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1 Arduino + 3 or 4 LM35s? Answered


I am a total beginner, having logged about one hour here (the last hour).

Does this sound OK for a first Arduino project?

I want to sample and log the temperature outside at the surface and at depth for a total of 4 readings to a depth of around 50cm (20"). The reason is to consider if I should provide my daughter's pet rabbits with an underground burrow as relief against the next heat wave. It seems a nicer option than running a swamp cooler all day. Though I suppose I could use an Arduino + LM35 to turn on and off the swamp cooler :)

It looks like I can do it with 4 x LM35s, an Arduino One, some sort of data storage, a 9v battery and a bread board.

Any recommendations for if I should use WiFi or an SD card for storage? My guess is the SD card is simpler to programme and maybe less of a battery drain.

It seems I just need to hook up the data out of the LM35s to the analogue ports, then loop over the inputs and write the outputs to a file somewhere. And calibration too.

Any pointers on how to turn the LM35s into probes that can be buried in the ground? I was thinking I could bind all the probes onto a dowel, dig a hole and bury it.

How to extend the LM35 pin outs?

Thanks in advance for any suggestions.

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steveastrouk (author)2017-04-12

The LM35 output is very tolerant. You could daisy chain the supply to all 4 of them, and just bring back their outputs, so you'd only need 6 wired to your dowel. If it were me, I think I'd glue them though the wall of a thin PVC pipe, then drive that into the soil.

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