Induction sensor wave signal , converted to hall effect sensor square wave...

Thread Starter

eXe

Joined Jun 25, 2017
25
Hi guys!
First of all, i have to mention that im more into automotive than electronics, and for this reason i end up here asking for and advice, opinion.

Ive changed an automatic transmission into a audi a6, but didnt know that the only difference betwin the two gearboxes (original and the new one) will be the transmission speed sensor... Now that i got it mounted, wich its quite a bit of strugle by the way, im tryng to figure out a way to make it working instead of having to change the entire gearbox again...
the original gearbox had an hall effect speed sensor, and the other gearbox that ive fit in, has an induction speed sensor

Offcourse, for this reason, the car isnt working... as soon as it changes to the second gear, it comes with and speed sensor error and it gets into emergency mode...

What i want to do, would be to find a way to cheat the signal, and make the transmission computer receive the correct information...
The biggest problem i have, its that im not that good with creating circuits from scratch ... If im guided , off course i can do it...

If someone its willing to help me sort this one out, will be very gratefull

If any other info needed, i can suply it without problem..

Thank you all in advance!
 

BR-549

Joined Sep 22, 2013
4,928
First.......you will need to determine the ratio that the original sensor was measuring.

Then determine the room and area for detection of/in the new unit.

This will help determine the correct sensor to custom employ.

I believe the best solution.......is to try to use the original sensor........customized to your new gearbox. Will save loads of work.
 

Alec_t

Joined Sep 17, 2013
14,313
Welcome to AAC!
This would be relatively easy to do with an analogue circuit if the number of pulses from the two sensors is exactly the same (for a given shaft rpm), but would involve digital processing (or more complex analogue circuitry) if they don't match.
 

Thread Starter

eXe

Joined Jun 25, 2017
25
Hey! really surprized of such quick reaction guys :)

I have investigated, and both gearbox internal's are the same... so they read out the same number of pulses, the only difference would be that one its inductive and the other hall...

@BR-549 : If by sayng "try to use the original sensor........customized to your new gearbox" you mean tryng to fit the original sensor into the new gearbox, i have think about that, but obviously the main issue will be that the hall sensor will not be able to read from the fly wheel... fly wheel wich its designed differently from the original one...
Someone sugested that it should work if i could be able to simply swap the fly wheel from one gearbox to the other one... but in order to do that i would need to remove the gearbox from the car. thing that i really try to avoid.

Other crazy ideea that crossed my mind ( please don't laff if possible) would be to use the induction that's allready inside the gearbox, wich its generating arround 2V , somehow amplify that 2V and than create an micro electro magnet and stick that on the hall sensor, wich hopefully would be able to read the magnetic impulses and transmit it to the gearbox computer...
Hope it doesn't sound way to crazy.... Off course i didnt try anything just yet... I allways prefer asking before, most because i know my limit's when it comes to circuits and stuff...
 

BR-549

Joined Sep 22, 2013
4,928
Have you got a scope?

Compare the signals.......you might luck out......and find a simple solution.

Compare the pulse count, polarity, amplitude, shape and duration.

If you were sensing the flywheel..........does flywheel have same number of poles?
 

Thread Starter

eXe

Joined Jun 25, 2017
25
No i didnt got that fare.... Also i don't have a scope... I'm thinking to get one if needed ...
 

crutschow

Joined Mar 14, 2008
34,413
You really need to find the difference between the two signals to determine what needs to be done.
You probably need a scope for that.
 

Alec_t

Joined Sep 17, 2013
14,313
So, to confirm, you want to take the signal from an inductive sensor and turn it into something resembling the output of a Hall sensor?
Does the Hall sensor provide a signal which flips between 0V and 5V?

Edit:
It looks like the Bosch Vss Hall sensor has an open-collector output which can sink 10mA.
 
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BR-549

Joined Sep 22, 2013
4,928
ok.......I am not an expert......am just going by what fundamentals I know. You will have to find out the electrical specs of the two different sensors. and we will have to know what signals the controller expects from the sensors. with that info....we can suggest solutions.

The sensors data sheets and car's electrical manual would be handy.

Even in the worse case.....there are experts on here that are familiar with your setup.

It's like fishin........a little patience.
 

crutschow

Joined Mar 14, 2008
34,413
The inductive sensor may not be outputting the correct voltage (or proper waveshape) for the computer input.
If so, a simple comparator circuit that converts the sensor voltage signal into a square-wave may solve the problem.
 

Alec_t

Joined Sep 17, 2013
14,313
You may get away with something as simple as this :
SensorAdaptor.PNG
This has an open-collector output and responds to a bipolar input of ~0.6V amplitude or greater (typical of an inductive sensor output, from what I see on the web).
It works for a 5V or 12V ECU rail.
 

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crutschow

Joined Mar 14, 2008
34,413
You may get away with something as simple as this :.......
That should work.
And if you use an actual transistor model instead of the default model, the waveform actually improves with a duty-cycle closer to 50%:
upload_2017-6-25_12-5-50.png
 
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Thread Starter

eXe

Joined Jun 25, 2017
25
Guys, i had to run out at the garage for a while... Can't believe the quick responses ! I'm browsing several forum's for quite a while now, but never saw such quick reactions... For this i really wish to THANK YOU so much!

Now for the schematics... which one should i start building , and really sorry for being dumb, but in the schematics you posted, the C1 its 33 μ or 33 μF ? Than what Q1 stands for? and the last, what is NPN for... i believe i should alocate more of my time learning the electronic basics , instead of doing mechanics :)

I have a breadboard , would that help me test it before actually start soldering?
If this will work, i will know it right away, i have a VAG COM scanner, wich can read live data from the transmission... That untill will get myself a scope.
 

Thread Starter

eXe

Joined Jun 25, 2017
25
Hi @LesJones ! Thank you so much for pointing that thread !
Its actually very similar problem, but so different in the same time... He tryes to fit new parts into the car while im just hopping to get this unique sensor being read by the TCU (transmission control unit)
Yes looks similar but actually isnt... But thank you very much for that... At least now i know im not the only one with this kind of issues...
 

crutschow

Joined Mar 14, 2008
34,413
Now for the schematics... which one should i start building , and really sorry for being dumb, but in the schematics you posted, the C1 its 33 μ or 33 μF ? Than what Q1 stands for? and the last, what is NPN for
Yes, μ stands for μF.
C1's value is not critical and can be anywhere from 10μF on up.

In my post #12 I show a 2N3904 but it can be just about any small NPN transistor, such as a 2N2222, 2N2219, BC547, etc., also.

Bipolar transistors come in two polarity types, NPN and PNP.
NPNs require a positive collector-emitter voltage and PNPs require a negative collector-emitter voltage for proper operation.
 

Thread Starter

eXe

Joined Jun 25, 2017
25
I don't think ive mention a little thing... The Hall sensor that my car has originaly, its being powered with 10.2 V by the ECU... Im sayng this because im not quite shore i understand how this will work in the end...
Basically the ECU send's out an 10.2V and the induction sensor curently into the gearbox, it produce arround2.0- 2.5V
Isnt there an issue when this two voltages meet?
This is actually the point i got stuck in the first place...
If i create this little board, will have to place it betwin the induction sensor, and the ECU... So basically the hall sensor its being replaced by this board... Am i getting it right?
 
Here's https://www.melexis.com/-/media/files/documents/datasheets/us5881-datasheet-melexis.pdf a Hall Effect switch. There are differences. What i wanted to point tout is that the supply voltage is wide range.

It's output is EFFECTIVELY a CONTACT CLOSURE to ground. So, if the ECM has a 5V supply, it's likely that there is a resistor between 5 and the hall effect switch. There could also be a resistive divider there as well. So, the ECM can see any voltage from it's logic supply (5 or 3.3) as a high and something close to 0 V as a low.
 

crutschow

Joined Mar 14, 2008
34,413
Isnt there an issue when this two voltages meet?
This is actually the point i got stuck in the first place...
If i create this little board, will have to place it betwin the induction sensor, and the ECU... So basically the hall sensor its being replaced by this board... Am i getting it right?
Yes.
The circuit takes the inductive sensor signal and converts it (hopefully) into a signal similar to the Hall device that will be recognized by the ECU.
 

Thread Starter

eXe

Joined Jun 25, 2017
25
So the only thing now its to get it done, at least on a breadboard, and try it, see how close i can get... Its kind of silly not having an oscilloscope... will try to get or borrow one asap...
@crutschow : will go for your schematics , and will report back

Thank you all very much!
 
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