Super Capacitor in solar power supply - a few queries
April 8, 2010
I intend to build a remote 'weather station'
The station will:
- Be completley independant of any external power, ie, it will produce its own power via solar cell(s)
- Measure temperature only
- Transmit its finding over an RF link to an indoors reciever
Instead of using a rechargeable battery supply with charger circuit, i have decided to use a 35F, 2.7V super capacitor to smooth and store power.
The power scheme will run along these lines:
Panel Array* ===> Diode ===> Super Cap ===> Voltage boost to 5V via pololu voltage boost ===> Remainder of circuit
*The output voltage will preferably be ~1.5V, as my super cap is rated at 2.7V and i hear a general rule of thumb is to keep the impressed voltage at around half the rating for long capacitor life.
I have several questions concerning this setup:
How can I ensure that the total power output by the panel(s) and capacitor will not cause the voltage boost (and subsequently my logic circuit) to "hiccup."That is
"The power supply will shutdown, then restart itself. This will repeat until either the overload (?) goes away, or a component in the power supply fails from trying."
This hiccup theoretically occurs at the voltage boosts minium input, which is rated 0.8V.
I have tested this with a panel, the volt boost, a picaxe 08M, and a simple program to flash an LED on for a second, off for a second, repeat. I didn't use a large cap as it hasn't arrived in the mail yet, but that shouldn't matter as this would mimic a real life situation cap or no cap anyway.(?) My results were that when the power produced by the panel was on the border of the volt boost's specs, the LED flashed several times a second, implying that the volt boost was rippling on and off many times a second. I expect this kind of situation to occur during twilight hours when the panels + cap may not be able to support power production, or at night when the panel has ceased functioning, but the cap's voltage has decayed to the edge of the voltage boosts limitations.
After all that background, i can finally ask: Is this 'hiccuping' actually damaging to the power supply, picaxe or RF transmitter?
If so, how can I prevent it?
Wherever i have made a bracketed question mark in my post, i am hoping someone will come along and b*tch slap me with some knowledge.