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Technically speaking, the statement below is incorrect. What is there is some kind of a detonation/activation circuit. Probably a wire that heats up. This would make it very very similar to a resistor... the detonator wants to heat up, the resistor does not. The resistor has just enough wire to make up the rated resistance +- a very small tolerance. The detonator does not need to be so precise.... So the material maybe slightly different. Therefore, a subtle difference... In any case splitting hair, here.

The ECU uses the fact that there is a very small heating element with a small but measurable resistance. It sends a very small current to see, if there is no short or open circuit. It sets a light, if it sees short or open. The ECU needs to send a very small amount of voltage and current as to take the measurement but not detonate the airbag.

As I mentioned before, a detonator is not a precision resistor, since that is not what it is used for. So the ECU knows that it is looking for something around xx Ohm... An open circuit will not work, a very large kilo-ohm resistor will not work, as very small resistor will not work. What is the range acceptable to the ECU, we do not know. Safe to assume 1 to 5, maybe 10 ohm....

Resistors are rated by the amount of energy they can dissipate. Hence, 5W resistors, etc. A resistor resists the current. The energy that it resisted turns into heat. The higher the energy rating the more heat the resistor can dissipate, the bigger the actual part. Small circuit-board resistors are 1/2 or 1/4 Watt or less. Large wire-wound units are 5W or 10W +, they are just like large heating elements. :)

Using a higher Watt rated resistor is OK. It just takes up more space. (Has more inductance which is not desirable in high fidelity audio...)

The ECU is not sending a lot of current by definition, so large Watt resistor is not necessary. However, as long as the ohm rating is in the ball-park, it will work just as good.

Thinking about this more.... If one was to put in a small resistor instead of an airbag... and there was an accident.. ECU would send a lot more current to the resistor to activate the airbag (that is not there)... This will make whatever the resistor there very hot, just like the detonator, they are the same this way, after all.... may cause a small fire....

Does anyone know of what an ECU does to the airbag voltage and current for activation and for how long?

Anton


a resistor will work if you use the right one. after all thats what is there to begin with
 
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