Speedo Sensor?

[Eamon]

Hey all,

I am curious as to what this chip does that sits atop the automatic Hatch / mighty boy speedo's. And if it is a speed sensor is it possible to make a digital readout for it?

Thanks

[Brayden]

Yes, it is a speed sensor. It connects to the gearbox control unit. I have no idea whether it provides the right type of signal to display speed on an electronic display.
It'd be easier to get the cluster from a Hatch that has a digital speedo.

[Eamon]

Thanks for the input

I have tried with the more common outputs (resistance and voltage) but the result is not linear with the increase in speed. Finding a digital hatch cluster would be really hard id reckon because of the rarity of them let alone the ones with digital.

Do you know the input / output of the control unit as i could maybe get a signal from there?

[rf4burns]

That "Chip" is a reed switch its closed by the magnet mounted on the disc that rotates with the speed o so if you put a resistance meter across it and turn the input to the speed o it will show the resistance changing from zero to infinity -check the auto manual page 21-11 and 21-62 .Its output is directly proportional to the vehicle speed  ;for an auto this is how the thing decides when to change to second (with out kick down and vacuum switch) 

[Zuffen]

Being a reed switch it's most likely putting out a sine wave pattern and not a square wave pattern.

You would need to ensure whatever speedo you plan on using will work with the signal you're getting out of the senor, once you've determined the wave pattern.

[Eamon]

That info helps alot thank you,

Ive looked into how that reed switch works and tested it (silly me thought i would get a straight answer from the multi-meter in km/h). i do not have the auto manual pages that you said i should look at, i am also unsure of what type of digital speedo would take the signal that it puts out. 

Thanks

[Zuffen]

I've installed a few digital speedos and can advise:

VDO needs a square wave and Speco will run on a sine wave.

A square wave is easy to set up using the ignition module from a Falcon as sold by Jaycar.

If you wanted to go that way I could post photos of my setup (it's not on a Mighty Boy) but it wouldn't be hard to organise on a MB.

[Eamon]

Ideally i am after a hatch digital cluster look so if anyone has any photos id appreciate that, so i am thinking of a digital reading from a LCD or such. if not possible i looked into speco gauges and they seen to support both waveforms?

If you could put photos of your setup that would be great to get some ideas.

Thanks

[Zuffen]

Pity its upside down!

These are all VDO guages and I built Hall effect reluctor out of exhaust pipe and a Falcon ignition module to give me 4 pulses per revolution of the tailshaft.

This is in a 2013 Homebuilt vehicle on Full NSW Rego.

[rf4burns]

The manual is available here http://www.teammightyboy.com/workshop/39-tech-info/71-mightyboy-manual  see the bottom of the home page http://www.teammightyboy.com/