Joule Smasher Led Flasher - Second Trial Results

Results

A quick update because the previous blog regarding the interim results covered many of the findings from the second trial.

 

Despite some mishaps with battery holders and boost control failures it was the a surprise when the battery that did a lot of extra work with flashing and verification lasted the longest. Note the led was hanging off the MISO line so data transfers were always flashing it. I'll be changing this in due course.

Taking the life of the best AG3 cell to be 18.6 days I divided the time axis for the first fresh AA cell I started testing by 193 (365*10.18.6),  Compare the AG3 battery with the results to date for the AA cell I get the following:

It's early days but the AA cell is putting in a good start. Nothing so far to suggest it will not achieve 10 years of life.

Boost Control

Having dispensed with boost control I went back and modified the boost control boards to be always on. I then re-ran a trial for that board. In every instance the "Always On" version lasted longer.

Watchdog Oscillator

I learned that the watchdog oscillator was running slower than expected because of the lower voltage. In fact, it never reaches 128kHz at any temperature or voltage so I'm amazed it's called a 128kHz oscillator. All my calculations and code have been adjusted for this. 

Near Final configuration:

A 3v boost convertor with better efficiency than that used in the trials.

3ms (measured) at 9.6mA (measured) of led current.

Flash every 2.3 seconds

Overall power consumption of 52uA.

Expected Life exceeds 10 years from a AA battery.

There is still a little more hardware optimisation to be done. Something I'll be pursuing as time permits.

Housing the Joule Smasher Led Flasher

It amazes me that often the enclosure for a project costs more than the rest of the project. Here is one way of keeping the costs down: plastic centrifuge tubes. Perfect for indoor use.