Temperature and humidity sensor - battery powered

I made a temperature and humidity logger. Now I know there are probably thousands of loggers around, but this one was designed to have very low power consumption, which isn't really possible with a development board and a shield on top.

During idle mode (almost all of the time) it only uses around 6 µA to 7 µA of current. This means it should be possible to power it from batteries for a long time.

Readings are taken every 15 minutes and logged to a tab-delimited file on the micro-SD card. This can then be imported into a spreadsheet, eg.

Schematic and detailed design descriptions here:

http://www.gammon.com.au/forum/?id=12106

[quote author=Nick Gammon link=topic=181180.msg1342808#msg1342808 date=1375697983] I made a temperature and humidity logger. Now I know there are probably thousands of loggers around, but this one was designed to have very low power consumption, which isn't really possible with a development board and a shield on top.

During idle mode (almost all of the time) it only uses around 6 µA to 7 µA of current. This means it should be possible to power it from batteries for a long time.

Readings are taken every 15 minutes and logged to a tab-delimited file on the micro-SD card. This can then be imported into a spreadsheet, eg.

Schematic and detailed design descriptions here:

http://www.gammon.com.au/forum/?id=12106 [/quote]

You have got to be retired with the amount of code and products you churn out !!!

I hope you are not on a pension and i am supporting you XD XD XD

Craig

Great project for 6 µA to 7 µA really.

DS1307 seems to drift too much, did you consider to use another RTC?

Did you consider to add routines to set Time in RTC?

[quote author=Nick Gammon link=topic=181180.msg1342808#msg1342808 date=1375697983] I made a temperature and humidity logger. Now I know there are probably thousands of loggers around, but this one was designed to have very low power consumption, which isn't really possible with a development board and a shield on top.

During idle mode (almost all of the time) it only uses around 6 µA to 7 µA of current. This means it should be possible to power it from batteries for a long time.

Readings are taken every 15 minutes and logged to a tab-delimited file on the micro-SD card. This can then be imported into a spreadsheet, eg.

Schematic and detailed design descriptions here:

http://www.gammon.com.au/forum/?id=12106 [/quote]

Nick, just read through the online link - very elegant the solutions with the power down on the switched 5v bus

Your data in the spreadsheet and the graphed data does not matched the description given in the code for time intervals - i assume this was earlier test code and readings ?

Craig

zoomx:
Great project for 6 µA to 7 µA really.

Thanks. :slight_smile:

DS1307 seems to drift too much, did you consider to use another RTC?

I didn’t consider the exact time to be critical. The general question is, how much does the temperature/humidity vary, over time. Even if the clock was an hour out, you would still get the general idea.

Did you consider to add routines to set Time in RTC?

Since it would be deployed “in the field”, not really. However I suppose with another switch you could have something like “press once to enter setting mode” like you do for a watch. Nice idea for a future version.

craigcurtin: Your data in the spreadsheet and the graphed data does not matched the description given in the code for time intervals - i assume this was earlier test code and readings ?

Yep, I was initially testing on change of minute.

[quote author=Nick Gammon link=topic=181180.msg1342890#msg1342890 date=1375701467]

craigcurtin: Your data in the spreadsheet and the graphed data does not matched the description given in the code for time intervals - i assume this was earlier test code and readings ?

Yep, I was initially testing on change of minute. [/quote]

Aaah ! Not going to make a case for it to hide the inner workings ?

Craig

I know! I should have used a state machine and got rid of the delay() calls!

I see the error of my ways now. :P

[quote author=Nick Gammon link=topic=181180.msg1343801#msg1343801 date=1375743677] I know! I should have used a state machine and got rid of the delay() calls!

I see the error of my ways now. :P [/quote]

I would not think to correct a god like being such as yourself !!!

but good call :grin: :grin:

Craig