type of pulse from speedo hall effect sender...???

[leso]

ok..i am putting a speco electronic speedo in my celica, it needs me to program how many pulses per km...so i thought it would be easier to use a gps to measure a km and a pulse counter to measure pulses from my speedo sender.. went to jaycar and found a 4 digit counter (DC-500) used with a door entry alarm ...the guy there said that it needs a negative pulse input, the info sheet says that the door alarm output is npn.

This brings me to my question..what type of output does a speedo sender have..????

And if anyone finds this thread in a search in the future, if this counter works ...pm me and you can borrow it..

cheers leso

[td42gq]

all toyota sensors that I have come across are just a square wave signal 12v up and 0v down and the duty cycles gets faster the faster they turn - Hall effect sensor if you want the technical term

Aaron

[td42gq]

Some small mathematical calculations would be alot easier,
count the number of teeth on the speedo drive and multiply it by your diff ratio and the multiply that by your rolling diameter which give you pulses per tyre revolution.
Then to work out per/km divide your rolling diameter in metres by 1000 and times that answer by your pulses per tyre revolution and you have your
pulses per km.
If you need a fairly accurate tyre rolling diameter try here:
http://www.miata.net/garage/tirecalc.html

[td42gq]

I just realised that i got that slightly wrong, the amount of teeth on the speedo gear doesn't matter, a toyota speed sensor outputs a 4 pulse signal for every revolution of the rotor shaft. The only problem with this is you need to work out how many times the speedo drive turns per tailshaft rotation in order to do the calculation so this may be of no real help to you after all.

I must be tied cause after all that it is probably of no help to you at all. Sorry for wasting your time..

[td42gq]

ok after feeling like a nob I have gone and had a drink and come back with the solution to your problem.
remove the speedo drive and on the end of the speedo drive there is a number should be 31/10 or 29/9. This is your drive ratio. Then using that devide the numbers to get your ration against tailshaft rotation. So you should get something like 3.1 if its a 31/10. devide 3.1 by 4 to get your pulses per revolution should .775 in this case.
then you can times that by the diff ratio and so on as above and you will get your pulses per km that way. Should be a bit easier to work out to an accurate number and should make your speedo a lot more accurate.

May have taken 3 posts but I got there in the end.

[wilbo666]

I can't remember for 100%, but I have a feeling Toyota is push/pull (i.e. outputs +12V and GND).

If you want to only have it connect to GND you could install a diode (i.e. 1N4004, etc) facing like so...

[speed sensor output] ---|<|---- [pulse counter]



Cheers
Wilbo