Fighting with computers

Computers are not always friendly.

Saturday, November 22, 2008

Some power benchmarks

After some time willing to do this I've found a moment to do some measurements. Firstly, I've removed Arduino Mini Pro power led resistor to see how much current was needed for the device in power-down mode: It's just 155uA@3V3, even lower if you go down to just 3Volts. The Mini needed 5mA for normal operation (with no output loaded).

The other component I was interested on testing together was Digi's XBee module. While XBee needs 50mA on operation, using SM=1 (Hibernate mode) the power goes down to 1.6uA when sleep mode is forced (by raising pin 9 to high).

That all means that a basic wireless sensor node based on this components will use at least 55mA during ON periods and 0.16mA while SLEEP. That translates into about 4 hours of continuous operation from a 220mAh 3V button cell.

However, if node is powered up only 3 seconds every 5 minutes, then the same battery should last around 13 days. This seems to start looking ok for my sensor network project.

9 Comments:

  • At 1:51 pm, Anonymous Marco Zennaro said…

    Thanks, very interesting! I linked this entry to my blog, wsnblog.com.

    Best,
    Marco

     
  • At 4:36 pm, Blogger Miguel Sánchez said…

    I'm glad to be useful. Thanks for linking it.

    Cheers,

    Miguel

     
  • At 1:11 pm, Blogger Gustavo said…

    Hola Miguel, gracias por tu aporte es un buen punto de comparación para comenzar otro proyectos.

     
  • At 1:40 pm, Blogger Miguel Sánchez said…

    De nada, Gustavo.

     
  • At 7:23 pm, Anonymous Andro Bačan said…

    Im not quite convinced that button cell battery can give 50 mA for XBee module. Try test with battery instead of power supply, and record (with scope) voltage of battery when it's heavy loaded (50 mA is much for coin battery).
    For project I designed my own Sensor node (yes, it's silly, I know), and it runs on LiSO2 battery (3.6 V, 2200 mAh) with 4 uA sleep current and 30 mA active current. With 1 wake-up in 15 minutes (nodes are time synchronized) it can run for 10 years.

     
  • At 7:39 pm, Blogger Miguel Sánchez said…

    Hi Andro,

    Neither do I. But I guess that's why capacitors are for :-)

    Could you please provide a link to your work? (it's definitely not silly).

    I still need to find the time to put it all together and do some real test. As far as I know, 400uA is the "recommended" discharge currentfor CR2032 button cells. I'm afraid too that 100 times that may be too much.

     
  • At 10:17 am, Anonymous Andro Bačan said…

    Unfortunately, there is no web page of out Sensor node (I focused mainly on hw and node sw development). It was project on university where I worked with colaboration with industrial partner. You can find some material on web page www.maslinet and on http://aig.zesoi.fer.hr/archive.html.

    Regarding capacitor use, be aware that larger capacitor (and, for these use you will probably need > 1mF capacitor) have significant (few uA, for this use) leakage current.

     
  • At 2:21 pm, Blogger johannes said…

    First of thanks for sharing
    I'm making a automated watering system with soil humidity sensor, relay board, 2 18650 2500mAh Li-ion cells and 5V mini pro (putting my uno on the shelf since there is only a small difference between delay and pwr_down in power consumtion).
    I was wondering if you passed through vcc or raw while measuring and if there is a big difference since I will be getting 5.2-8.4V from the cells.

     
  • At 4:03 pm, Blogger Miguel Sánchez said…

    Dear Johannes,

    The problem with battery voltage in your case is that it is too high to safely power Arduino. Because of this a voltage regulator is needed, but unfortunately, the regulator idle current is likely going to exceed by a fair amount the power needed by Arduino to be sleeping.

    I'd try to find a way where you could power the board directly from a battery without the need of a voltage regulator in between.

     

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