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electronic speedo
02GF74 - 1/3/07 at 09:01 AM

qucik question; I believe these work by having a stepper motor move a pointer so if you turn of the ignition and the car is not stationary, I assume the pointer will not be a 0 mph?

So when you power up, does the pointer move to repositioning itself to 0 mph?

tks - 1/3/07 at 09:20 AM

you say a couple of things....

reset is always done by a fixed point in your case it would be a pot meter connected to the shaft ( i guess)
wich will tell you where the 0 is... where the 30 is etc. etc..

ot just only the 0 and x steps per km/h..

in this case its easy for the clock to reset it self and after reset it could start listening to the speed sensor.

in case you have a different speedo it wouldn´t be a problem to because knowing its in the down position (below 0)
it will know the offset to 0 + steps per km/h sow it will remark the correct speed....


there is only one excemtpion and thats when you cut off and directly turnon, then it could be marking 0 and readd the 0 offset.. thats the reason i prefer the potmeter tactics... also if your sensor goes out on higher speed you could recompensate easyer...

Tks

MikeRJ - 1/3/07 at 12:32 PM

quote:
Originally posted by 02GF74
qucik question; I believe these work by having a stepper motor move a pointer so if you turn of the ignition and the car is not stationary, I assume the pointer will not be a 0 mph?


AFAIK only the posh ones (e.g. Stack) use stepper motors, the electronic car speedos I have seen use a simmilar movement to an electronic tacho, i.e. moving coil meter. In fact you could use a tacho as a speedo if you could get the correct pulse rate into it.