How to power on my board with a specific voltage?

I have an Arduino board that I'd like to power with a supercapacitor, to run for a total of about 5 seconds at a time. I want to use a small solar panel to charge the supercapacitor until the supercap is fully charged. Then I want to power on the Arduino board. I can then power down the board with a Pololu switch.

Does anyone know if this can be done? If so, how?

I’m sure that it can be done, but…

You might want to time how long it takes the Arduino to boot up from power off to accomplishing something before determining how long power needs to be applied.

I’ve done that, and I’m comfortable that I can do what I want if I can apply power for five seconds. I know I can also turn the power off when I want, so as long as I size the supercap to be large enough, I should be fine.

There was a similar thread recently:

Check that out and post if you have more questions.

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Excellent, thanks.

Something only implicit in that thread pointed to is the fast drop down of voltage during a capacitor discharge. A cap is not a battery! So only about 1/3 of the cap's energy can be used (from 5 to - say - 3.75 V) for an common Arduino. Using V-types will improve the situation of course.

5 sec @80mA are 0.4As which needs 0.1F @ 4V, hence a cap of 0.3F will do!

Oh, I ordered two super caps today and a solar panel to play with them. The caps are rated at 10F @ 2.5V. I planned to use two in series to get 5F @ 5V. I figure these would last much longer than the five seconds I need.

My only concern now is that because I am using a Pololu switch, I need to figure out a way to make a solid state normally open switch that I can "close" to activate the Pololu switch. In other words, the circuit would typically use a push button switch which turns on the circuit when closed. But I need to do this without any physical switch, just something that determines when the capacitors are sufficiently charged and somehow "closes" without movement.

I need my board to power on about every 20 minutes, then go to sleep.