02GF74
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| posted on 23/10/07 at 08:59 AM |
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Racetech Speedo sensor
those who have been paying attention, wiill realise I have thrown in the towel for making my own speedometer.
Issues are cost - about £ 50, a lot of time for making electornics and software plus the risk, a big one, that it may not work in the end.
I guess I got fed up and formed out for a Racetech Speedo.
Anyway, that is not the point of this post but signal info. for the sensor is.
(I will be contacting Racetch for the info. but maybe someone here will have used the same speedo.)
From the leaflet:
pin 6 - speed signal input( hall ECU)
pin 7 - speed signal input for low voltage output senders.
So it seems both are inputs, but what is the voltage level for each input? and what is the minimum pulse width?
I am going to make my own sensor. This will be driven by the speedo cable, turning a disc either for a hall or optical sensor. This will fit in the
engine bay.
I have made the mechanical part of a hall effect sender, without electronics and fitted it to the gearbox but there is not a great deal of room and is
awkward to work on plus no routeing of wires under the chassis - hence the speed cable solution.
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BenB
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| posted on 23/10/07 at 11:14 AM |
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If this is the Racetech speedo actually badged AST and sold, amongst others, by Merlin Motorsport then you're in for some fun 
The odometer needs exactly 833Hz @ 100mph. Its totally non-adjustable. The speedo is adjustable but it has no effect on the odometer... So
you're best off getting the signal spot on (ie 833Hz@100mph).
Its designed to use a passive reactance (2 wire) sensor [which they also sell]. This needs to be very close to the trigger wheel (air gap < 2mm).
It'll need to be well fixed because the air gap effects the signal amplitude and my studies have shown that the speedo is amplitude AND
frequency sensitive.... IE wobbly sensor mount = wobbly dial arm 
In the end I got some trigger wheels laser cut that mount on the Lobro joint (diff end) of the driveshaft. Does the job very nicely....
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02GF74
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| posted on 23/10/07 at 12:39 PM |
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It is Racetach made by Racetech, Wallingford, Oxfordshire badged with Racetech, purchased from Europa spares.
it is programmable, calibration range is from 2,500 to 128,000 pulses per mile.
So I would guess the answer to your question is no.
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BenB
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| posted on 23/10/07 at 03:01 PM |
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Fair enough
that's the one I should have gone for.....
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