Detect Signal

[ronsimpson]

My car gives one count per turn of the drive shaft. (output of the transition)
Multiply by the turn ratio of the rear end multiply by the tire circumference.
You just need to count how many pulses per km or mile. Build a counter with a PIC and drive for 1 mile. Every kind of car is different. You need to do the experiment.
Simple project.

[skimask]

My car gives one count per turn of the drive shaft. (output of the transition)
Multiply by the turn ratio of the rear end multiply by the tire circumference.
You just need to count how many pulses per km or mile. Build a counter with a PIC and drive for 1 mile. Every kind of car is different. You need to do the experiment.
Simple project.

Relatively simple project. I have to wonder how 'ugly' that signal will be coming off the sensor, travelling up the wire to the PIC, etc. Might have to square it off a bit with a 7404 or something along those lines so the PIC doesn't get false triggers.

[sougata]

Hi,

Most probably you would be getting a variable frequency signal. If you have access to a frequency meter (most multimeters have) then measure the frequency while driving at a fixed speed. You get an idea of the number of pulses/per second available a certain speed. Do it for other speeds as well to find if the relationship is correct. Only take care while driving and taking the reading.

[angrysmileyface]

Unfortunately I do not have a frequency meter. best I have is a cheapo Radio Snack multimeter with AC/DC, Diode test and Amperage. So I am rather stuck trying to ascertain what the signal looks like by what I have on hand. Now if I had the gear I had back in college, it would be a diff story.

Basically I think I will count the pulses that show up, unless someone has a better idea (This is a 93 honda civic btw)

[mackrackit]

Unfortunately I do not have a frequency meter.

You are building one. Be sure to look at the COUNT command in the manual. I use something similar to monitor fan and blower speeds.

A hall effect sensor is often used. If the wiring is good the signal will be "OK". The first few blade speed monitors I built used sensors from autos.

[Pic_User]

1992-1995 Honda Civic Cruise Information

Constant 12V+ White Ignition Switch Harness or Use Hot Side of Brake
Switched 12V+ Black/Yellow Ignition Switch Harness
Ground Use Chassis Near Cruise Control Module
Hot Side of Brake n/a Brake Switch
Cold Side of Brake Green/White Brake Switch
Tach Blue Distributor
VSS Lead Yellow/Blue Driver's Side Dash, above Fuse Panel, Gray Connector
Pulses Per Mile 4000 PPM

http://www.hondafactor.com/v2/showpo...55&postcount=5

“Your mileage may vary”
-Adam-

[skimask]

VSS Lead Yellow/Blue Driver's Side Dash, above Fuse Panel, Gray Connector
Pulses Per Mile 4000 PPM

http://www.hondafactor.com/v2/showpo...55&postcount=5

There ya go. Use the VSS signal to trigger an interrupt, keep track of the pulses in a word variable...Bam...done...except for the building, and the programming, putting it in a box, testing it on the car, etc.etc.