Sunday, March 25, 2018

New wireless mini node

Lately I have stared to play even more with various remote sensors wirelessly
connected to OHS gateway. I have used my standard radio nodes, but its versatility is somehow to much for small wireless node. To save space and gain easier access to pins of MCU I have designed new node called Radio Node Mini. It resembles Arduino Pro Mini with ATmega328P, but it has place to mount RFM69 board on it. It also has micro USB connector for charging designed for 3.7 Li-Po or Li-On battery.

It is breadboard friendly and measures only 24.4 x 32.8mm (0.96 x 1.29 in). All available pins are taken out to board sides and marked as on Arduino board. It is 3V3 board and it is available with 16Mhz or 8Mhz quartz oscillator. As it is made to work with Li-Po or Li-On battery it features battery voltage measurement on A6 via 2:1 voltage divider, and also ability to detect charging state connected to pin D8. Pin D2 is not taken out as it will be used as interrupt pin for RFM69. It has also possibility to assign pin D4 as reset for the RFM69 via solder jumper labeled RR. Board is programmable via FTDI programmer. Note, that it is not able to take power from micro USB without battery, the charger is providing only minimal current to the board when it does not detect the battery. However FTDI programmer can be used also as power source while developing.

Board has excellent standby battery consumption within few uA when MCU and radio is asleep. It will last for months to year(s) depending on battery size and sleep conditions. Board is able to handle 500-2000mA battery. I especially like those flat 700-800mAh small quadrocopter batteries found on eBay. they are cheap, has similar size as the board, and have also protection circuit built in. Only drawback is that they have usually 100-150mAh less capacity then advertised.

Boards are also now available in my store for 7EUR fully assembled. As option you can choose radio module, pigtail and antenna.