logger power , sleep power

[bethesdakid]

logger power stays ~42,7ma at 10 sec cycle time to ~42.7ma / 60 sec cycle time to -42.7ma at 10min cycle time. hence no savings when minimizing data logging, The power down function only reduced power to ~36.8ma. which is a 14% saving... not enough when you are logging a DHT sensor/logger system with a 9V battery for 3-5 months not 40 hours not even 2 days...

Here is the question... How much different is the WDT. where does the WDT go in the loop for 10 min calls and how can it be extended to about 8-9 minutes of power down between calls?

[adafruit_support_bill]

There are some notes on WDT usage here: http://letsmakerobots.com/node/24536. But one of the bigger problems with trying to save power on the Arduino is the 7805 linear voltage regulator. With a 9v power source, you are only about 55% efficient. You might consider using 4x NiMh (4.8v) as a power source, or using a more efficient 'buck' regulator such as this one to bypass the 7805:

[pgrunwald]

How does this method compare to using this: http://code.google.com/p/narcoleptic/ ? Does one have advantages over the other?

[adafruit_support_bill]

How does this method compare

The narcoleptic library looks like a good one. But it doesn't address the fundamental inefficiency of the 7805 voltage regulator. With a 9v source, you are throwing away almost half your available power. To maximize battery life, you would want to combine your low-power sleep strategy with a more efficient voltage source.

[pgrunwald]

Thank you, do I have to use NiMH or could I use Lithium? (do I have to stay below 5V?).

Thanks,
Paul

[adafruit_support_bill]

You do want to keep it below 5v. (The absolute max rating for the Atmega is 5.5v). But you can get an Arduino to run on 3.3v, so it would probably be OK running on a single lithium cell. Not sure about the logger though. The on-board 3.3v regulator need some 'headroom' to regulate properly. The other option would be to go with 2 lithium cells and one of these: http://www.adafruit.com/products/1065

[bethesdakid]

thanks ada support. .. I did change to a 4ea 1.2V, 2450mAh battery producing 4.6V, 2450 mAh supply that reduced current of ardun/log w/ DHT 22 that resulted in a current of 20.1 mA. That will extend operating time to about 5 days. Now what can be done to get at least 3-5 months.

the next action I take will reduce CPU power. The Narcoleotic library is stated to reduce CPU power from 15 mA to 7 uA ! if that is true, it will mean that putting the unit to sleep without doing anything else, the power will go to about 5mA. The life will be approximately 500 hours or about 20 days.

What about it AdaSupport.. . Does that compute?

BTW... a trans-rec had scared the animals and some left,the darkened cage. would also like to use an IR detector to verify movement in enclosure... what simple IR sensor is available?

[adafruit_support_bill]

Although the Arduino may be sleeping, the logger and probably your DHT 22 are still powered. You might consider using something like a MOSFET to switch power to the shield/'sensor only when the processor is awake.

The PIR sensor in the store will detect animal movement: https://www.adafruit.com/products/189

[pgrunwald]

Any idea when the shields will be in? they have been on back order for a while.

[adafruit]

will be any day now!

[bethesdakid]

A test of narcoleptic was done with just the Arduino board and 4 ea 2000 (duracell) rechargable AA batteries. The nominal current was 27ma. Running the narcoleptic (MerlinTheCat) Power-down reduced the current to 19ma. Basically, the Arduino Uno R3 CPU, the Atmega328d, becomes inactive reducing the power consuption. So, the 8 ma reduction only shuts down the ATmega328d.

Other board systems are obviously still operating.

So the questions are:

A. how can the other systems on the board be reduced in power if the Arduino is to operate several times a day with only a DHT sensor and an IR detector ( several = 1 to 4 times) ? what other programs are necessary to do that?

B. This device is to be used with a logger shield. The total operating current is about 43 ma. Hence the shield takes 16ma. Can it be shut down to conserve power? What program will do that?

[adafruit_support_bill]

As suggested earlier in the thread, you might consider using a MOSFET to switch power to the shields. This would involve cutting the trace from the 5v pin that supplies power to the shield and switching it via the MOSFET. If you have space left in the prototyping area of the shield, that would be a good location for the MOSFET.

The MOSFETs we carry in the store can be switched with a 5v logic signal. The Arduino can drive the signal high when it is active and let it be pulled low when it goes to sleep.

https://www.adafruit.com/products/355

[bethesdakid]

the test without the logger shows that the AA's will run a max of 5 days... need to reduce the power to at least 5ma for 20 days, optimum is 1 ma.
what software will do this?

I have a MOSFET that will be used when I install the logger shield...

[GordieGii]

You need to modify the existing sketch to turn off the FET(s) before putting the Arduino to sleep and turn the FET(s) back on when it wakes up. Then you _might_ need to re-initialize the logger and/or your DHT 22 before you use them. It sounds like a lot of hassle, but should save a lot of power.

You also might look into using an Arduino Pro. I've heard they use less power. I don't know whether there would be any other ramifications to your project.

Gordie.

[bethesdakid]

The guru stated that 4ea AA rechargeables produce 4.6V which will reduce the current loss.
Wrong!
First set produced 5.8 V.
Second set was 4.8V

so... with 4.8V batteries,

First, run the UNO rev3 by itself. Check power.
Second, same setup, with Narcoleptic sleep. check power
Third, add Logger, check power