What board for battery powered 5V Sensors?

[bpair]

I have read over the battery powered section which uses a 3V Pro Mini. I was hoping to create a sensor that combines the following sensors

• Soil moisture sensor (3.3-5V)

• BH1750 Ambient Light sensor (3-5V)

• DHT22 Humidity/Temperature Module (3.3-5V)

I will only be recording data once every 10-20 minutes. For longest battery life would it be better to use a 3V Pro Mini( and I suppose I would need a step-up or bi-directional logic level shifter ?) or just go with the 5V Pro Mini?

I have never created a battery powered device so I am ot really sure what will happen as the battery drains. For example if the Pro-Mini needs a regulated 3.3v supply and it is connected to a battery what happens as the voltage drops below 3 volts?

[sundberg84]

Hi @bpair!
I have created a sensor with Light, Hum, Temp and Pressure. Maybe you can get some inspiration here...

To save power/battery its better to use 3.3v that 5v. When i make battery power i use this: my-2aa-battery-sensor when i wire and setup the sensor.

I use a 0.9-3.3v booster to suck the most out of the batteries, and this ensures 3.3v to the arduino until the battery is below 0.9v. You can the monitor the battery level 3.3v = 100% and 0.9v = 0%. Below this (or even 1-1.1v) the radio will fail and it will just be dead.

Also there is the Sensebender Micro http://www.mysensors.org/hardware/micro you can buy and use... it will probably last even longer but I dont know much about it since i dont use it at this time.

[bpair]

Thanks - your schematic/drawing is really helpful. I just ordered some of those step-up components and a few sensebenders.