Speed Sensor Wiring
ditchlewis - 25/9/07 at 09:06 PM
Just got my new speed sensor, and it is nothing like the old one
the last one had two wires, one to the guage and one to earth. nice and simple for me
the new one has three cables.
the first is to a fused ingition controlled power supply.
the second it to the guage.
the third is to a 12v negative earth.
the is also a LED on the top near the cables.
the first thing to do is to check i have the right one.
next how do i wire it?
the power suppy is easy. i just find a green spare cable under my dash, there are a few
the next is wire the cable to the sensor.
the last part ??????
What is a 12v negative earth? is this the battery negative terminal? or the chassis?
HELP my SVA is only a week away and time is running out.
Ditch
Rescued attachment sensor.JPG
dave1888 - 25/9/07 at 09:09 PM
12v negative earth, is ground or -
NeilP - 25/9/07 at 09:12 PM
Ditch,
12v Neg Earth is earth - As near as poss. to the sensor.
Live feed from ignition and feed back to speedo. LED comes on when then head senses metal in proximity. If you have a solid mounting try and get the
head to 0.5mm to the metal elements you are sensing. If these are the sides of the bolt heads on the prop then try and tighten these such that they
are all parallel to the head. At high speed, if the head is to far away then you will get a weak signal and the speedo will 'top out' at a
certain speed. LED isn't a good indication of signal strength at speed (but looks pretty at night)..
Neil.
ditchlewis - 26/9/07 at 07:01 AM
I had magnets with the last sensor is it a good idea to use these, or is it better to use the bolts that hold the propshaft to the diff as
these are less likley to come adrift ????
ditch
tks - 26/9/07 at 08:16 AM
prop bolts is your best thing, the sensing distance can vary between 1mm and 10mm (mine only needs 7mm), if you need to be close, build the mounting
as stable as you can. also i advice you to hurry up because that kind of sensors are there in 2 types PNP and NPN...
Tks
ditchlewis - 26/9/07 at 09:26 AM
PNP ?
NPN ?
what are the differences? and how will this affect me
ditch
David Jenkins - 26/9/07 at 09:34 AM
Ditch,
It sounds like you've got a different kind of sensor! The old one was the type that triggered when a magnet went past - usually there's a
reed relay inside (or electronic equivalent) and the device works like a switch - just on-off.
The new one sounds like a hall-effect sensor, which is a fancy way of saying that it detects any ferrous metal going past - no magnets required. This
type has to be mounted where something steel is going past, i.e. the bolt heads where the propshaft meets the diff flange.
It needs 3 leads, because 2 are for the power supply - 12v (switched) & chassis - and the other for the signal back to the speedo. You may well
have to re-arrange the wiring on the speedo to make it work.
HTH,
David
tks - 26/9/07 at 09:37 AM
quote:
Originally posted by ditchlewis
PNP ?
NPN ?
what are the differences? and how will this affect me
ditch
Well basicly it means the state of the line when nothing is captured (no bolt).
The line could then be High (12 volts) or low 0 volts. I guess the speedo needs a pulse when a bolt is sensed. sow when nothing is captured you need
the signal line to be low.
(most of the time = led off)
Hope it makes sense.
Tks
NPN and PNP revers to the type of transistor wich permits you to generate a signal.
One can sunk power and the other can source power. Never short your signal line, because it will mean you kill your sensor. (you then
sunk/source to much power from it)
to test it it is easy, hook it up to your battery and look at the led/signal line if it captures a bolt it should go high (led active)
that way you can easyly test the sensing distance. (always go a little bit closer then needed)
tks - 26/9/07 at 09:41 AM
in case you have the wrong one, i reckon its easy to make a converter for less then 1 pound. in that way you could get it to work for sva.
Tks
ditchlewis - 26/9/07 at 09:55 AM
I've just talked to europaspares and the sensor is a direct replacement for the one i had before except it does not require magnets.
was told to place it over the bolts or preferably the UJ and wire the sensor to the guage as before and provide power supply.
even a complete electrical Numpty like me should be able to do that
well ever onward and upward. 
will i get this finished in time i feel another "when are you going to sell that car" comming on from SWMBO 
ditch
tks - 26/9/07 at 09:58 AM
quote:
Originally posted by ditchlewis
I've just talked to europaspares and the sensor is a direct replacement for the one i had before except it does not require magnets.
was told to place it over the bolts or preferably the UJ and wire the sensor to the guage as before and provide power supply.
even a complete electrical Numpty like me should be able to do that
well ever onward and upward.
will i get this finished in time i feel another "when are you going to sell that car" comming on from SWMBO
ditch
Well go to the garage then en stard wireing.....
Tks
