12 volt low voltage circuit.

Greetings all, I have a problem and am trying to find a solution for it.

I need a circuit to detect a low voltage condition on a 12v lead acid battery, and have that

condiditon true over a couple of minutes, and if true over the entire timeframe, send a negative

pulse out.  The after iginition goes open, to reset the circuit. 

Any thoughts? 

Skwearl

To detect a low battery condition you will need to select a reference voltage well below the battery output (like 5vdc).  You will then build the entire circuit at that voltage level.  You can then connect the voltage out of the battery to a voltage divider circuit (two resistors) and send that voltage in to an op amp.  The other input of the op amp will be hooked to a poteniometer. 

With this basic setup the op amp will output a signal based on the relationship of the two inputs.  If the "+" input is higher then the (-) input the op amp will output the power supply voltage on the output pin. 

You can use the op amp output to drive a time delay circuit.