Automotive lock function sensor

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ang4march
 
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Re: Automotive lock function sensor

Post by ang4march »

Zener,

Have you gone on vacation? Have you moved on? Do I need to start this conversation again with someone else?

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zener
 
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Re: Automotive lock function sensor

Post by zener »

Hi, Sorry I missed your previous post. It is pretty unclear to me what you have there. I would have to see a schematic showing all that to give any more specific advice. All I can say is if you want to monitor the motor resistance itself then you need to measure the current going to it and see if it is correct or very low. You also need to know when the actuation was attempted, in order to know when to monitor the current, and that could be determined by measuring the voltage to the motor, or maybe a signal from the switch. Current can be measured with a shunt, or with a hall sensor. I was going down the path of using a shunt, however you would need to know how the circuit is referenced to ground, since any device measuring the voltage across the shunt (like an Arduino) would be referenced to ground also.

So that is about as far as I can go at this point. Maybe someone else has a better idea.

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ang4march
 
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Re: Automotive lock function sensor

Post by ang4march »

Locking schematic 2.jpg
Locking schematic 2.jpg (102.37 KiB) Viewed 285 times
Locking schematic 1.jpg
Locking schematic 1.jpg (103.78 KiB) Viewed 285 times
Here are some schematics...do they help?

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zener
 
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Re: Automotive lock function sensor

Post by zener »

Those schematics look decent. I can give you some fairly good guidance toward what I am thinking, but I am not a custom engineering and debugging service. You can find those on the jobs board. There will be details to work out and troubleshooting to do. This is a medium complexity project so you will have a lot of work to do. I will throw up a concept drawing and then maybe others can provide their opinions.

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mobiusrx7
 
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Re: Automotive lock function sensor

Post by mobiusrx7 »

I think you may be overcomplicating this a bit. Not to be a negative nelly, but this seems like creating a solution to a problem that doesnt really exist?

Why not just replace the lock motors? Surely the new motors will outlive the rest of the car, or at least last long enough for the children to reach an age where they know better than to unbuckle/jump out of a moving vehicle.

Also, there can be many reasons as to why the lock mechanism isnt locking. Measuring the motor as you describe only really takes into account one, and likely only during the actual movement of the lock mechanism. As was already mentioned, if you simply want to know that the door has/or has not locked, you would need to measure whether or not the mechanism has moved it's full travel. Nothing complicated, you just need a switch, a LED, a resistor, and some wire.....

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zener
 
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Re: Automotive lock function sensor

Post by zener »

Well, I already said that....

Anyway, I was about to unveil my masterpiece, but I noticed a fundamental problem with this which is, all 3 door locks (both rears and the passenger front) are powered by a single pair of wires from the BCM. Only the driver lock gets its own circuit. So, even IF we could determine that one of the 3 was bad, by noticing a small difference in current, we would not know which one. Let me know if that is OK.

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zener
 
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Re: Automotive lock function sensor

Post by zener »

OK, so here is what I have. First "STEP 1" the circuitry to produce some voltages that could be deciphered. The V in the circle represents a volt meter. You would put a volt meter there to see what voltages you get under the different circumstances. I have noted my predicted values.
STEP 1.png
STEP 1.png (175.5 KiB) Viewed 260 times
Then STEP 2, if step 1 went OK then you can use an Arduino to read the voltages. I did not show any display or lights but you could add that.
STEP 2.png
STEP 2.png (233.45 KiB) Viewed 260 times
*** Edit, I just noticed my first error, I forgot to put clamping diodes on the second circuit. It needs a couple of diodes just like the first one, to protect the analog input when the door unlocks and that line goes to 12V ***

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ang4march
 
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Re: Automotive lock function sensor

Post by ang4march »

Thanks very much Zener. This is helpful.

We have already inserted a rheostat inline with the motor to define the range of voltages under which it will function and I found my long-lost clamp-on ammeter, so I think I'm ready for action.

I will try to digest this and begin experimenting. Is there anything I need to know about the Adafruit products and literature beyond just ordering an Arduino and digging in?

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zener
 
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Re: Automotive lock function sensor

Post by zener »

ang4march wrote:We have already inserted a rheostat inline with the motor to define the range of voltages under which it will function
I am not sure what you will do with that particular information
ang4march wrote:and I found my long-lost clamp-on ammeter, so I think I'm ready for action.
Most clamp on meters cannot measure DC current. Some can but they are the exception not the rule. Just make sure it can if you are trying to do that.

You can order an Arduino now if you want but I would verify you can get useful voltages to measure before you hook it up to anything.

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ang4march
 
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Re: Automotive lock function sensor

Post by ang4march »

OK, thanks again.

I made a discovery today in a junkyard. There is version of this same latch with a lock position sensor built into it. It is a simple on/off switch that senses the position of the locking linkage inside the latch. It may be easiest to adapt the external linkages from the '03 Impala latch to the latch mechanism and electronics of this other version from a '97 S-10 Blazer. I'm going to check out the packaging and clearances, but I think it is feasible.

This may simplify everything and address the critical comments from mobiusrx7. It should get around having to look at durability, tolerances and other fiddly mechanical issues.

Locked
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