speedo wiring using the hall effect generator
indyian - 25/8/08 at 08:20 PM
can any one help me iv got smiths speedo and im using the hall generator but i have no instructions on how to wire it to the head or what the
converion i need to do to set the switches on the back iv been on green guages and found the tables for the switches but need to know how many poles
the sensor has then what to do with that number once iv got it can anyone help? please
02GF74 - 26/8/08 at 06:37 AM
so you want to know two tings.
1. how to wire sensor to speedo?
2. how to program speedo?
can't help you with first since although I know the principle, I am not familiar with t he smiths speedo wires.
there have been loads of post about setting the speedo but basically what they generally require is the number of pulses per mile.
you need to follow the steps.
1. compute or measure circumfernece of tyre
2. divide that into 1 mile so you have number of wheel turns per mile
now depending on where you mount the sensor:
a) on the wheel - nothing to compute
b) on prop - multiply number above by diff ratio
c) on gearbox - multiply number above by speedo drive ratio
3. multiply number above by number of magnets.
this is the number you program the speedo with.
big_wasa - 26/8/08 at 07:32 AM
Question 2)What he is asking is how many poles the hall effect sensor has, This is what he needs to put into the equation.
Ie sealed black box and know magnets to see.
Just stick any number into the gauge dip switch and see what speed it gives. Go up or down untill you get what you want.
02GF74 - 26/8/08 at 07:42 AM
quote:
Originally posted by big_wasa
Question 2)What he is asking is how many poles the hall effect sensor has, This is what he needs to put into the equation.
hall effect sensor has no poles - internally there is a slab of special silicon material in which there are free electorns that are affected by an
external magnetic field.
There is electonics that detects them to produce a signal that can be binary or in proportion to the strength of the field.
wikipedia I am sure can give you the true story in case I have misremembered it.
NOTE: looking up hall effect sensor in wikipedia, although it shows a nice picture, it is in fact describing an inductive sensor.
As I mentioned in the computation, you need to take into accunt the number of magnets.
[Edited on 26/8/08 by 02GF74]
big_wasa - 26/8/08 at 08:41 AM
Ok,some of the web info refers to them as poles 
So for the seedo sums, how many magnets ?
I cant tell if its 6 or 8.
For every 3.5 revs of the prop in 4th gear (1:1) on a t9 the senor out put rotates once.
Conecting the sensor to the speedo is easy.
Green from gauge is +12v (pin 1)
Black from speedo sensor +12v.
So connect both to a switched fused +12v supply.
Black from gauge(pin 5) is earth.
Brown of sensor also to earth.
White/Black from gauge (pin 6) wants to go to your yellow wire on the sensor.
And thats it 
ive just been out and hooked my dash upto the sensor and spun it with the drill
big_wasa - 26/8/08 at 09:08 AM
Ok so reading on, There is one magnet and x amount of windows in the disc that pass it.
02GF74 - 27/8/08 at 11:33 AM
ok, so we know a bit more about the sensor.
A slotted steel disc between a single magnet and hall sensor will work; as ^^^ says, hall effect sensor measures strength of magneitc field which
will be interrupted by the slotted disc.
so replace the number of magnets by number of slots in step 3. of my original post.