I was googling groups and I came across this post from 1998. It also talked about the Forever Flasher, AKA Infini-Flasher that we talked about here a week or so ago.
He claimed that the Infini-Flasher was efficient and the only circuit that would run for 24 hours off .3 farad.
I built the circuit at the following URL and talked about it in the SED, etc. newsgroups. It says runs 6 months off a 150 mAh battery.
The first one I built used about 100 mixroamps average at 3VDC and would run for 90 or so seconds off a 6800 uF cap. I built another one, and changed some parts values, and lowered the 4700 ohm resistor to 2200, which gave it a shorter pulse width, and that reduced the average current. Now it draws an average of 44 microamps and runs for over 5 minutes off the 6800 uF cap. It's getting really boring timing this with a stopwatch.
I figured that it would take 288 of the 6800 uF caps in parallel to run this circuit for 24 hours, or a total of about 2 farads. That's about 6 times as much capacitance as the Infini-Flasher. Which seems to indicate that the Infini-Flasher is drawing only 7 or 8 microamps.
I reduced the average current substantially by changing some values, so I believe it's possible to further reduce the average current. I'm going to build another of the same circuit, but I'll use a higher value resistor for the 47 ohm LED current limiting resistor. Also, slowing the flash rate down to less than once a second will also reduce the average current.
Here's a part of the original post.
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This is called the "Forever Flasher" because, given an adequite supply of sunlight once a day it will flash forever (*even* during night-time and low light conditions).
As you said it would be pretty trivial to make an LED flasher that ran on solar cells. This one is special because it will run for about 24 hours or so in complete darkness with only .3F worth of caps. I did indeed try an LM3909 for this and it only lasted about 20 minutes on the same caps!
This is the only circuit idea I know of that will run for about
24 hours in complete darkness flashing an LED off of .3F worth of caps. Can someone come up with another circuit that's more effecient? "The sci.electronics.design LED Flasher Competition!" :-)------------------