togo from 0 to 12? I am a little new to this!

Thanks
Ash

If it’s chronometric sell it and buy something else - chronometric speedos are worth a fortune !! (£00’s) and you’ll just wear it out or break it . Please don’t do that !!

If you bought a more modern dash instrument , you may well find it’s already driven by a stepper motor.

Anyhow I don’t think it would work as you suggest as a stepper would not be quick enough

hammy:
If it’s chronometric sell it and buy something else - chronometric speedos are worth a fortune !! (£00’s) and you’ll just wear it out or break it . Please don’t do that !!

If you bought a more modern dash instrument , you may well find it’s already driven by a stepper motor.

Anyhow I don’t think it would work as you suggest as a stepper would not be quick enough

No its not an antique I think its a reproduction of the smiths speedometer! I want it to move very slowly over a 12 hour period and then move back to 0 once 12 is hit (doesn’t matter if it takes a while to get back as long as it stays in sync with time!

Cheers
Ash

But you have to rotate the input continually for the needle to move , maybe 100rpm or so at 12 O’clock which a stepper won’t easily do. It’s also likely the needle will waver about a fair bit as well as making a lot of noise .

That speedo would be about £600 to buy ...

Hi yeah sorry my plan was to gut the speedo and just use my stepper to move the needle directly.

Even with a proper motor in there I dont want it spinning constantly to keep the needle at a certain time is all!

Yeah this isn't an original it cost me £15!

Cheers
Ash

A normal DC motor would work with the original innards. You can control the speed of the motor (and hence the indication of the time) using PWM. Over a period of 12 hours, you will need to increase the PWM from O to the value that corresponds to 120 mph.

Removing the innards will give you other options; I'm not familiar with steppers and servos so can't really advise there.

If I were to run this on a motor, what attachment/pinion would I need for the end to fit a speedometer square cable end? I have searched every term I can think of and just get back normal pinions!

Thanks!