Smartmeter pulse counter (3)

The smartmeter pulse counter will be the first standalone sensor I will deploy so power economy is a requirement.

I will have to power an Arduino Pro Mini and an Xbee radio. I plan to power the Xbee from the 3V3 regulated output. The Arduino VCC output can provide as much as 200mA which is far enough to power the Xbee. The built-in regulator requires at least 3.35V and up to 12V so 3 AA cells will provide enough potential to drive the whole setup. But for how long?

The Arduino will wake briefly to count every pulse and the radio has been configured to wake once every minute for 200ms and ask the uC to report the count number for since the last report. The figures for the number of pulses are based on an average consumption of 300W, that is one pulse every 3 seconds or 1200 per hour.

Once I had breadboarded the sensor I started to take some measurements in different operational statuses. You can check my results in the following table:

Arduino XBee mA ms/event events/h ms/h mA (avg)
normal transmiting ~54 200 60 12000 0.180
normal sleep 7.940 1 1200 1200 0.003
sleep sleep 0.290 - - 3586800 0.289
0.472

So 0.472 mA is the average power consumption of the sensor. The AA cells I will be using are rated 2000mAh so the sensor should be able to run for 4237 hours or about 177 days. Not bad. Off course there is room for improvement, like 290uA when doing nothing is really too much but I prefer to give it a try now before over optimizing. After all these are theoretical values and I want to know if the will match the reality.

I plan to test different approaches to power the next sensors: coin cells, LiPo cells, solar panels, rechargable NiMH batteries,…

CC BY-SA 4.0 Smartmeter pulse counter (3) by Tinkerman is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

2 thoughts on “Smartmeter pulse counter (3)

  1. Bryan Mayland

    You’re right, 290uA is pretty high for an ATmega328P + 3.3V regulator. The regulator on the Pro Mini isn’t exactly designed for low quiescent current though, so it would be better to build your own board with a more efficient regulator. For reference, the atmega in sleep mode with the watchdog timer but without the brownout detector pulls under 10uA, which can nearly double your runtime on the same batteries.

    Reply
    1. xose Post author

      Yes, building my own board would have been a better solution from the power efficiency point of view, and cheaper! The Arduino Pro Mini has the advantage of being easier to get something going on and still it’s pretty small. I have to post some pictures of the sensor. It has been running for two weeks now and there are some issues I have to address but the batteries are still over 4466mV which is the saturation point for the analog pin that’s monitoring the battery voltage (1100mV for the Arduino internal analog reference times 4.06, where 4.06 is the experimental value for the voltage divider I’m using).

      Reply

Leave a Reply (all comments are moderated, be patient)