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Speed sensors and speedo's
garybee - 6/7/11 at 11:50 AM

Hoping someone can help me with this one...I have a speedo designed to use an inductive sensor.

Is it possible to use a magnetic (reed switch) pickup with this speedo, or must I use an inductive sensor?

Can I use magnets to increase the range of an inductive sensor?

Is it possible to tap into the Vehicle Speed Sensor (taken from a FWD Ford, fitted into the output of the Type 9 'box) to provide an acceptible signal for this speedo'? The VSS is currently there only for the ECU to use.

I would appreciate any insight into this that people may have.

[Edited on 6/7/11 by garybee]

big_wasa - 6/7/11 at 02:27 PM

The mondeo feeds both the clocks and ecu from the same hall affect sensor. Works with the sensor in my mt75.

garybee - 6/7/11 at 05:13 PM

quote:
Originally posted by big_wasa
The mondeo feeds both the clocks and ecu from the same hall affect sensor. Works with the sensor in my mt75.


Have you used the sensor in your MT75 to supply a signal to a speedo? If so, which two of the cables have you used (I'm assuming you're using a three wire sensor)?

Edit: Had a look at the wiring diagrams. It looks like the three cables going to it are posative feed, negative and a signal wire. If this signal wire outputs a signal appropriate for an aftermarket speedo then this would be a very easy way, no mucking about with extra sensors and magnets etc.

[Edited on 6/7/11 by garybee]

garybee - 7/7/11 at 02:12 PM

After a bit more research...

The Ford 3-wire VSS outputs a 10V 'square wave' signal, so wouldn't do any good to a speedo' designed to use an inductive sensor.

Does anyone know of a way to change the 10V DC 'square wave' signal to one that my speedo' can use?

MikeRJ - 7/7/11 at 03:46 PM

A simple differentiator (AKA high pass filter) will AC couple the signal and give something that approximates an inductive sensor output. You might just get away with AC coupling the VSS output, i.e. connect a suitable value capacitor in series with the signal wire that goes to the speedo head.

i_froloshki - 1/6/12 at 01:51 PM

Hello all,
i am at a stage to connect the speedo. The problem is that on my Mt75 i have electrical vss, but mechanical speedometer. Is it possible to get a mechanical speed sensor and replace the electronic one so i can use my cable meter?
Thanks in advance.

Yavor

snowy2 - 2/6/12 at 07:31 AM

My speed sensor uses a magnet on the wheel hub and a sub miniature reed switch. that has been replaced once or twice but i have found the two pole reed switches to be the most reliable, the present one has lasted a couple of years and 15000 miles with no trouble. I use the N/O connection and present the reed switch "end" on to the magnet, it is more sensitive that way (counter-intuitively)

snowy2 - 2/6/12 at 07:36 AM

quote:
Originally posted by garybee
Hoping someone can help me with this one...I have a speedo designed to use an inductive sensor.

Is it possible to use a magnetic (reed switch) pickup with this speedo, or must I use an inductive sensor?

Can I use magnets to increase the range of an inductive sensor?

Is it possible to tap into the Vehicle Speed Sensor (taken from a FWD Ford, fitted into the output of the Type 9 'box) to provide an acceptible signal for this speedo'? The VSS is currently there only for the ECU to use.

I would appreciate any insight into this that people may have.

[Edited on 6/7/11 by garybee]


i do not think it would work as the sensors work in a different way.....the inductive sensor usually generates a variable voltage depending on speed the reed switch just puts pulses on a wire (on + off) which have to be counted.

i_froloshki - 7/6/12 at 05:49 AM

Hi all,
it seems that i just need a mechanical MT75 speedo so i can mount it to the box. Anyone know part number or where can i get one?

Thanks

Yavor

johnemms - 17/2/13 at 04:53 PM

Sorry to butt in but does any one know what wires
are what on a ford 3 wire speed sensor?
I got:
Black with small brown stripe
Brown no stripe
Yellow with small brown stripe
cheers

mactoss - 18/10/13 at 09:00 AM

Did u find out what the wires were?