I am working a constant current electronic load .. I was wondering if I could take one of the opamp and take the input and put it across a power resistor ( 1Ω 50 watt) and use it to measure the current in volts but to trigger high at say 3amp to a relay to shut everything down ?????





Thanks
Jason SR

 

I am working a constant current electronic load .. I was wondering if I could take one of the opamp and take the input and put it across a power resistor ( 1Ω 50 watt) and use it to measure the current in volts but to trigger high at say 3amp to a relay to shut everything down ?????

If the voltage is DC, then yes. You could use a comparator or op amp used as a comparator with a reference voltage of 3V to indicate the shut-down point.

 

If the voltage is DC, then yes. You could use a comparator or op amp used as a comparator with a reference voltage of 3V to indicate the shut-down point.

Here a schematic

 

Here a schematic

Comparator comparing nothing.
What's your Voltage for load?
What's your voltage for comparator?
I was used an op amp to designed a similar function, but it's not likes that way.

 

Here a schematic

This comparator will only tell you if the current in the sense resistor is positive or negative.

You want a differential amplifier followed by a comparator (and, yes, they can be combined into one opamp circuit, but it is generally better to break up your functions into well defined blocks).

 

With an op-amp/comparator circuit you can use an even lower value, and therefore lower wattage sense resistor. Also, less voltage drop occurs for a given current through the sense resistor.