This is a project that I've made for a former car, VW Passat 3C (B6). It will apply to every car of the mentioned model manufactured until 2009. For cars newer than 2009 is no longer needed as this functionality was embedded in the car board computer.
One of the things that bothered me was that the AutoHold function had to be manually started by pushing the AH button near the gear shifter, each time I started the car, because my car was of a pre 2009 make.
To solve this problem and make the AutoHold function start as soon as the car is started and conditions fulfilled (seat belt ON, driver door closed), a few years ago I made this project.
It will require to remake the connections on the AH button (easy task as they are only 2 wires that need to be cut and one wire needs to have the isolation stripped back).
The power needs to be taken from a +12V connection that is ON while the car is started. This is so the module will not consume power while the car is OFF. This can be found on pin 20 from the Climatronic module (that wire needs to have the insulation stripped and then a connection can be made there).
I made a document with instructions and it can be found in the folder Documentation
in the archive.
The name of the file is: Install instructions.txt
In the archive you will find:
- a PCB project made in Altium Designer 16.1.9
- GCODE drill file (drill at -2.7mm depth, travel depth at 2.5mm, feedrate: 300mm/min, drill change position: 30mm at origin point, it will also help in making zero for the drill by using several STOP commands - you need to press START in Mach3 to go next step).
- simulation in Proteus 8.4
- PDF files for negative transparency films needed for UV exposure; one for copper and one for soldermask. Each file has the pattern duplicated as this may be needed to achieve good opacity for the black regions.
- the firmware project made in MPLABX + XC8 1.37 PRO
The board is made in dual layer but all the traces are on the bottom layer so you can easily make this board on a single layer PCB board. Most of the parts are through hole but there are some 0805 SMD's on the bottom layer.
In the documentation folder you will find a 3D PDF file so you have an idea of how the board will look like.
All the parts have an 3D body added and for each part you will have a property named DIGIKEY# with the part number for that part from Digikey. Of course you can use other sources but they are given so you can start the project.
This is a picture of the board in 3D:
This is the schematic:
And this is a picture of the PCB: