I have a couple of portable electronic devices that don’t loose their memory when I replace the batteries. I thought it would be nice to know how to do that, should I ever want to.
I picked up two 0.47F 5.5V capacitors from All Electronics for $1.65 each.
I finally got around to figuring out how to use them and built an LED circuit and an ATTiny 85 circuit both of which are powered by the super capacitors.
In my research I found it is really important not to exceed the capacitor’s rated voltage which is typically pretty low. There are plenty of videos on youtube of people exceeding the voltage and blowing them up.
The other thing is to be very careful about polarity. They can be easily damaged if connected up backwards.
Here is my basic circuit:
First, I connected 1 supercap and the LED/resistor into the circuit. It took approximately 1 min 14 secs to charge the cap to 4.5v (this is charging the cap and driving the load at the same time).
This circuit ran for about 15 minutes. At that time it was at 2.3V and the LED was very dim.
I then removed the stand along LED connected the ATTiny85. It is simply running the standard blink sketch. This ran for 13 minutes at which point the cap was at 2.2 volts. The LED was very dim but blinking regularly. After another 2 minutes the LED was barely visible but blinking regularly and the voltage was 2.2V.
I then connected the 2nd super capacitor in parallel which would give me .94F. Charged them both up in about 2 minutes.
With both capacitors, the ATTiny ran for 25 minutes.