Quote:
Originally Posted by onelove
Does the car need to see variable resistance ? I would think the easiest way would be to fool the car into thinking you always had a passenger or never had a passenger (if it mean the seat belt chime always was indicated).
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Correct. The easiest thing to do would be to fool the car into thinking you always/never have a passenger via a single resistor. However, I want the ability to turn the airbags on or off with the flip of a switch. I don't plan on carrying a car seat but occasionally I do have small cargo in the seat and want the airbag off. ~50% of the time I carry a passenger, and I'll leave the airbag on when they're in the car. But there are times when the airbag would be extraneous or dangerous, so I want the ability to turn it off.
While it sounds complicated, it's really not that hard to create the circuit. Find the resistance with and without a passenger, and make a circuit with those two resistances and a switch. After you do it once it's a matter of duplication. My results will be posted here, and I may consider soldering some up to sell to those that don't want to deal with it... though I'm hesitant because this is a safety feature and don't want to risk being sued because someone forgot to set the airbag accordingly.
I did some more testing yesterday to figure out the voltage change across the sensor ("input voltage") and had some unexpected, though not necessarily bad results. I couldn't get a constant DC voltage from the seat's plug (sensor unplugged). I'm guessing the seat doesn't use a constant 5/9/12V. Instead it's more of a pulse. I had a hard time getting my voltmeter to the plug to take the measurements; the harness had to be plugged in so the seat would have power. It's somewhat difficult to get a multimeter to the back of the seat while it's plugged in. When I finally got a reading, it was jumping all over the place. The range was about .3-.7V with about a 5Hz update rate (guess).
A pulsed input voltage won't affect the operation of the airbag and switch. It does eliminate the ability for me to incorporate a LED, because a LED requires a constant DC voltage. So, it looks like I'll have to have a boring rocker-type switch with no cool light on it.