1 Arduino + 3 or 4 LM35s?

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.

steveastrouk2 months ago

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.