Thanks. Think i will give it a pass.
Please give some opinions for below.
I will then design the circuit UPS for may cooler fan using 12v 500ma.
Will be using a external battery 12v cell "D" size, that will be 8 cells as a backup battery.
Compoents will be some transistors, replays, Zdiodes, resistor, inverter, buzzer.
Condition 1: 12v 500ma supply on normal usage for my x3 cpu fans currently.
Input 12v -> 5v=0, output buzzer/External Batt will be 0.
Condition 2: 12v 500ma supply fails..
Input becomes 0v, turning on transistor that enable relay, giving output buzzer/External Batt that will be = 1.
Buzzer will sound and backup batt will in control.