Building a Wireless Sensor Network with the nRF24L01 Part 2

[@itisonlyadream]

The battery power consumption issue is rarely addressed and you packed so much practical and useful information into your excellent explanation. This video will be my "go to" reference when doing all my battery powered Arduino projects.

[@BGLENN-dp4tx]

These videos are rich in content. Thanks for the superb effort.

[@omaryanas435949]

awesome video ! looking forward for part 3.

[@ulysseintel647]

Hi, thank you for this very interesting course. i noticed, the resistor divider consumes current every time. Typically let's say 3V/(560K+180K) = 4uA . (6.6% of 60uA power consumption). It is possible to avoid that, for instance by connecting R1 to an output and only enable it when you do the measurement. Another point, you can remove the resistor connected to the switch by using AT328 internal pull-up resistor instead. Now I am going to follow the next part of this interesting course ;-)

[@ForceTronics]

Thanks for the great input. As you will find later in the series there is a way to avoid the resistor divider approach and measure it using the known internal ADC reference value.

[@ElAMPox]

If you are connecting the AVR directly to the battery, you can put the positive side of the voltage divider on an unused pin and just turn it on when you need to make a read. Beware that there is going to be a small voltage drop but you can compensate for that.

[@skynet47110815]

great work.i like the voltage monitoring. *thumbsup*

[@lrlinnell]

Love the series! In Part 2, you discussed measuring Vcc using the resistive divider and the internal 1.1v ref. You measured the actual values of your two resisters and calculated a "divide factor" that was to be stored in EEPROM. I have measured my two resisters but don't see where to input them. The fReadVcc() function does not appear to use any "divide factor". Am I looking in the wrong place?

[@ForceTronics]

+Lloyd Linnell There is a comment in this thread where RoterFruchtZwerg let's me know that there is a way to check the battery voltage using the internal ref and just the ATmega328p without have to add a voltage divider or use up an analog pin. I make an update to the design in a later part (3 or 4) where I give the details of the update and the method. Long story short I take out the voltage divider and therefore you don't need the resistor voltage divider cal factor.

[@lrlinnell]

+ForceTronics awesome! two less components. must have missed that one. thanks

[@davidjenkins8675]

I hope you are intending to (or we can) use the arduino clones instead of a breadboad. Our meetup group has found that the clones are cheaper than the parts. Additionally, I would not want to expose a breadboarded unit in the field. Having used your boards I like them but I like to use off the shelf products available. There are rugged versions of the arduino avalanche as well . 600 days plus for the transmitter batter is really great and opens a lot of opportunity for us.

[@ForceTronics]

+David Jenkins I totally agree, the breadboard is just for prototyping purposes. I plan to do a custom PCB board layout for this design using Eagle software (free for hobbyists) which will probably happen in part 4. Once complete I will share the files on GitHub for other to use.

[@omaryanas435949]

Hi, any thoughts on when part 3 is coming? Looking forward to ur cool explaination of the code. Cheers :)

[@ForceTronics]

+Anas Omary This evening (US mountain time)!

[@DiyintheGhetto]

Hello it would be nice to actually see the voltage in the serial monitor instead of a 1 or a 0. But other then that awesome video.

[@wailingpeanut]

Hi, Great video!! I just had a quick question. On your battery power needs, you calculated 55.84 uA based of 600 seconds. You used 60 uA per hour for average. I was wondering wouldn't it be 60 uA x 6 to get the power consumption for 1 hour instead of using the 60 uA that you rounded up for 600 secs(10 mins)?

[@ForceTronics]

+wailingpeanut I am calculating amp hours (which I probably should have labeled better). The design cycles every 10 min so I use that to get its average consumption per cycle. It doesn't mater how many cycles occur in an hour whether it is 6 or 60 its amp hour usage is 60uAh.

[@JBaza1126]

Sorry for commenting on an old comment but can you explain this a little more for a beginner. Im lost in this concept, wouldn't transmitting more cycles in an hour pull more than 60 uA?

[@ForceTronics]

The unit of measurement is not 60uA it is 60uAh. This stands for 60 micro amp hours which is a measurement of average current consumption over an hour.

[@explosive2005]

Thanks for this explanation. I've been trying to figure this out for days

[@TonyStark-uz6qs]

can we use cr2032 or a different model of coincells for power?

[@ForceTronics]

sure if it meets the 2.5v to 3.6v range

[@mamdobreklapki0]

I got the same idea:) We can use it for powering nrf24l01 and add another in series to reach 6v.. to power arduino and ds18b20 :)

[@RoterFruchtZwerg]

Did you know the 328P can measure its internal 1.1V reference against AVcc? This way you can measure your battery voltage without additional circuitry: code.google.com/p/tinkerit/wiki/SecretVoltmeter

[@ForceTronics]

+RoterFruchtZwerg Thanks for the info, I will check it out!

[@RoterFruchtZwerg]

+ForceTronics I'm using this method on many projects. Having an Arduino Pro Mini 3.3V (8Mhz) reading its Vcc and Temp/Humidity from a DHT22 every 5min and broadcasting it using a NRF24L01. It's powered by a standard 1.8Ah Li-Ion cell (which has 4.2V fully charched btw) for more than a year now. Only modification I made to the Arduino board is removing its power led. Since I use the 3.3V regulator I cannot measure the battery voltage directly, but the 3.3V will start to drop when battery goes below ~3.7V which is still fine. My circuit goes to permanent sleep at 2.8V Vcc which is ~3.2V battery voltage.

[@ForceTronics]

+RoterFruchtZwerg I plan to update the project using this method to track the battery voltage. Thanks again for sharing it!

[@Graham1904]

Surely 60uA for 10 minutes not per hour.

[@ForceTronics]

I don't quite understand this comment. I use a 10 min capture of current to get an average current value over that 10 min. I then make the assumption that an hour would have the same average current. I then use that current value to do an amp hour calculation on battery life (10 min avg current is 60uA therefore assuming 1 hour also has 60uA average current so amp hour current consumption is 60uAmp hours).

[@siradekunlenicholasadefela3154]

thanks for this actually you have done a great job i prefer messaging you privately please can i have you emai

[@ForceTronics]

I am glad you enjoyed it. Sorry I do not provide my private email, I get a lot of requests and do not have the bandwidth to communicate one on one.