Alarm 12V Signal for GPS Locator input

hconceic

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I am fitting a GPS locator on my 2009 GS, that has an input for the alarm signal, theoretically activated by 12V, but I have tested it ok with as low as 4V.

The problem I am facing is to find a signal that turns on when alarm triggered.
I have disassembled the alarm, checked schematics and found the following signals pin out so far on the plug:
- 1: cannot find the meaning of this signal (sometimes close to 1V during alarm sometimes spikes of 5V
- 2: same as previous
- 3: reset signal coming from instrument cluster (i.e. ignition on)
- 4: 0V
- 5: CAN LOW
- 6: CAN HIGH
- 7: cannot find the meaning of this signal, sometimes 8V, sometimes 0V, sometimes 12V, when connected to locator input goes down to 0V
- 8: +12V

Can anybody help finding the meaning of these signals or where can I find a reliable signal that only goes on when alarm triggered?

Thanks a lot!
 
Maybe the signals are negative switching so that grounding the signal doesn't blow the alarm.

If they are you could try using a 10k ohm resistor, one end connected to +12v other end connected to the alarm. Volt meter between the alarm connection and earth should give +12v when alarm not sounding, and near 0v when alarm sounding.

Once you have checked that (at your own risk) can advise on how to invert the signal for your GPS.

** This is all guess work so at your own risk **
 
rce said:
Maybe the signals are negative switching so that grounding the signal doesn't blow the alarm.

If they are you could try using a 10k ohm resistor, one end connected to +12v other end connected to the alarm. Volt meter between the alarm connection and earth should give +12v when alarm not sounding, and near 0v when alarm sounding.

Once you have checked that (at your own risk) can advise on how to invert the signal for your GPS.

** This is all guess work so at your own risk **
Click to expand...

Whowww! I am afraid of trying that and damage the alarm or something else!
 
Ok, I am building courage to try the pull up to 12V.

Imagining that works, the 10k resistor would be constantly draining some current correct?
 
I am starting to think that I will have to find the alarm signal on the CAN BUS wires, but on the web could not find anything to decode that signal and generate 12V for my GPS input!
 
No luck with the 10k resistor ?

In theory depending on the alarm config the current draw should be pretty low, but first you need to decide if it is possible.
 
To be completely honest, I cannot find the courage to try it (12V on a PIN that is not documented anywhere sounds dangerous!).
Besides, that PIN 7 signal is always 8V on standby and during alarm keeps jumping from 8 to 12V (every 1s) so I find hard to believe it could come to 0V while pulled to 12V with a 10K resistor.
After investigating all the schematics I have (R1200GS-WD2.pdf) I start to think that the only way is to get some kind of electronics decoding the CAN BUS and outputting 12V when the alarm signal is on the bus. Googled a lot and could not find anything to do this, do you think such a thing exists?
 
These floating signals are quite likely to be data lines, and the odd voltages you see are pwm averages or aliased samples over the train of bits going by.

Can you get a scope on the job to verify if it's dc signalling?

You'll need some very low power micro controller that can be programmed to follow the conversation most likely, and drive your 12v to the end device.

It'll need a feed of clean stable power too, ironically.

Or there's things like ... http://www.stackltd.com/tdivmoduleg.html

You'd still need to register messages to look for to turn your widget on.
 
Last edited:
Many thanks ianf and rce, your knowledge is greatly appreciated!

Unfortunately I do not have a scope (will try to borrow one next week) but I couldn’t agree more with you, they really look like data channels.

Finding/creating the code and programming a micro controller might be just too much for my knowledge on the CAN BUS area and the Stack loggers too big and expensive!

I was looking for easy options, but maybe they do not really exist…yet.
It is still difficult for me to accept that there is no 12V (or other constant signal) activated during the bike alarm! This weekend I will try to find any “unused” signals on the Instrument Cluster plug... and get back with any findings.
 
You've had the alarm apart?

Where is the siren, in it? What sort of drive is there to it? That's likely to be a simpler signal to monitor.
 
ianf said:
You've had the alarm apart?

Where is the siren, in it? What sort of drive is there to it? That's likely to be a simpler signal to monitor.
Click to expand...

That's exactly what I did today, found the siren output to be around 5V and tested it to be enough to activate the GPS locator input… drawback is that it will trigger whenever the siren is activated even briefly, i.e. when you activate the alarm w/o the motion sensor (for transport) or when the alarm was triggered and you turn it off (on these situations the siren emits briefs beeps).

Also tried to find any unused signals on the instrument cluster plug but none.

In summary, if no better signal found (for weeks now that I am sleeping on the subject), I will go with the siren signal, just need to test if connecting the GPS locator input will not influence the siren sound output.
 
hconceic said:
To be completely honest, I cannot find the courage to try it (12V on a PIN that is not documented anywhere sounds dangerous!).
Besides, that PIN 7 signal is always 8V on standby and during alarm keeps jumping from 8 to 12V (every 1s) so I find hard to believe it could come to 0V while pulled to 12V with a 10K resistor.
After investigating all the schematics I have (R1200GS-WD2.pdf) I start to think that the only way is to get some kind of electronics decoding the CAN BUS and outputting 12V when the alarm signal is on the bus. Googled a lot and could not find anything to do this, do you think such a thing exists?
Click to expand...

Have you tried measuring the Hz across each pin. If they are CAN stacked messages and you tap into them with some devices it's possible the ECu will get crossed mixed messages and get confused and send you a light on your dashboard for engine management. Each message should have it's own frequency so it knows what it's receiving
 
hconceic said:
That's exactly what I did today, found the siren output to be around 5V and tested it to be enough to activate the GPS locator input… drawback is that it will trigger whenever the siren is activated even briefly, i.e. when you activate the alarm w/o the motion sensor (for transport) or when the alarm was triggered and you turn it off (on these situations the siren emits briefs beeps).

Also tried to find any unused signals on the instrument cluster plug but none.

In summary, if no better signal found (for weeks now that I am sleeping on the subject), I will go with the siren signal, just need to test if connecting the GPS locator input will not influence the siren sound output.
Click to expand...

So you need a timer circuit, that starts when the voltage rises, and needs more than the arm beep time or nudge beep time, before the output latches on.

Exactly what your generic 555 timer circuit is for, mono stable type usage on

http://www.555-timer-circuits.com/an-overview.html

Supply Input 4.5-15v output 0 or supply once timer goes off, as long as time >beeps you're set. Oh and you sure it's a dc signal yet?
 
JASONBC said:
Have you tried measuring the Hz across each pin. If they are CAN stacked messages and you tap into them with some devices it's possible the ECu will get crossed mixed messages and get confused and send you a light on your dashboard for engine management. Each message should have it's own frequency so it knows what it's receiving
Click to expand...

The CAN BUS pins are clearly identified and I am avoiding to mess with those (share your opinion) unless I would find a specific hardware to decode the alarm signal.
 
ianf said:
So you need a timer circuit, that starts when the voltage rises, and needs more than the arm beep time or nudge beep time, before the output latches on.

Exactly what your generic 555 timer circuit is for, mono stable type usage on

http://www.555-timer-circuits.com/an-overview.html

Supply Input 4.5-15v output 0 or supply once timer goes off, as long as time >beeps you're set. Oh and you sure it's a dc signal yet?
Click to expand...

Great idea, could even avoid SMS for those false alarms that we cancel after a few seconds when close to the bike!

Did some more investigation today but completely forgot to check if the siren signal is DC, probably not, to generate all the different tones… but will check it any way, during the week if I can find some time one of these evenings.

Thanks for the 555 timer circuit suggestion, I opened the link but definitely I am not comfortable designing a circuit for this and want to avoid at all cost any battery drain to power this circuit.
 
When projects get very hard/complex, I use to go back and recap from the beginning… By doing this, I remember that even before buying the locator, I measured on PIN 7 constant 0V in standby and 12V during alarm (main reason why I decided to buy it) but on the following tests I started to read 8V on standby and 8/12V on alarm… could it be that I have damaged this output with so many tests (eventual accidental grounding, static, etc)?

Can anybody with a BMW, CAN BUS and ALARM equipped measure the pin 7 on the DWA module?
 
Found this evening that the siren signal has 5VDC and around 80VAC!!! Hoops, hope I did not damaged the GPS locator input durign tests!

Also checked most of the ICs pins on the alarm circuit board and the most interesting signal came to be on the rear left corner with the following output:

During alarm
1.5 VDC
2.3 VAC

Durign chirp
0.36 VDC
0.99 VAC

This one looks safe to use with the locator input, but keeps sending SMS even during chirps.

The 555 timer IC looks complex to me, do you think there might be any other way to filter the chirp signal above?

Many thanks once again for all your great help!
 
Did some more investigation (I miss a garage to not have to disassemble and reassemble everything all the time) and found the following current info on PIN 7 (that I prefer as directly on the plug and no need for holes on the alarm box):
- On stdby: 0.85 microADC (direct or with 4.7 MOhms)
- During alarm: 1.36 microADC and 50 microAAC

I keep finding the same problem that is, no trigger of the locator during alarm (only triggers when connected for the first time and puling down the 8V to almost 0V).

The other thing is relative to voltage, when I connect a 4.7 MOhm resistor between PIN 7 and the locator the voltage drops to 2.7V and does not activate the locator.

Also measured the locator alarm input impedance: 50KOhm.

In summary, this PIN 7 has 8V on stdby, 12V during alarm and when connected to the locator (50KOhm or 50K+4.7M) the current is minimal and the voltage drops very close to 0V.

Should I try with a higher resistor?
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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