Happy Days

Solar Production 1Who said that starting with solar panels during the winter ain’t fun? Wrong, it’s the best time of the year! 🙂
Soon after our solar panels were installed it became a habit to take a peek each day at what the panels had produced. And not being used to large production numbers, you can’t be anything else than happy with what you see; even if the production is just a few kWh.

But then, somewhere in January, you’ll start to notice that the production gradually becomes higher and higher – wow! The sun still has its bad days of course, but the production on sunny days just keeps on getting higher and higher.

So every day there’s the possibility of a new record in terms of energy production and it’s soo nice to witness that – it’s addictive. Nowadays, when I get up in the morning, I take a look outside to see whether it will be a sunny day or not; while at work I keep an eye on the cloudiness and monitor the solar production to see if another record is in the making. So, if spring itself wouldn’t cheer me up (I hate winters), our solar panels would – so right now, every day is a happy day.

If you’re considering solar panels: start in the 2nd half of winter and watch the energy production increase each week; I’m sure you’ll have the best spring you’ve ever had! 😉

Solar2

ESP8266: Good enough for a battery powered sensor?

ESP8266_power_measurements_ battery_lifeDuring the last 2 weeks I’ve collected a lot of ESP-8266 power usage charts as shown here. Enough to conclude that a ESP8266 can be used to build battery powered sensors (e.g. a temperature sensor) but how happy you’ll be after some time highly depends on the report interval. A report interval of 4 samples per hour will lead to a battery life of roughly 1 year. Increasing the report interval to 60 times an hour (once per minute) will lead to a much shorter battery life: less than 3 weeks.

The biggest problem lies in Wifi. It takes my ESP-12 about 1 … 3,5 seconds to get a Wifi connection after waking up from deep sleep. And this is by far the largest contributor to the total time needed to get a sensor value out the door. I tried several things to see if I could shorten the time needed to get a Wifi connection but had no luck; a dedicated AP for a single ESP-12, moving the AP within 2 m. range of the ESP, changing channels – nothing. Maybe turning off (WPA) security may help, but I don’t consider that as a real option. Maybe a static IP address may help (instead of using DHCP) but that’s not a real option either. Increasing the report interval of the sensor is the only thing I can think of right now to get a good battery life (of 1 year or more).

So that’s it, ESP8266 is a no-go? No way! The ESP8266 can still be very helpful in a lot of ways, I’ve had a lot of fun while exploring the ESP8266 and will definitely use them whenever I need always-on Wifi for so,me future project. And I made a nice ‘poor mans digital scope’ during all the fun as well. But it won’t work well when you want to use a relatively short report interval

Is there an alternative for the ESP8266? Lots of ’em, mine is called Zigbee. I’ve been using Zigbee modules since 2010 or so and built my own Zigbee sensors based on a JeeNode + XBee series 2 modules. For motion, temperature, barometric pressure, light intensity (lux). Batteries last about a year, that’s OK. If I would let a ESP8266 do exactly the same thing (with the same reporting interval, sensor type) as a combination of JeeNode & XBee, the batteries would probably last about 8 weeks. Wooaahhh…

I have some unused 3.3V Arduino Pro Mini’s and some XBee’s and will make some similar power usage charts of those; an XBee is ready to send in 35 milliseconds after power-up, so here the numbers will be quite different …

For those interested I’ve put together a page with some of the ESP power usage charts here, so you can see for yourself.

And now it’s time to move on … cause a new Odroid-C1 arrived on which I’m gonna play with OpenHAB, CometVisu, PencilBlue and some more interesting stuff 🙂