Low-Power Battery Backup Reference Design

newplumber

Senior Member
what variety do you prefer for flavor or texture?

sorry lance I'm a little/very late from ur question
I am on a diet I've been 165 lbs 20 years ago when I was 20
and now I am 166lbs so I have been forcing my self to eat more
healthy foods like donuts,twinkes, candy and sugar galore sodas
trying to get to 170
and i going to celebrate when the blinker dies
I think you have a world record here so far ...which for reals is good info
 

lbenson

Senior Member
world record here so far
Never imagined it might be a topic for consideration 9+ years later. It is good to know that it is possible to run a low-drain picaxe on batteries for a long time.

Re "record", haven't heard from papaof2 for a while, so don't know if his water sensor is still running (and on same batteries), but his project predates mine:
http://www.picaxeforum.co.uk/showthread.php?7685-Rising-water-alarm-sump-pump-controller&highlight=water

Unfortunately, the site referred to for details is dead.
 

lbenson

Senior Member
Yesterday was the 10-year anniversary of the first posting in this thread, and the green LED is still blinking away, approximately every 7 seconds, on the original 3 AA batteries. The battery level is now at 3.56, down from 3.67V last year. That's approximately 45 million blinks.

I had no idea that the PICAXE could run for so long on what manuka might say is "a whiff of the odd electron".

Now back in its box for another year.
 

techElder

Well-known member
Lance, I put a rock in a box way back near the time you started this experiment. Its still in the box and still a rock. :D

PS. Please, just having some fun! :D
 

lbenson

Senior Member
... still in the box and still a rock ...
The question is, by how much has the useable energy in the rock been depleted? At a rough guess, I would suppose that your rock will be better for a much longer time at whatever a rock is good for than my batteries will be for what batteries are good for.
 

newplumber

Senior Member
Lance thats awesome ....calculating the math here ...I suppose it will last for another 2 to 12 years if I round up correctly :)
but its still cool to know its still going strong
 

lbenson

Senior Member
But does the LED still flash when the box is closed or does it only flash when the lid is off? :p
The box is just for storage. But this may be the same as the question, "If a tree falls in the forest with no one to hear it, does it make a sound".

Let's see--I could install a flash detector, or would just monitoring the LED supply line for plus voltage suffice?

Nah, I think I'll just suppose that what happens when I'm making an observation is the same as what happens when I'm not (Schrödinger and his cat notwithstanding).
 

lbenson

Senior Member
Time for the 11th-year annual update. No sign of life from the green LED. I hot-swapped in a high-brightness red LED, and it's blinking away--more visible than the green one was. But the original 3 AA batteries are down to 1.87 volts, so I think another year is unlikely. All good things must end.
 

hippy

Technical Support
Staff member
Eleven years is a good run. More than anyone would probably have predicted. I have had batteries die on the shelf in far less time than that.

You are getting down to that level where the PICAXE might not be able operate, so it looks like its time is coming. Would love to see it achieve another anniversary.

One thing you could do is short out the LED resistor if there is one, drive the LED directly, if this LED gets too dim. Or replace LED+R with a piezo which should at least give a 'click' when it flashes.
 

RNovember

Well-known member
Hey, when it finally bites the dust, you should try it again with charged batteries.

Or you could have a contest with any one interested to see who can keep one going for the longest.
 

Buzby

Senior Member
Did you keep a record of the voltage at each of the annual inspections ?

It seems that in the last year the voltage has dropped considerably more that it has in the previous years.

Is it possible that at a low voltage the PICAXE glitched, and kept the LED on for minutes, not milliseconds ?.

Is there a dry joint or an oxidised terminal somewhere ?.

Still, its a great acheivement. ( Not so much about the longevity of the kit, but the fact that you can still find it after 11 years. )

Cheers,

Buzby
 

hippy

Technical Support
Staff member
Taking the voltages given in this thread and filling in the gaps ...
Code:
               1         2         3         4       Volts
     0123456789-123456789-123456789-123456789-12345
2007 |                                           +
2008 |                                          #    4.26
2009 |                                          +
2010 |                                         +
2011 |                                        +
2012 |                                       #       4.01
2013 |                                       #       3.98
2014 |                                      #        3.89
2015 |                                     +
2016 |                                    #          3.67
2017 |                                   #           3.56
2018 |                  #                            1.87
It does seem that it 'fell over the cliff' in the last year.
 

Buzby

Senior Member
Is it possible that at a low voltage the PICAXE glitched, and kept the LED on for minutes, not milliseconds ?.
I've just thought of another possible issue when at low volts.

Are the output MOSFETs ( inside the chip ) switching properly ?.

If they are only getting half-biased, they might be both on at once. This would make the chip use hundreds of electrons all the time, insteads of just a whiff every ten seconds.
 

lbenson

Senior Member
Did you keep a record of the voltage at each of the annual inspections ?
The only record is in this thread.

Is it possible that at a low voltage the PICAXE glitched, and kept the LED on for minutes, not milliseconds ?.
Quite possible, but I have no way of knowing.

Is there a dry joint or an oxidised terminal somewhere ?.
Maybe. It's on a breadboard.

Still, its a great acheivement. ( Not so much about the longevity of the kit, but the fact that you can still find it after 11 years. )
"find it after 11 years" Yes, I hear that. I can find it because after it surprised my by lasting for a few years, I put it in a box which is in my sight from my desk, but opened only once a year.

I was surprised at the voltage dropoff compared to past years, but just figured there was a steep tail at the approach of end-of-life for the batteries.
 

lbenson

Senior Member
Which, after all this, is the only item being tested; sort of.
It didn't start off that way--it was meant to be an example of how to run an 08M off of a battery with low current draw. After it kept going and going for several years, it became a challenge to see how long it would last--hence the preservation of the project in a box.
 
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