I am looking for a circuit that would be switching a relay coil and few small leds (max 3A) with a low voltage input. Now the input is variable voltage 1.1v to 5v produced by a hall sensor pot. I want the circuit to be switched on when my input reaches 1.2 or 1.3v to switch a relay with 12vdc. Also the 1.1v to 5v values can not be affected by this additional circuit. Any help greatly appreciated .
Use a comparator to sense whether the signal is above or below your 1.25 V threshold. Use the output of the comparator to turn on a transistor, which then turns on a relay.
Driving a relay from a digital signal has been discussed many times here before, so I won't repeat it. Here is one example.
Any suggestion on it , diagram ? Im coming from auto elec. field and not too familiar with IC chips. thanks
There are plenty of examples on the web. Here is one: -
You'll need a 1.25 volt reference to feed one input of the LM339 and the other input is from your hall sensor. The voltage reference is common-place and there are many options such as this link from Mouser.
Q1 is virtually any PNP transistor. The 470 ohm and LED are optional.