A multisensor LoRa end device has been designed for connecting different sensors to LoRa network. It’s primary use can be LoRa weather station but is not limited only to enviromental applications.
Typical “weather” application is shown in image above: 1-LoRa sensor interface, 2-Particle sensor, 3-Sun shield with temperature and humidity sensors, 4-UV-index and illumination sensor, 5-solar panel for autonomous operation. Different sensors will be described separately. I hope this project could grow into different directions.
I have some I2C sensors which are capable of running from low supply voltages. Host microcontroller has 3,3 or 5V supply, which is usually out of absolute maximum range, when I2C device is supplied with e.g. 1,8V. The sensor is usually very low power, which means simple emitter follower could do the low voltage supply.
The circuit schematic is shown in following drawing (click to enlarge):
2S Battery pack is very useful. It can be used to supply 5V electronic circuit without DC/DC. With help of a simple boost a 2S battery can drive 3 power LED lamp with reasonable currents. Etc…
Let’s see what is required for reliable, safe lithium polymer batter pack with two serially connected cells (2S LiPo battery pack).
Obviouslly, at least two cells are needed. Unfortunately, LiPo cells are very dangerous if used over specified limits. Most dificult is maximum cell voltage during charge. If cells are aexposed to voltages above 4,2V they can burn, but not at the charging, this could happen at any time after charging. The absolute maximum charging voltage is 4.25V per cell. To avoid burning down the house and other troubles, a battery protection circuit board (PCB) is a must with LiPo cells.