I am attempting to build a circuit which runs an Atmega 328P from the secondary winding of a current transformer (CT). I can charge a 22000uF capacitor to around 8v in approximately 20 seconds, provided I have no load connected. The micro-controller is programmed to drop immediately into sleep mode, during which the input from the CT is sufficient to keep it running. I have a 5v 100ma regulator to take the 8v and drop it to 5v for the chip. However, the problem is that on startup significantly more current is used, so the voltage will rise to 1v or 1.5v, at which point the chip starts sinking the tiny bit of current available, and prevents further charging.
I have tried using an LM339 comparator with one input tied to 1.8v by a red led and resistor, and the other being whatever is in the cap, but the LM339, resistor, and LED together again use too much power before they actually start working, and in the meantime leak voltage through to the micro-controller anyway.
I have also tried using a Schmidt trigger inverter which was better than the comparator, but again, it leaks voltage through as well as using some power itself, and still will not let the capacitor charge.
In addition to this I have tried a transistor and P mosfet with a good chunk feedback to make it 'snap' open and closed as per https://jeelabs.org/2015/05/13/micro-power-snitch-success/ but this does not seem to work either. Some probing with my meter suggests that the two LEDs are burning up the power which should be charging the capacitor.
What I need is something like a voltage regulator which stays firmly closed until a set voltage is reached. There must be some ic or circuit around for doing it (maybe solar charging would be similar), but I can't seem to find anything. After three days of trying different options I'm beginning to wonder if this is the reason why so many devices have RTC modules with a coin cell to fire a wakeup call. Am I going to have to default to this, or is there a method completely without batteries?
I have tried using an LM339 comparator with one input tied to 1.8v by a red led and resistor, and the other being whatever is in the cap, but the LM339, resistor, and LED together again use too much power before they actually start working, and in the meantime leak voltage through to the micro-controller anyway.
I have also tried using a Schmidt trigger inverter which was better than the comparator, but again, it leaks voltage through as well as using some power itself, and still will not let the capacitor charge.
In addition to this I have tried a transistor and P mosfet with a good chunk feedback to make it 'snap' open and closed as per https://jeelabs.org/2015/05/13/micro-power-snitch-success/ but this does not seem to work either. Some probing with my meter suggests that the two LEDs are burning up the power which should be charging the capacitor.
What I need is something like a voltage regulator which stays firmly closed until a set voltage is reached. There must be some ic or circuit around for doing it (maybe solar charging would be similar), but I can't seem to find anything. After three days of trying different options I'm beginning to wonder if this is the reason why so many devices have RTC modules with a coin cell to fire a wakeup call. Am I going to have to default to this, or is there a method completely without batteries?