Project Evolution

This page is intended for those who want to build wireless monitoring on their own - perhaps without any PCBs or kits that I may be offering. It describes the prototypes that led up to the finished project shown on the Wireless Monitoring page. I thought these notes might be helpful for anyone wanting to build wireless monitoring from scratch.

There were two stages of prototyping:
  1. Without PCBs - This used the Adafruit Logging Shield for the SD card and time clock on the Display Station side.
  2. Basic PCBs were made to make it easier to connect the RFM22B transceiver to the Geiger Kit and the Adafruit Logging Shield.
The first prototype was built using off the shelf components and the Geiger Kit. 

The Outside Sensing Unit

The sensing unit is the Geiger Kit running at 3.3V, interfaced to an RFM22B transceiver via SPI. I wanted it powered by a solar cell so I used the Adafruit Solar Charger that keeps a 2700mAh LiPo battery charged. However it can be powered by batteries only.

For the first prototype, I used the RFM22B transceiver without the breakout board by bending pins on a header and soldering directly to it. Not pretty, but worked fine. The headers were then connected to Geiger Kit. 

As with the finished project, the UC_PWR jumper on the Geiger Kit is removed, separating the Vcc that powers the HV circuit from the ATmega328. The sketch controls the power to the Geiger circuit through an I/O pin. Using the Geiger circuit only when needed saves power.

Software-wise, the sensing unit should be able to have the same same functionality as the finished project. You can get an overview of the functionality and download the current sketch from the Wireless Monitoring page.

The Display Station

For the first prototype, the display station was an Arduino running at 5V from a power adapter. For the SD card and the RTC I used the Adafruit Logging Shield. The logging shield had the necessary buffer to run the 3.3V SD card at 5V. Connected to the breakout pins on the logging shield is an LCD, menu buttons, and another RFM22B transceiver. Like the SD card, the RFM22B is a 3.3V part. This means that another 3.3V chip select line is needed. For this I modified the Adafruit Logging Shield to make use of an unused buffer for CS pin of the RFM22B. (The MISO, MOSI, and clock lines are shared between the SD card and RFM22B). If you are interested, I have her modified Eagle files here.. 

Software-wise, the display station should be able to have the same same functionality as the finished project. Again, you can get an overview of the functionality and download the current sketch from the Wireless Monitoring page.

Moving to Preliminary PCBs
After the first prototype I designed some boards to make it easier to build. One attaches to the Geiger Kit and the other to the Adafruit Logging Shield. The purpose of these boards is to:
  • hold the RFM22B transceivers on both pieces so you can save money and buy them without a breakout board
  • provide a 3.3V regulator to power the Geiger Kit (the solar charger output is not regulated)
  • provide the extra buffer (74HC125), LCD & pot, menu button circuit, and piezo on the Adafruit Logging Shield
  • basically clean up a lot of the connections
Here is what they looked like . . .

The board on the left, goes over the Geiger Board and the board on the right, goes over the Adafruit Logging board.

Here is a view of the PCBs connected . .

Later I realized that the design of the display station could be streamlined quite a bit by making a single board that replaces the Arduino, Adafruit Logging Shield, and the shield that sits on top it. This was the final stage of the project described on the Wireless Monitoring page.