stepper motor driven speedo

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mattaston

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hi i am looking into a project to create a speedo that uses a stepper motor, to do away with my analog one i have at present, i could rob something out of cd drive, or hhd. or take out a dash out of a scrap car for the stepper motors. i was planning to use a hall efect device mounted close to the propshaft and weld a trigger wheel to it, that would provide a signal.
i can obviously measure how many rotations of the propshaft equal to 1 mile.

its how to read in the frequency, which in turn then drives the stepper motor accordingly to read the correct speed?

any help or ideas appreciated
 
Sounds like you need a micro controller =) It can (with a proper drive) run the stepper and read the frequency from your hall sensor.
 
Pretty well any will, I would suggest something like the 18 pin 16F628A, or 16F88, as a few spare I/O pins gives you something to play with.
 
What country are you in ?

If you're in the UK then grab a speed sender from an old Astra GTE - they screw onto many types of gearbox and give a nice clean pulse. Also the Vectra B use a stepper motor for their speedometers and you can pick up a whole set of clocs for pennies.
 
yes i am in the uk, finding an astra gte could be fun, whats a vectra b?
is the second model vectra or something?
 
Vectra-A was the Cavalier here over in the UK
Vectra-B was what we know as the Vectra (1996->)

The Astra speed senders are usually about on Ebay for <£20

What car do you drive ?
 
the car it is intended for is a kit car, it is running a lancia 2.0l twincam bolted to a sierra 5 speed box. type 9 job
 
Do your hubs have abs sensors (even if the car doesn't have ABS) ?

Could be worth looking into as you get a nice resolution speed pulse from ABS hubs. Most newer Vauxhalls use the ABS system to give you your VSS signal.

A magnet/sensor arrangement on the driveshaft/propshaft is going to be a bit messy and you won't get a fantastic resolution on lower speeds.
 
unfourtunately it doesnt have abs hubs or brakes, as it uses cortina front hubs, and back axel from a sierra. as to vibration i can get he propshaft re balanced if needed.
 
You're better off getting a sender to screw into the gearbox. Other alternatives are to use a cable driven take off from the gearbox and modify the speedo head. There is normally a small magnet in there that spins round at the same rate as the cable. You could use a hall effect device to pick up this magnet and voila - you have a VSS signal.

If you get hold of a MK3 Astra speedo it goes one step further with an IR reflective disc inside which generates a lovely clean pulse.
 
Hmmm now being a member of six Vauxhall forums and most of my business comes from Vauxhall owners .....

In the last 15 years I've owned:

1988 Astra 1.3 Merit
1990 Astra SXi
1994 Cavalier 1.8GLS
1996 Vectra Sri

Current car is a 1998 Astra 1.6 16v Arctic II Automatic which I'm gradually getting back to its former running glory. Even though its low mileage there was a bit of work needing doing lol.

And to end the Ford/Vauxhall debate, I've had .......

1979 Ford Fiesta 1.1L
1980 Ford Cortina 2.0
1982 Ford Fiesta 1.1L
1983 Ford Escort 1.6 Ghia
1988 Ford Sierra 1.8 L Auto
1990 Ford Escort 1.3L
1990 Ford Fiesta 1.0
1991 Ford Granada 2.0 Ghia X
1994 Ford Mondeo 1.8 LX
1996 Ford Fiesta 1.8 Diesel

The Ford were as reliable if not more reliable than the Vauxhalls but for some strange reason I have been staying with Vauxhall cars recently.

Oh and we've had in the past 4 years:

4 x New VW Passat TDi
1 x New VW Jetta TDi
2 x New Golf TDi GT Sport
2 x New Honda Civic Diesels
1 x New Kia Pro Cee'd Sport TD

Blimey - when its down in writing it makes me look a bit of a car whore lmao.
 
mattaston said:
unfourtunately it doesnt have abs hubs or brakes, as it uses cortina front hubs, and back axel from a sierra. as to vibration i can get he propshaft re balanced if needed.
Click to expand...

In that case, perhaps a photo-interrupter aimed through the propshaft yoke at either end may work? Only tyre circumference & final drive ratio would need to be known, for distance travelled per complete prop revolution, just the same as a hall-effect sensor/magnet arrangement, but nothing is added to the prop and a mounting method may be easier.

Maybe Nigel or Picbits could comment further upon this...
 
Opto sensing in anything other than a semi-sealed environment on a car is a big no-no.

Gearbox sender is by far the easiest and most cost effective way of doing it.
 
Unless a suitable pulse sender can be mated to the Sierra box, maybe a chat with a taxi-meter installer could be another avenue to look into...
 
Or car audio installer. They have various devices to sort out the old satnav systems which need a VSS.
 
Your type 9 gearbox has either an electronic or cable driven sender on the rear housing according to **broken link removed**. Either way it is best to use that than the prop shaft method. If you have the cable type there are plenty of choices to install a pulse generator.

I am building a board for an old (1976) speedometer, the original chips are long ago NLA. Using a PIC12F683, PWM to drive the meter, pulse output to drive the 1-phase unipolar stepper for the odometer.

I am not sure about using a stepper for the speed indication though, how will it return to 0 when you turn off the power? You would need a routine to 0 it on power up....
 
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