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A bit of background first. I'm running a delcoed EFI setup in my 1957 Chrysler Royal, Problem I have is I want to keep the original speedo which is cable operated. Im running a T700 trans so I have the electronic speedo sender feeding the ECU. Rather than buying T adapter to run both the cable and sender I was thinking of using a 12v motor to spin the speedo drive and set up a flex output to control the motor speed. Question is can I have KPH in both the X & Y axis in the flex table or would there be a better way of setting it up?

I cant see why not. You only need to make the 2nd axis 1 row large.

I was considering doing the same thing. Do you have an engine in mind that'll spin at the right speed with enough torque, and at low enough speed to do low kph? I purchsed one off the net, made it fit a gemini speedo but it was geared for 1000rpm I think, but when I hooked it up to 12v it didnt spin fast enough to get past about 80kph max.

The idea keeps floating around the back of my head though, but lately im thinking that the cleaner way to go might be a PWM controlled servo that can read the pwm for the angle, then remove the mechanical part of the speedo completely and mount the servo behind the guage face and stick the original needle on the front. Something like this would do it, although its designed to pull a lot more than a needle around.. theres also 'mystery' brand servos - $20 delivered for 6.. small, light, plastic gears not metal, but probably fine for a speedo needle only. Comes with various plastic mounts to fit the servo, so could cut one of them down and glue to the needle or similar.

http://www.youtube.com/watch?v=CPvnBTQBcmE

Has anyone tried anything like this?

MOPAR wrote:Question is can I have KPH in both the X & Y axis in the flex table or would there be a better way of setting it up?

Yeah can do, there is no limitation as to what is in each axis - can even have the output of one flex table as an axis of another if you want. In your case can have the other axis (say X axis) anything you want and just have each column filled with the same values, will be a 2D table then.

Ive just ordered a couple of these.
The item specifications.

* Size : 22.9x11.4x22 mm / 0.9x0.45x0.87 in
Voltage : 3v ~ 6v
Weight: 5g / 0.18oz
Speed : 0.10 sec/60(4.8V)
Torque : 0.8 kg-cm
Working Temp : -30C~60C
Teflon Bushing, 15cm wire, coreless motor
Servo arms & screw included

When they arrive I think i'll try and convert my mechanical speedo and tacho to ecu controlled. I currently dont have a speedo as I ran out of room in the trans tunnel to connect the speedo cable to the back of the electronic pickup!

Im thinking if I mount it so that no PWM signal causes it point to 0kph, then I can have a 2x1 flex table of kph vs kph and can realtime tune the PWM for the speedo high mark, and the ecu shouldnt push it past the limit no matter what, and if for some reason the ecu is off and the dash is live it should try to put the needle past the 0kph stop either.. Since the pwm scale should be even it wont need much of a table to be accurate.

i can see how this is going to work .... very interested to see on a tacho how lagged it is .... i know from my radio control experiences they are pretty fast to respond but just how fast is needed

I will have to wait and see how the guages motion looks with the available resolution of the PWM out from the ecu. I'll post up a vid when I have it working.

For general info on the subject of RC servos here:
http://www.societyofrobots.com/actuators_servos.shtml

antus wrote:
thinking that the cleaner way to go might be a PWM controlled servo that can read the pwm for the angle, then remove the mechanical part of the speedo completely and mount the servo behind the guage face and stick the original needle on the front.

RC servo, I like that idea. I looked at using the internals of an electronic speedo but it looked messy, never considered using a servo. My brothers got a heap of RC gear, might pinch a servo and have a play this weekend!

you could try fit the internals of a vl speedo onto your factory gauge panel gives you cable speedo and pulse output for ecu

Hi
Have a look at what this guy has done . http://members.ozemail.com.au/~brettsue ... /index.htm
I have installed a VP commodore speedo into my WB tonner with a few mods and the original facia using this guys ideas. Works great and is only reads 3 kilometers an hour slow.
Where he has changed the resistor on the circuit board put in a variable resistor instead to make calibration easier.
Then run the ECU using the pulsed output from the speedo.

Hope this helps
Cheers

Update: Not much luck with this. It turns out the servo is high side driven and the delco has a low side driver.. so needs something to invert the signal straight up. Then approx 2ms pulse width is 360 degrees, and thats at about 10% duty cycle, and the delco takes steps of 0.4% So you get 25 angles in 360 degrees that is approximately 14 degree steps. Its probably usefull for something, but thats what we have to play with.