Looking for current sensing IC

[DWE&C]

I'm looking for an IC or other small inexpensive device that will detect a 12V DC current flow of perhaps as much a 2 amps. I'm just formulating ideas and have not gotten to the point of actually calculating or measuring the current. Device doesn't need to measure the current, just needs to detect current.
All help appreciated.

 

[justDIY]

what do you mean detect?

if it's 12v DC, just hang NPN transistor from it, referenced to ground (if you use a bjt be sure to use a generous base resistor) - when current is present, the transistor will turn on, no current, transistor off

alternately you could hang an optoisolater from the 12vdc (again, resistor) - current, opto output low, no current, opto output high (assuming a typical inverted opto)

I don't think DC can be sensed from induction, so you'll have to put a shunt in series with the load to actually measure the current.

I2R tells us 2 amps will generate 400mW across a 100mOhm shunt, dropping 200mV - hook that into an op-amp and boost the voltage a bit and you've got a simple ammeter

 

[Sceadwian]

Sensing the voltage drop across the load itself might be an option without a shunt. You need to more throughly qualify at exactly what point (how many Amps) you'll consider the load to be 'on' If the device has an idle current of 200ma's and you don't consider that on it needs to be taken into acount when measuring the circuit. If you can describe a couple impedance states (such as idle 200ma's of current startup 500ma's of current running 2amps) and what the power supply impedance is then it's just a matter of calculating the right voltage divider for a comparitor setup across the load.

 

[on1aag]

Hi DWE&C,

Take a look at these application notes:

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https://www.electro-tech-online.com/custompdfs/2007/06/AN3883.pdf

https://www.electro-tech-online.com/custompdfs/2007/06/AN3669.pdf

on1aag.