Arduino Reptile data logger v2

After building the first data logger I updated it making some improvements. It now collects UV, temperature, and humidity data and then a second data temperature sensor provides data from a separate spot to the main housing. 

It uses an Arduino Nano for the board.

A BMP280 (Temperature) is used for the external sensor (I have it on a 50cm cable) in a 3d printed housing.

The DHT11 (temperature and humidity) and HW837 (UV) sensors are now mounted in the lid of the box.

The lid is secured with 5 M3 bolts.

There is now a Nano terminal block on the bottom to make wiring sensors easier.

This is fixed to the housing with 2 M4 bolts.

The BMP 280 has its own separate housing.

The DHT11 slides into recess in the lid.

I run this off of a power bank, but it could also run off of a wall charger.

Parts required

1 x Arduino Nano

1 x BMP280 temperature sensor

1 x DHT11 Temperature and humidity sensor

1 x HW837 UV sensor

1 x Nano Data logging shield

1 x 1220 battery (for the data logging shield)

1 x 32gb Micro SD card (I had this one to hand)

8 x M3 x 4 heat inserts 

4 x M3 x 10 bolts (for securing the lid to the housing)

3 x M3 x 5 bolts (1 for the BMP280, 2 for the HW837)

1 x M3 x 10 bolt (for the front of the housing to secure the lid)

2 x M4 x 4 heat inserts (in the base of the housing)

2 x M4 x 6 bolts (to mount the Nano terminals to the base)

Jumper wires

A 4 strand cable (for the BMP280) at the length you would like. I used 50cm.

Total cost was about $25 (plus printing) NZ when buying most parts from Ali Express.

Wiring

The BMP280 is wired through the side the housing. 

The BMP 280 and the HW837 are both powered from the 3.3v terminal and use the same ground pin. I did try both of these from the 5v and the DHT11 from the 3.3v but I had issues. Once swapped to this way round it all works fine. This is why the Nano terminals makes this so much simpler.

A wiring diagram is in the attached images.

Printing

I printed this in Polymaker black ASA. I used ASA for its resilience with higher temperatures and UV resistance.

I printed it with 4 walls and 40% infill.

All 3 files are oriented for the least amount of supports.

The only place I used any supports was on the lid for the slot for the DHT11.

This used just under 103g of filament to print.

Programming

The attached file needs to be uploaded to the Nano twice. The first time will set the Real Time Clock to the correct time. The second time you will need to comment out that line (line 45) so that the clock retains the correct time.

From then on it will record the data with the correct time and date.

If you would like to get the altitude data from the BMP280 I have only commented out that part of the sketch.

I have attached an example of the test data that I just collected. 

UPDATED 9/4/25

I found an error in the code. I have replaced the version on here with the corrected version 

Update 4/5/25

I ended up building 17 of these for some of the reptiles at work. Five had “Amega328p old bootloader” would work fine. Any with the “Amega328p” bootloader would not work with the external temperature sensor. That or the 2nd batch of data logging shields won't run the three sensors. I have also uploaded an additional code for no external thermometer. So unfortunately results with the external thermometer may vary, sorry.