I have a plan, I have been struggling with. Any help would be tremendous.

My plan is to build a circuit that would sense a voltage in a delicate sensor feed wire. Upon seeing a specific voltage of lets say 1.5 volts it would send a 12 volt ground (or power) signal to another load with a current draw of about 1 amp. The delicate sensor wire I would be reading produces a votage signal of between .5 and 4.5 volts DC. My circuit needs to not interfere (have high impedance) with the signal voltage at all, and I also need to be able to adjust the voltage break point at which the circuit would energize the load. I have been playing with some zener diodes, and-gates, resistors, and transistors but all my attempts have failed. A high impedance voltage alarm relay is the best way to describe this project. Any ideas??? :?:

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Andrew in Georgia

 

An opamp with FET inputs like a TL071 or TL081 would be perfect.

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Uncle $crooge