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stepper motor driven speedo

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mattaston

New Member
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
 

Sceadwian

Banned
Sounds like you need a micro controller =) It can (with a proper drive) run the stepper and read the frequency from your hall sensor.
 

picbits

Well-Known Member
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.
 

mattaston

New Member
yes i am in the uk, finding an astra gte could be fun, whats a vectra b?
is the second model vectra or something?
 

picbits

Well-Known Member
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 ?
 

mattaston

New Member
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
 

picbits

Well-Known Member
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.
 

Mickster

Well-Known Member
Most Helpful Member
A magnet/sensor arrangement on the driveshaft/propshaft is going to be a bit messy....
With something welded to the prop or driveshaft, you're also likely to end up with vibration issues too.
 

mattaston

New Member
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.
 

picbits

Well-Known Member
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.
 

picbits

Well-Known Member
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.
 

Mickster

Well-Known Member
Most Helpful Member
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.
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...
 

picbits

Well-Known Member
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.
 

Mickster

Well-Known Member
Most Helpful Member
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...
 

picbits

Well-Known Member
Or car audio installer. They have various devices to sort out the old satnav systems which need a VSS.
 

gerritv

New Member
Your type 9 gearbox has either an electronic or cable driven sender on the rear housing according to Page 4. 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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