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Old 07-01-2020, 12:56 AM
imqiu imqiu is offline
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Mein Auto:
DIY HOW TO: Hands free for Driving assist.

Hi everyone,
Here’s a solution about how to fool the touch sensor in the steering wheel if you have professional driving assist.

Disclaimer:
This discussion here is for research and testing purpose only. The author and the website do not take any responsibility for any results.

Theory:

The touch sensor unit in the steering wheel use a capcacitive way to detect whether your hand is on the steering wheel. The value of capacitance on the steering wheel rim was keep on changing, so the software in the touch sensor unit will adapt the lowest capacitance as the default value (as “untouched”), as long as it do not fall under certain threshold, otherwise the unit will throw a “Internal fault” error to the LIN bus. Meanwhile every time we turn off & on the car, the unit will do a self calibration to forget about the last lowest value of capacitance.
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Now here’s the way: We can insert a wire which is longer than 50mm (may be shorter can do the job, but it may trigger a “internal fault”) between the unit and the capacitive mat. A micro switch is need to temperately disconnect the mat (or anything you can make the connection&disconnection easily).
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1.When we first start the car, the sensor unit will calibrate the total value of capacitance of the wire + mat as default (“not touched”).
2.Then we pull and hold the trigger ( for one second) of micro switch to disconnect the mat, the 50mm long wire still provides a low value of capacitance for the unit to adapt as default(“not touched”).
3.Then we release the micro switch trigger to get the mat connected, the higher value of capacitance comes back and the unit will recognize this value as ”touched”.

By now we have successfully fool the sensor unit and enjoy the hands free all day long before you turn off your car.

Here's some picture of my mod:
Connect the wire to sensor unit
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The micro switch can be installed under the steering wheel
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Another Option:
If you are looking after a fully automatic solution for hands free, look at this HOD emulator here, they've done a fantastic work. https://www.bimmerfest.com/forums/sh....php?t=1382749 It works on F gerneration, but not sure the G generation shares the same LIN protocol.
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driving assist, hands free, hod, hoo


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