I'm trying to build a Low Voltage Disconnect circuit with ultra-low power consumption and came across this particular circuit on the net
. The circuit is shown in the attached image "LVD circuit".
My challenge is to modify it to suit my purposes, and this might be a little bit out of my league, so I definitely need some help. The modified circuit should have the following properties:
-Dimensioned for control of a 12V battery package
-More or less zero current draw when off
-Less than 250 microamperes current draw when on
When integrated in my project (a battery-driven lamp) this circuit also needs to behave as follows:
-Shut down when I turn of the main lamp switch
-Turn on (start monitoring battery voltage) when I turn on the main lamp switch and keep doing so unitl the battery voltage becomes too low or the main switch is turned off.
For the on/off functionality, I've come up with a sketch. See attached image "LVD circuit modified". In this diagram I'm assuming 5V battery voltage. I've removed switch S2 and added a by-pass capacitor to kick-start the circuit without permanently bypassing the relay. But: what happens when the main switch is turned off? How can I make the capacitor discharge quickly enough without adding another resistor that continuously steals current?
As for the 12V aspect, using a voltage regulator to feed the circuit appears problematic since all normally sized (through-hole mounted) regulators are guzzling >1 mA. This is about a thousand times more than the original circuit claims to consume, and consequently a bad solution.
That was probably 10 questions in one post, so bear with me. I'm a newbie when it comes to this type of electronics, but very eager to learn. If someone could point me in the right direction, I would really appreciate it.