To build the data logger you need a few components. The next sections will list the main components for each version of this project. I assume you are familiar building electronic devices and own all necessary tools.
The Minimal Version
- Adafruit Pro Trinket 5V
You can also use an Arduino Pro Mini, or an Arduino Nano 3.x. Both will work fine but check you connect the right pins. You should be able to use my software without changes,but you have to setup the Arduino IDE differently.
- Adafruit PowerBoost 500
This is an optional component. You can e.g. power your device from alkaline batteries, but it will require a different wiring.
- AM2302 (wired DHT22) Temperature/Humidity Sensor
- Lithium Ion Battery Pack – 3.7V 6600mAh
For this project it has to be minimum 9cm × 6cm.
- 10 kΩ Resistor
- BCD DIL Switch
I use the SC-2010W from Copal Electronics
- 2x Slide Switch on-on
I use the 600A-611-M2R from Taiway for the power switch and the SS12SDP2 from NKK for the charge connection.
- Crimps and Crimp Socket
I use them to attach a connector to the sensor.
- Various Pin Headers
- Various Wires
I use 0.50 mm²/ø0.20 mm wire in many colours.
Important Note: If you plan to reuse the components on the breakout boards, you also need female pin headers to make them removable. If you solder the components directly on the stripboard it is almost impossible to remove them afterwards.
The Simple Version
The simple version just adds more memory and increases the precision of the recorded data.
I am using FRAM instead of flash memory, or even an SD card, because writing to FRAM needs way less power than writing to flash RAM. It is also faster, which increases the “sleep” time for the microcontroller. The only catch of FRAM is, it is more expensive than flash RAM.
My software has a simple abstraction of the used storage, so you can simple replace the FRAM with a flash chip (e.g. like this one).
Continue reading: Build the Hardware