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resistor based door triggers


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freqsounds 
Copper - Posts: 289
Copper spacespace
Joined: October 17, 2008
Location: Virginia, United States
Posted: January 16, 2014 at 4:28 PM / IP Logged  
KPierson wrote:
Can you just monitor a dome light?
I could, but my dome lights stay on for 60 seconds after the doors are closed. It would cause a 'door open' error on the alarm if I arm right away. Although, it would give myself enough time to have a cigarette before I get to where I'm going! :)
I'm thinking the proximity sensor would probably be my easiest option. I can always go back and try to build the circuit later, but this would take care of things until I get a chance to play with the circuit.
No question is stupid or not worth asking. You were once a noob, right? :)
KPierson 
Platinum - Posts: 3,527
Platinum spaceThis member consistently provides reliable informationspace
Joined: April 14, 2005
Location: Ohio, United States
Posted: January 16, 2014 at 9:13 PM / IP Logged  
You can turn off that zone tripped warning beep.
Kevin Pierson
freqsounds 
Copper - Posts: 289
Copper spacespace
Joined: October 17, 2008
Location: Virginia, United States
Posted: February 03, 2014 at 4:28 PM / IP Logged  
KPierson wrote:
Can you just monitor a dome light?
I could, but the lights stay on for 60 seconds after the door is closed. I really wish the DBALL would work since it's a GM-manufacturered car... I thought about hooking it up, but didn't want to chance it.
No question is stupid or not worth asking. You were once a noob, right? :)
freqsounds 
Copper - Posts: 289
Copper spacespace
Joined: October 17, 2008
Location: Virginia, United States
Posted: February 03, 2014 at 8:00 PM / IP Logged  
Alright, so I was able to study all this context as I was snowed in all week last week. After 3 trips to the electronics shop, two circuit boards, and two soldering iron tips, I was able to get it working!
I attached a schematic of what I used. Please keep in mind this is my first schematic, and some info may not be 'standard' or 'correct'.
I had to put the threshold voltage on pin 4, and the input on pin 5. The reason is because if a door is opened, the voltage will drop to 4.1V. If all the other doors were closed, it would keep ground on the outputs. So by flipping the polarity on the LM339's inputs, the outputs will see ground when the voltage drops below the threshold.
In addition, I couldn't diode isolate all 4 doors into one input on the LM339. The reason is because with all doors closed, it would show 7.4V on the input. If a door was opened, that door would drop to 4.1V, but the other 3 doors would remain at 7.4V, and the highest voltage wins. Simply put, the voltage would never fall below the threshold unless all doors were opened at the same time.
In my schematic, I added an LED to the circuit. This will allow me to see at a glance whether the zone is triggered. According to the Service Manual for the Saab, the hood and trunk pins work the same way -- resistance based triggers. So I used a second LM339. As you stated, the unused inputs need to be terminated to eliminate false readings. So because we inverted the polarity of the inputs, I wired up a 10k resistor to the +12V instead of GND (not sure if the resistor was actually required though - it worked with or without).
Alright, back to the LED. With 3 separate triggers in this module, each output was spliced and diode isolated to the LED (if that makes sense). The (+) side of the LED to direct +12V, and the GND to the anodes of the diodes. This way if a zone is triggered, the door, trunk, and hood don't all trigger at once.
I tested the circuit as I was building it using a battery charger at 2A.
I haven't put it in the car yet, but I'm pretty confident it will work. I tested using a potentiometer on each input of the circuit.
Thanks for everything guys! I'm glad this was able to work out, because this proximity sensor has been going off every night a cat crawls under the car. Neighbors are pretty mad! xD
resistor based door triggers - Page 2 -- posted image.
resistor based door triggers - Page 2 -- posted image.
resistor based door triggers - Page 2 -- posted image.
No question is stupid or not worth asking. You were once a noob, right? :)
freqsounds 
Copper - Posts: 289
Copper spacespace
Joined: October 17, 2008
Location: Virginia, United States
Posted: February 09, 2014 at 11:52 PM / IP Logged  
Hey guys, I think I'm back to the drawing board on this one. I put the circuit in the car and it works great! For the first 10 minutes...resistor based door triggers - Page 2 -- posted image.
What the service manual doesn't tell you is that the BCM cuts off the voltage on these switches after 10 minutes. When metering, the lines are dead, around .3V until the BCM 'wakes up'
So, other than taking a before-and-after reading on the resistors, is there any way I can just detect the resistance itself where voltage isn't a factor?
I smell a new circuit! resistor based door triggers - Page 2 -- posted image. lol
No question is stupid or not worth asking. You were once a noob, right? :)
freqsounds 
Copper - Posts: 289
Copper spacespace
Joined: October 17, 2008
Location: Virginia, United States
Posted: February 11, 2014 at 2:04 PM / IP Logged  
*bump* Anyone?
No question is stupid or not worth asking. You were once a noob, right? :)
oldspark 
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: February 11, 2014 at 5:50 PM / IP Logged  
That means disconnecting at least one end of the resistance and measuring it - ie, injecting your own voltage and measuring the current. So forget that...
You need to use a mechanical solution - ie, tap into whatever switch it is that switches the resistors and see if that's closed or open. That too can be tricky unless its a grounding switch, but it's easier than measuring resistance.
Any chance of fitting an optic or micro switch etc to whatever moving parts are involved?
freqsounds 
Copper - Posts: 289
Copper spacespace
Joined: October 17, 2008
Location: Virginia, United States
Posted: February 11, 2014 at 6:26 PM / IP Logged  
That's what I was thinking, and it'd have to be for each door. Sounds like too much work haha!
I have been thinking about it all day today. I wonder if I can find a +12V wire that shuts off at about the same time the door voltage does. If so, I can use a relay to turn off the circuit to the alarm. Since the car knows when that door opens and wakes the BCM, I'm thinking it might just work, especially if I put a time delay to the LM339 circuit card. Does this sound like something that might work?
Unfortunately, these door latches are sealed with rivets. I'm afraid to pull it apart lol.
I was checking out the entire schematic for the central locking system, and everything ties into the CIM (Column Integration Module). I was thinking of pulling it apart to see if there's a 'status wire' inside. This module is also receives signals from the remote. I would like to find at least the 'Lock' circuit for the remote so I can keep my auto-windows-down feature (i.e. tie the alarm to that circuit and latch it to roll the windows down).
The problem with the CIM is they're expensive, and if they go bad, a dealer has to program them and re-marry/re-flash every module in the car.
Oldspark, you've been a great help with all of this! Thank you for your help! How do you feel about controlling the power to the LM339 circuit via relays? If it's a good idea, should I use a micro SPDT 12V relay to keep the heat low?
No question is stupid or not worth asking. You were once a noob, right? :)
oldspark 
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: February 11, 2014 at 7:18 PM / IP Logged  
There MUST(??) be a way of synching or latching this beast. I feel it - but ATM my head's too heavy to realise it.
Relays for the 339?
My first comment is that - except if ON when 'the power source' is on (ie, IGN on or alternator is charging) - I consider it silly to use something to turn something on when that use more power than the thing being turned on. IE - a relay consumes say 60mA to 250mA whereas the LM339 itself consumes ~2mA, maybe 5mA.
Chances are that whatever you use to energise the relay can power the 339 circuit direct, else via a MOSFET or transistor (on the +ve side, but -ve/GND side may be ok in this case).
FYI (ramble only...) - note 'the power source' issue. I use a relay to turn on my dash's 3 digit voltmeter. The voltmeter consumes 7mA.   But it's only on when IGN is on and hence the relay is a negligible addition, and irrelevant once the alternator is charging.
And the relay is required because it's a 2-wire voltmeter. Hence it measures voltage across its 2 wires and - of course! - I'm measuring battery volts - not battery volts after fuses, connectors IGN switches, etc.
Admittedly I am using a tiny DIP relay with a 1k coil (hence ~12mA or equivalent to a LED) and it also has manual activation and hold-on with a timer, but the point is that's one application where a 250mA relay to power a 7mA load is valid, and quite acceptable.
But I often see ridiculous installs where some high current drain is used in standby applications - eg, NE555 timer circuits on batteries or monitoring solar applications (the 555 itself consumes 10mA), or energised relays to turn on things when IGN is off (instead of using an SPDT NO contact), etc.
freqsounds 
Copper - Posts: 289
Copper spacespace
Joined: October 17, 2008
Location: Virginia, United States
Posted: February 11, 2014 at 7:49 PM / IP Logged  
oldspark wrote:
Relays for the 339?
My first comment is that - except if ON when 'the power source' is on (ie, IGN on or alternator is charging) - I consider it silly to use something to turn something on when that use more power than the thing being turned on. IE - a relay consumes say 60mA to 250mA whereas the LM339 itself consumes ~2mA, maybe 5mA.
I agree, and I was thinking the relay would only be on for 10 minutes tops, and using ground while armed, it would only power the relay if the car was armed.
Also, thinking about how you can 'pull' a voltage, what if I diode isolate the door triggers and use a resistor to 'pull' +12V when the lines die? This would prevent the LM339 from triggering, right?
I'm just trying to think of some options! resistor based door triggers - Page 2 -- posted image.
No question is stupid or not worth asking. You were once a noob, right? :)
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