Golf mk7: Auto Start/Stop disable switch - who wants to help?

[AJW]

AJW - looks like you're using Eagle there. Any chance I can get my hands on your files and a BoM? I'd be happy to have a set of PCBs made using OPSHPark (cheap enough that making boards at home is just not worth it anymore) and to assemble a few test units (I have reflow gear).

Actually I'll extend my offer to both you and DV52. Happy to self-build any prototypes you guys come up with.

Yes I'm using Eagle to make the PCB. No problems sending up the finished PCB design if you want to make one.
I did the circuit in a separate program so I've only got the PCB layout.
I'll wait until I get my car before I send up the file as I'm not 100% sure it will work yet and I may need to do some mods.
I've sourced all the bits from Element 14 - will give all the part numbers when I know it's working.

My plan was to connect directly across the switch and use the Cigarette lighter socket for power - It seems to be fairly close.
The hope is the Cigarette lighter comes on when then the car is started, then the circuit starts it's ~10secs run to then send a signal for 1 sec to cause the Photomos Relay to pull the contacts of the switch to ground and hence turn off the S/S.

If someone has a car can you check how the Cigarette lighter operates? I know in the MK6 there was a 50min? timer to keep power to some of the circuits, say if you turned the radio on with the key out but door open. I'm not sure what else they might be doing in the MK7. My new car will also have Keyless Entry so again I'm guessing pushing the Start switch is exactly the same as turning the Ignition switch?

[mattaus]

Yes I'm using Eagle to make the PCB. No problems sending up the finished PCB design if you want to make one.
I did the circuit in a separate program so I've only got the PCB layout.
I'll wait until I get my car before I send up the file as I'm not 100% sure it will work yet and I may need to do some mods.
I've sourced all the bits from Element 14 - will give all the part numbers when I know it's working.

My plan was to connect directly across the switch and use the Cigarette lighter socket for power - It seems to be fairly close.
The hope is the Cigarette lighter comes on when then the car is started, then the circuit starts it's ~10secs run to then send a signal for 1 sec to cause the Photomos Relay to pull the contacts of the switch to ground and hence turn off the S/S.

If someone has a car can you check how the Cigarette lighter operates? I know in the MK6 there was a 50min? timer to keep power to some of the circuits, say if you turned the radio on with the key out but door open. I'm not sure what else they might be doing in the MK7. My new car will also have Keyless Entry so again I'm guessing pushing the Start switch is exactly the same as turning the Ignition switch?

Don is sending me the parts for his design so I'll be able to say what does and doesn't work sometime next week. I am using the cigarette lighter for my initial tests, just to see if the device acts as expected. You are correct that the 12V socket comes on only when the car starts, but I cannot comment on the 50min timer or anything else just yet. From my brief research I know some people have changed their fuse settings so that the 12V socket is permanently powered which will cause issues for your install (but only if you had the permanent 12V mod done). For my permanent install (provided it works!) I'll be using a fuse tap and will install the device in the fuse box.

More mucking around, and more pieces to pull, but it means the 12V socket will function as it does from the factory. This also means that if I ever decide I need permanent 12V source, I can easily change the fuse for that without screwing up my S/S changes.

[DV52]

If someone has a car can you check how the Cigarette lighter operates? I know in the MK6 there was a 50min? timer to keep power to some of the circuits, say if you turned the radio on with the key out but door open. I'm not sure what else they might be doing in the MK7. My new car will also have Keyless Entry so again I'm guessing pushing the Start switch is exactly the same as turning the Ignition switch?

AJW: The ciggy lighter socket (I think that the more PC term for this item is "Power Socket") can be modified to do both functions (i.e. "hard 12V", or terminal 15). See my thread HERE. But as a factory default, the ciggy lighter is a terminal 15 supply.
Don

EDIT: oops- sorry Matt, you got-in before me

[DV52]

Don is sending me the parts for his design so I'll be able to say what does and doesn't work sometime next week. I am using the cigarette lighter for my initial tests, just to see if the device acts as expected. You are correct that the 12V socket comes on only when the car starts, but I cannot comment on the 50min timer or anything else just yet. From my brief research I know some people have changed their fuse settings so that the 12V socket is permanently powered which will cause issues for your install (but only if you had the permanent 12V mod done). For my permanent install (provided it works!) I'll be using a fuse tap and will install the device in the fuse box.

More mucking around, and more pieces to pull, but it means the 12V socket will function as it does from the factory. This also means that if I ever decide I need permanent 12V source, I can easily change the fuse for that without screwing up my S/S changes.

Matt/AJW: I've had a close look at VW's wiring diagrams for the centre console portion of the vehicle. After piecing together a number of pages, I believe that there could be a more convenient location (than the ciggy socket) as the source for the Terminal 15 supply.

Here's what I have put together from my research (please note that I have removed all other wires from the wiring diagram that I didn't consider relevant to your project):

As you can see the crucial new piece of information concerns the wire that begins life as a connection to what VW call the Relay for Power Sockets. These aren't the sockets that we call ciggy sockets, but rather this is the relay that supplies terminal 15 supply to a number of take-off points on the loom inside the cabin (for stuff like the internal mirror, air quality sensor and the ciggy sockets - notice the supply to the relay comes from fuse #40 which is the same fuse as in my thread on how to make the power ciggy socket a "hard" 12 volt supply)

Anyhow, the wire of interest terminates on PIN#10 of a 10PIN connector on Switch module 1 in the centre console. In an amazing coincidence, this is the same switch module as the one that contains the native S/S disable switch. How handy is that?

I'm not sure if the pin numbers are shown on the switch module but it doesn't matter because all you need to do is to look for the Black/Yellow wire. Even if your car doesn't have a TCS/ESP button, I'm hoping that the Black/yellow wire is present. In fact, there should be a bunch of other of places where the Black/Yellow wire takes Terminal 15 supply. If you find this wire anywhere in the area where you are working, it's likely to be a Terminal 15 supply.

To confirm the wiring diagram, you might want to check the voltage dynamic on this wire with the ignition switch on/off using a multimeter before you start splicing a new connection

Good luck
Don

[mattaus]

Don. Brilliant! Certainly sounds a lot easier than what I had in mind. Hopefully the wire is where you say it should be

I was going to pull my console apart tonight to have a look in there, but to be honest I'd prefer to do it once and once only if I can help it. Thus, I will wait until I have a unit in my hands to test with. I think once I've seen the parts I will just wire it all up as small as possible; that way it will fit regardless, or not fit all. If that makes sense.

[mattaus]

OK, so needing to kill time before I headed off to the gym I did go and have a fiddle (stop sniggering in the back).

I'll take better photos (during the day would be a good start) when I do an actual full install guide.

The good news! The pins are marked (forgive the ****ty camera):



And low-and-behold there is a yellow and black wire connected to socket 10. I was unable to test the voltage on this because I did not have a lead for my DMM small enough to fit anything. I'll have to raid my electronics box for something that will work.

Now the switch cluster itself looks like this:



I'm hoping Don's plan involves wiring into the plug that goes into the bottom of the 3 switch cluster rather than the actual S/S switch itself, because bugger me if I could get the cluster apart. I'm sure it's possible but this stuff is fragile and I do not want to snap something 10 day old car just yet!

My thoughts are that there will be no need to pull the switch assembly apart because one of those 10 sockets on the wire harness will surely be responsible for sending the ground signal back to the brains? It's likely obvious from the diagram's Don has already included but I'm in a hurry and just wanted to get this up before I had to leave for a few hours. Hopefully the brains trust will have answers for me when I come back

Sorry if this doesn't really tell us anything helpful!

- Matt

[DV52]

OK, so needing to kill time before I headed off to the gym I did go and have a fiddle (stop sniggering in the back).

I'll take better photos (during the day would be a good start) when I do an actual full install guide.

The good news! The pins are marked (forgive the ****ty camera):



And low-and-behold there is a yellow and black wire connected to socket 10. I was unable to test the voltage on this because I did not have a lead for my DMM small enough to fit anything. I'll have to raid my electronics box for something that will work.

Now the switch cluster itself looks like this:



I'm hoping Don's plan involves wiring into the plug that goes into the bottom of the 3 switch cluster rather than the actual S/S switch itself, because bugger me if I could get the cluster apart. I'm sure it's possible but this stuff is fragile and I do not want to snap something 10 day old car just yet!

My thoughts are that there will be no need to pull the switch assembly apart because one of those 10 sockets on the wire harness will surely be responsible for sending the ground signal back to the brains? It's likely obvious from the diagram's Don has already included but I'm in a hurry and just wanted to get this up before I had to leave for a few hours. Hopefully the brains trust will have answers for me when I come back

Sorry if this doesn't really tell us anything helpful!

- Matt

Matt: Clearly I have chosen the correct co-inventor. As a well known Jedi gnome once said "strong with this one - the enthusiasm is"!

On a more serious note. Just get hold a couple of sewing needles and shove them into the connector space, attach the multi-meter leads to the bits that stick-out! I agree with your method of approach - better to connect to the back of the switch module.

If you look at my post#1, you will see that the signal wire to pin #4 is black/blue. You should see this colour wire in the rear of the connector loom (on the opposite side to the Black/Yellow wire.

If I could be so bold as to suggest a simple test before you connect the S/S kill switch to the Black Blue wire . Using those sewing needles that I mentioned earlier, pierce the Black/Blue wire with the sewing needle so that the tip goes through the copper wire. Then hook-up the multimeter leads to the needle-end and the other lead to an earth point. With the multimeter on DC volts, then press the VW S/S button and check that you have a short to earth. If you get this short every time that you press the S/S button, you have the correct wire. Incidentally, I have no idea what voltage the multi-meter will read with the S/S switch not depressed - please tell me
Cheers
Don

[pipedwho]

If you want a simpler install, consider using the pull up resistor on the button into a diode (and series resistance if necessary) to charge up a reservoir cap for the microcontroller supply. The micro and a drive FET should take very little power and the cap should still have sufficient charge to free wheel while the pull-up is being shorted closed.

[mattaus]

Matt: Clearly I have chosen the correct co-inventor. As a well known Jedi gnome once said "strong with this one - the enthusiasm is"!

On a more serious note. Just get hold a couple of sewing needles and shove them into the connector space, attach the multi-meter leads to the bits that stick-out! I agree with your method of approach - better to connect to the back of the switch module.

If you look at my post#1, you will see that the signal wire to pin #4 is black/blue. You should see this colour wire in the rear of the connector loom (on the opposite side to the Black/Yellow wire.

If I could be so bold as to suggest a simple test before you connect the S/S kill switch to the Black Blue wire . Using those sewing needles that I mentioned earlier, pierce the Black/Blue wire with the sewing needle so that the tip goes through the copper wire. Then hook-up the multimeter leads to the needle-end and the other lead to an earth point. With the multimeter on DC volts, then press the VW S/S button and check that you have a short to earth. If you get this short every time that you press the S/S button, you have the correct wire. Incidentally, I have no idea what voltage the multi-meter will read with the S/S switch not depressed - please tell me
Cheers
Don

Co-inventor? Mate, I'm the guinea pig!!!

Fortuitously one of my failed attempts to photograph the plug numbers shows the black and blue cable of wonder:



So my plan of attack once I have the parts will be to:

1. Needle in the BY wire and and a needle in the GND wire (pin 1) to test the voltage supplied by the BY wire.
2. Another needle in the BB wire along with the one already in the GND wire to test for a short to earth. I will hopefully remember to report back the resting voltage.
3. Attach the S/S device to the 3 needles and see if it works when I start the car.

The switch cluster will be plugged in the entire time. It may be tricky because there is almost no slack on the wire loom, but I'll try my best.

If you want a simpler install, consider using the pull up resistor on the button into a diode (and series resistance if necessary) to charge up a reservoir cap for the microcontroller supply. The micro and a drive FET should take very little power and the cap should still have sufficient charge to free wheel while the pull-up is being shorted closed.

Is this in reference to Don's design, or AJW's? Or am I missing the mark entirely lol?

[DV52]

Matt: I think what pipedwho is suggesting is to create a parasitic (low) power drain into a low loss capacitor from the signal on BCM PIN#60. The capacitor acts as an energy storage device and it becomes a power supply to run both a microprocessor and the FET switch that I posted earlier.

The micro would be programmed to produce the correct timing pulse to short PIN#4 on the switch module. Because the establishment of the parasitic power supply is self regulating for the Auto S/S kill switch, there would be no need for the 5 sec time delay in my design (and the delay in AJW's circuit). The duration of the actual S/S kill pulse would need to be carefully chosen bearing in mind the limited energy in the capacitor (unfortunately the S/S kill signal would also short-out the parasitic power supply - with the diode free wheeling as pipedwho says). Plus there would only need to be two wires in the Auto Kill switch.

What a truely inspired and sublimely elegant suggestion! Pipedwho's idea places the Auto S/S kill switch more intimately into the electrical operation of BCM signal. But the crucial bit in pipedwho's suggestion is (I think) that success of the circuit depends on being able to fool the BCM into believing that the parasitic current drain isn't happening.

Problem is that I just don't know anything about the electrical characteristics of the signal from BCM PIN#60. This is the same problem that exists with both my and AJW's design (sorry pipedwho - this isn't meant as a criticism, its just a statement of fact).

But, I think that pipedwho's suggestion is an intellectually superior and a much better engineered concept (than my clunky design). And it would be easier to install. It just needs more time and more R&D than I have available - but perhaps another forum member could pick-up this baton and run with it?

Fact is that there is no right solution to this problem - there are just different solutions

Don