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HeyThevenin
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I'm looking to detect when a device in a 12 volt systems is on, so that I can do something with that information -- like feeding it into an and gate. The device has it's own on/off switch inside it, so I can't simply detect at the regular on/off switch.
I was thinking about putting a small resistor in series with the device and then detecting the voltage across it. (Maybe there's a way to use an op amp to detect voltage this way, I'm not sure. My memory of op amps is a bit hazy.)
I was also thinking that I could measure the voltage across the device's power leads and compare it with the 12v supply. Maybe I could use a simple gate and some pull down resistors that would read the voltage drop as a zero instead of a one.
The device would be drawing 1-3 amps typically. It could be a light or anything else. The power supply would be either a car battery or a car battery on a charger. That would make the latter method a lot tougher, I'd think. There wouldn't be a lot of internal resistance in the power source.
Is there an elegant way of detecting whether something is on?
Regards
I was thinking about putting a small resistor in series with the device and then detecting the voltage across it. (Maybe there's a way to use an op amp to detect voltage this way, I'm not sure. My memory of op amps is a bit hazy.)
I was also thinking that I could measure the voltage across the device's power leads and compare it with the 12v supply. Maybe I could use a simple gate and some pull down resistors that would read the voltage drop as a zero instead of a one.
The device would be drawing 1-3 amps typically. It could be a light or anything else. The power supply would be either a car battery or a car battery on a charger. That would make the latter method a lot tougher, I'd think. There wouldn't be a lot of internal resistance in the power source.
Is there an elegant way of detecting whether something is on?
Regards
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