BS2 power consumption

Britannicus · 2011-03-03 03:41

Hi there.

I'm contemplating a project for my BOE to water my plants on holiday. I'm intending running the BOE on a standard 9v battery - leaving the stamp to tick away time over the days. Then on a daily basis to switch a small pump to water the plants daily.

The pump has it's own power supply 12v battery, so I'm only using power to switch it for 2 mins a day (5V 10Ma draw). My question is, how long will a BS2 stamp run on a duracell 9 volt battery before flattening it? - I've no measure, as in the past I've always run servos etc off the battery and so it's not lasted very long.

If I simply use it as a timer - how long before the battery dies from just the power drawn by the stamp and the LED in the BOE ? is there any way to prolongue battery life? I'd run it from a wall socket, but there isn't one available .

Cheers Chaps

Mike G · 2011-03-03 04:42

According to the published BS2 specs

@5V 3 mA Run; 50uA Sleep

An alkaline battery is 400 to 600 mAh. So 600/3 is 200 hours.

is there any way to prolongue battery life

Solar power, sleep at night or the day, get a battery with more capacity, use a real time clock, run off the pump power.

Tracy Allen · 2011-03-03 09:37

I second Mike's suggestions.
The SLEEP command is pretty accurate at long time intervals, certainly adequate for a holiday, and what does the plant care about that accuracy anyway?

For two minutes a day it would be,

DO
     HIGH watering
   PAUSE 120   ' 2 minutes,  could even use SLEEP 120 here if the pump can tolerate 2 second glitches
     LOW watering
     SLEEP 43200   ' 12 hours
     SLEEP 43080   ' 12 hours minus 2 minutes
LOOP

At 50 µA for 86280 seconds and 10 mA for 120 seconds, the average power drain is approx.:
(0.05 * 86280 + 10 * 120)/86400
= 64 µA

And that 500mAh batttery should last for 500 / 0.64 = 7812 hours = 325 days. Better come home from holiday now!

Be sure to put unused Stamp pins in definite states so that they don't float--bad for power drain.

Britannicus · 2011-03-04 11:37

This is great - given a bit of thought - I'm not now going to use a pump - just have a reservoir with gravity feed. then use the stamp to control the flow once a day for a few seconds - easy peasy !

Thanks for pointing me at the Sleep instruction - must've missed that one !

Spiral_72 · 2011-03-04 13:55

I'd base that decision on how big your reservoir is. Gravity, water and in your house is a disaster waiting. Don't ask me how I know this

BS2 power consumption

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