Detecting current in 12v system

In summary, a resistor is placed in series with the device, and the voltage is measured across it. If the voltage is higher than the 12v supply, then the device is on.
  • #1
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
 
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  • #3
A few options...
http://www.linear.com/ad/current_sense.jsp
http://www.maxim-ic.com/app-notes/index.mvp/id/746
http://focus.ti.com/analog/docs/microsite.tsp?sectionId=560&tabId=2180&micrositeId=7
 
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  • #4
Thanks for the suggestions! Excellent forum.

Regards
 

FAQ: Detecting current in 12v system

How can I detect current in a 12v system?

There are a few different methods for detecting current in a 12v system. One common way is to use a multimeter, which can measure the amount of current flowing through a circuit. Another option is to use a current sensor, which can be connected to a microcontroller or other device to measure the current. You can also use a shunt resistor, which can be placed in series with the circuit and measure the voltage drop across it to calculate the current.

Why is it important to detect current in a 12v system?

Detecting current in a 12v system is important for several reasons. It can help you troubleshoot any issues with your circuit, ensure that components are receiving the correct amount of power, and prevent potential damage to the system. It can also be useful for monitoring power usage and efficiency.

What is the difference between measuring voltage and measuring current?

Measuring voltage and measuring current are two different ways of assessing the electrical characteristics of a system. Voltage is a measure of the potential difference between two points in a circuit, while current is a measure of the flow of electric charge through a circuit. In other words, voltage tells you the force behind the flow of electricity, while current tells you the actual amount of electricity flowing.

Can current be detected without disrupting the flow of electricity?

Yes, current can be detected without disrupting the flow of electricity. This is typically done by using a non-invasive current sensor that can measure the magnetic field surrounding a wire or by using a shunt resistor that has a very low resistance and will not significantly impact the flow of current in the circuit.

Is it safe to detect current in a 12v system?

As long as proper safety precautions are taken, it is generally safe to detect current in a 12v system. It is important to use the appropriate tools and techniques, such as insulated gloves and a multimeter with the correct settings. If you are unsure about how to safely detect current, it is best to consult with a professional or do thorough research before proceeding.

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