Thread: Old car/engine, non ODB, how to get RPM/speed/temp/etc into carputer

Well, back in high school a few of the electronics students built Digital Dakota kits for their final project. Might have a look on their site here:
http://www.dakotadigital.com/
I know the speedo/tach combo was popular, and was not a very expensive kit. Here is the interface to go from a rotating speed cable to a signal: http://www.dakotadigital.com/Detail....umber=SEN-01-2. These are kits that are used to provide a digital dashboard, so maybe they are a step in the right direction for you.

Originally Posted by gospeed.racer

Well, back in high school a few of the electronics students built Digital Dakota kits for their final project. Might have a look on their site here:
http://www.dakotadigital.com/
I know the speedo/tach combo was popular, and was not a very expensive kit. Here is the interface to go from a rotating speed cable to a signal: http://www.dakotadigital.com/Detail....umber=SEN-01-2. These are kits that are used to provide a digital dashboard, so maybe they are a step in the right direction for you.

Check these out ...

Thanks for that link, gospead.racer Looks like it might be a "failsafe" option if all else fails

Anyways, from a little googling, I was able to find this. On that page, is linked to the mini-datalogger pic below:



If my guesses are correct, then the tach, petrol level and temps are just voltages passed to the stock guages (they're just 2 wires into the back of each, i'm guessing a signal, and a common ground). Of course, this is all basing it on the fact that all the guages work on variable voltage depending on their status.

With 8 inputs via this, and the VVIO.dll code for C and VB, as well as DOS and Linux, it's looking quite interesting.

Then the only other thing will be some way to get a linear voltage from the speedo cable coming from the gearbox. Possibly a high sensivity dynamo? Any ideas on this one?

Some good info coming in now


Garry

Confused,

I am also interested in this. I would be very curious to see how you solve this. Please keep us all up to date as too how you proceed with this. I have an old Alfa Romeo and would like to get these features on screen.

Thanks,
Simon

tach will be a pulse out from a/the coil, gas is usually a resistance,speed is also probably a pulse and other may be voltage or resistance.

The tack will be a pulse ,so "just" use a freq/volt converter;the speed is for many cars e magnet turning round and "dragging" the speed needle with it,so a hall contact and a freq/volt should do.
I am planning to use the hall contact with a PIC to drive a stepper motor to move the speed needle to get a precise speed

Right, i've got some more information (from my dad) which should help a little This is just me putting my thoughts down so they might not be in any good order, or make too much sense...apologies for that

Right, firstly, fuel level/temperature(s). Most older cars have a regulator, which goes through the needle, to the reciever, which goes to ground. The reciever works on changing resistance. Therefore, all you need to do is keep the current stuff, and measure the voltage change in the needle due to the differing resistances from the reciever.

For tach, it does indeed work on a pulse from the engine. For my car at least, this pulse is put through a small chip/circuit in the tach housing itself, which converts this pulse into a voltage, which is attached to a small motor which turns the needle to where it needs to go. As this last bit is working on voltages, you can keep the circuit board, and remove the motor/needle part of it, and measure this. I am not sure as of yet whether this will be linear or not...but the software part of it should be able to cope with that (well, i'm hoping anyway )

For speed, that is a cable which, as mst said, "drags" the needle round. This is the bit that I'm not too sure about...mst, maybe you could help/provide more information on how a differing voltage can be read from this??

However, before I can really start on this, I need to get my engine rebuilt and up and running, preferably in the car That will take me a couple of months I guess, given the weather (well, the lack of good stuff) and temperature (or, again, lack of)


Garry

Well,sorry but my knowledge is only theoretic,for the time being,from "the microcontroller application cookbook"by Matt Gilliland:there are two types of Hall-effect sensors:linear and digital.In the linear the output voltage is proportional with the revolution;the digital measures the revolutions direct.I will try to scan the pages from the book and PM then to you,he explains it better then me(there are even some schematics)

Cheers for that, mst

I haven't even heard of Hall-effect sensors...so anything I learn about those is a bonus


Garry