# empty capacitor indicator + short pulse

circuit idea: // note -> times I specify in further text are symbolic

 IDEA:
-cap gets charged to full and is not currently connected to power supply
-it starts to discharge throught paralel LED + resistor over next 2 seconds
-when cap has too low voltage or capacitance to run an LED
transistors base reads LOW from LED and using a NOT gate, CAP gets connected to the
oower supply


here is a pic:

TRICKY PART
i want the last step (battery charging the capacitor)
to be 0.2 seonds long no matter what, how could I do it?

WHAT I DO HAVE :
I have all basic elements for breadboard, timer NE555 chip, a RaspberryPI

Sidequestion:
When capacitor is empty and transistors base reads low at ONE POINT
is there any way I could make that point variable
ex. Transistor reading LOW when CAP is 1/2 charged or 3/4 ?


tyvm:))

• why do you want to do this? for wider voltage variations you cannot use transistor instead you have to use opamp comparator. – yogece Nov 4 '14 at 3:37
• I don't realy see the usecase of your circuit. What is the Idea behind it? What do you want to use it for? You may use a monoflop to charge the transistor for a fix time. – Botnic Nov 4 '14 at 10:33
• is monoflop basically Oneshot (circuit)? i want the event to happen periodicaly. IDEA: when traffic light is not operating, there is yellow blinking light. I want to make LED bright then getting slowly dimmer, but at one point I want LED to get max brightness again, then repeat cycle – Not_Important Nov 4 '14 at 20:38