Detect Signal

[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.

[mister_e]

Both Vss and Tach can be find easy under the dash for this car as well. Usually on the top of the fuse box. There's a lot of connector, just use the same wire color.

[angrysmileyface]

Ok got a little code here. Not quite sure if its what I want for this purpose, so excuse me if there are some errors. Basically I want it to count the pulses coming off the VSS and Im trying to use the VSS as a the interupt to start the process when it starts registering milage. I do not know if I configured the interupt process correctly as well as its not shown here, but I would like to be able to save the milage to some portion of the eeprom memory when the car is shut off. I intend to use a 16F877A for this project. Insight or help is greatly appreciated. Thanks.

Define LOADER_USED 1 'required if bootloader used to
'program PIC
DEFINE LCD_DREG PORTC 'Define PIC port used for LCD Data
'lines
DEFINE LCD_DBIT 4 'Define first pin of portb
'connected to LCD DB4
DEFINE LCD_RSREG PORTC 'Define PIC port used for RS line of
'LCD
DEFINE LCD_RSBIT 3 'Define PortC pin used for RS
' connection
DEFINE LCD_EREG PORTC 'Define PIC port used for E line of LCD
DEFINE LCD_EBIT 0 'Define PortC pin used for E
'connection
DEFINE LCD_BITS 4 'Define the 4 bit communication
'mode to LCD
DEFINE LCD_LINES 2 'Define using a 2 line LCD
DEFINE LCD_COMMANDUS 2000 'Define delay between sending LCD
' commands
DEFINE LCD_DATAUS 50 'Define delay time between data sent.
OPTION_REG = %00111111 'Not sure if this is needed.
plscntr var WORD
milage var word


plscntr = 0 'Reset pulse counter
ON INTERRUPT goto miles_start
INTCON = $90
Start:

lcdout $fe, 1 ' Clear LCD
lcdout $fe, 2 ' Position cursor at home
LCDOUT #milage ' Initially display Milage
Pause 1000 ' Pause for 1 second to see it
If PortA.1 = 1 Then milage = 0 'Reset the milage indicator if reset button pressed
Goto Start ' Loop back and do it all again


miles_start:
if PortA.5 = 1 then plscntr= plscntr +1 'add the pulses

if plscntr = 4000 then
plscntr = 0
milage = milage+1
lcdout $fe, 1 ' Clear LCD
lcdout $fe, 2 ' Position cursor at home
LCDOUT #milage ' Display Milage
EndIF
goto miles_start
end