so @ 10kM/H you should see 17.3pulses/sec with a inter pulse delay of 57.8ms
@ 40kM/H = 69.4ps = 14.4ms
@ 50kM/H = 86.8ps = 11.5ms
@ 60kM/H = 104.1ps = 9.6ms
@ 70kM/H = 121.5ps = 8.2ms
@ 80kM/H = 138.8ps = 7.2ms
@ 90kM/H = 156.2ps = 6.4ms
@ 100kM/H = 173.6ps = 5.7ms
@ 110kM/H = 190.9ps = 5.2ms
------------------------------------
@ 220kM/H = 381.9ps = 2.6ms

If your uP can time the pulses down to 2.6ms you can have LIVE (ie. instantaneous at each pulse) speed displayed. If your uP isn't that fast, do a .1sec count (divide the pulses/sec number above by 10) and update the speed every 1/10th sec.

Wow,
I didn't make quite that many examples for myself.
Only that the number of pulses p/sec x 60, then divided by 6250,
then x 60 again = Km per hour.

ie. 17.3611 pulses per sec x 60 = 1041.666
1041.666 / 6250 = 0.1666
0.1666 x 60 = 10 Km per hour.

since my mcu don't like decimal, I have to multiply first, then divide,
so it's more like:

pulses per sec x 100, x 60, /6250, x 60, x 100 = Km per hour



Or I could look at the cheats way out..
Does anyone know where the right hand side instrument cluster
leads end up? I would like to find the wire from pin 14 (blue),
if I can do it from under the dash..
Cheers, Art.

pin 14 if I'm not mistaken is the data line from the cluster to the trip computer (if any), so won't be any good to you.

Yeah, that's right, that data line carries the speed on it in serial format
so the calcs are already done. look here:
http://www.fordmods.com/forums/viewtopi ... light=baud

I just pulled my dash apart to tap the speedo out line which is supposed
to be data according to the docs, but it's just another pulsing line
even at 1000 baud it would be easy to catch the speed often enough for a very fast updating display, and while I've got that line, it might be
possible to do something else with it later on.
Art.

True, but if you've used the diagnostics mode, you'll see that the data is only refreshed every second, ok when converting to analogue dials, but seeing it all the time will get frustrating as it won't be smooth.

If I were you I'd stick to decoding the speedo pulse input, would allow better output.

I'll find out how often my Mum's Toyota Echo updates.
I was only going to do it every half a second the other way.

I made a tacho for a motorise dskateboard that I used to
have that updated every pulse as you were saying before,
but the results were undesireable, the last two digits couldn't
even be seen because they were changing so much..
Art.

that can be fixed with some programming (a hysteresis function), for example.

if before_rpm is +- 10 of now_rpm then don't_bother_updating

@rt, good to hear that your making progress.

So what data line are you using ? is it 'speed in' to the cluster or 'speed out' from the cluster to ecu, bem & cruise ? or are you using the trip comp data line ?

Cheers.

I pulled my dash apart and connected a lead to the speedo out line,
then put it all back together only to find out it's not a data line..
just another pulsing output the same as from the BEM.
So I'm going to pull it apart again and connect to the trip comp data line (14).

BTW, I've had a talk to dang, and it appears that the speed data is
available four times per second. Have another look at the digital speedo in the odometer screen.. it's updating at about this rate, not once per second.

I have proven that the pulses do vary in length, but strictly speaking,
it's not a PWM signal. A real PWM signal has a shorter off time as the on
time increases. You can bring the car to a complete stop with the speedo
out line either live, or off.
Art.

The signal from the speedo (the actual geabox sensor) is just a square wave with a varying frequency. The faster the speed the higher pulses per sec the shorter the pulse width.

Instead of counting pulses per second measure the pulsewidth of the signal. It's much faster and if you dont want it to jump around just keep averaging the input untill it is updating as fast as you want.

What sort of micro are you using. I did this with a picaxe (see vehicle datalogger) but with no hardware access to the timers it was frustrating. My new micro can count these pulses in the background.

I wouldn't bother trying to read and decode serial comms from the car. Too hard and model specific. Just use the direct signal from the gearbox and it will work the best.

On another note the Vehicle datalogger V.2.0 is coming along nicely. It's not mounted in the car yet but bench testing and developing of software is moving along. I have all the timers set up and the analogue measurements (8 in total) are working. Including calibration tables to read coolant and temp (or whatever you want) sensors.

Currently working on the digital inputs/outputs. Hope to be able to measure: pulsewidth, Km/hr, duty cycle, RPM, frequency, digial MAP. with a very high accuracy.

It also has the 4x20 line backlit display, 38400 serial comms, and eeprom storage of 5min of data. .

Still a prototype but have located suppliers for the circuit boards and 90% of components. Should be very useful for ppl upgrading to programmable management. eg. can datalog injector Pulsewidth against RPM and load to determine the factory fuel mapping.

Will keep ppl informed.

Sorry for thread hijack!

f**k hell mna, thats a freaking aweosme effort.

Firstly, I would love to have this idea in my dash. Maybe situated inside the analogue presented speedometer.

Seocndly, what sort of background do you have in thsi stuff? Not being a smart a** but im curious to know how hard it is to do for Joe Citizen like myself.

Thirdly, I would turn this into a doco.

Keep up the awesome work amte. I didnt know half the stuff you guys are on about.

tested mine, stays the same all the time, 8 secs for slowest setting, stopped or 100kph .... had to get a new BEM a while back, should've got an EL one, wonder what else is different

and back on topic, i think it was a shame they dropped the digital dashes, the only b**ch i had with mine was the tacho, that was just a series of leds with a number next to it.., that was pretty crappy, but the speedo was great

at one time i had an after market digital clock that also had a tacho function as well (numerical display), i cut a part of the dash out in the car i had at the time and set this thing into it and it was great, easy to read and precsise

2 days to go on the eBay cluster with broken speedo, I hope I get it.



When I'm finished the software, I will draw a schematic, document, and provide the software so anyone
can make it. I'm not trying to make money out of it. I started out programming to help me steal
pay TV. I have no professional background with it.. or I'd have it finished by now
It does take some time to get a grip on assembler, but you can start with BASIC and go from there.



The EL smartlock document on this site covers that, it also has to be at least Futura I think...
"Mid Series Features (Red EF / Blue EL Colour)
The Mid series Body Electronics Module had all the features of the Low series, and additional features such as,
Dome Lamp Delay/Fade
Power Window Operation with Key off
Variable vehicle speed sensitive intermittent Wipe (EL Only)"


I would have finished it by now if I could use PWM, but since it's a multiplexed LED display,
It has to be constantly driven, If I timed a pulse it would make the display flicker at a rate that varied with the speed of the car,
and I couldn't handle that. I'm using a 16F84A for this, so I can use timer tmr0 in the background, or interrupts.


I'm going back to this way, with some good advice from dang who gave me an easier formula (2 in fact).
waiting around for serial data would also neglect the display routine.
Cheers, Art.

There is a schematic in my gallery of a simplified digital speedometer.
I used orange displays for this one since they closely match the colour
of the odometer in the cluster. Blue LED displays can be used with this
design.

Drop me an email if you would like to try the project, and I'll email you
d**k Smith/ Jaycar catalogue numbers for major parts, circuit notes,
and hex file for pic microcontroller. The cost of the bare electronics is
about $30.

Cheers, Art
art@austech.info

ps. If you don't have a pic programmer, and want to biuld the project,
I will send a pre-programmed microcontroller for a reasonable price.

I also have a completed unit that I am prepared to sell.
It has red displays, and will connect straight to an EF or EL Falcon
without the need for any adjustment. The unit is callibrated to the
digital speedometer that appears on the instrument cluster in
diagnostic mode.
Cheers, Art
art@austech.info