Hardware_Parts Selection_Power
I had planned to use a Jackery Giant+ 5V battery bank that I already own and have successfully used for other projects such as powering a dew heater for Milky Way star photography. The (nominal) 1200 mA-hr Jackary Giant+ has both 5V 1A and 2.1A USB jack outputs. I previously built a power cable that I will reuse which has a male USB power jack on one end, a 2A inline fuse and a male DC power jack on the other end.
The Jackery Giant+ has an auto power-off feature designed to conserve the battery life. Given this project does not require a constant power draw, if left as-is, this feature would make this battery unsuitable as the battery would power off between temperature measurements. However, I have built a low-duty cycle oscillator designed to plug into one of the USB ports and defeat the battery's auto-off circuitry. See Low Duty Cycle 555 Oscillator for details.
Once, the prototype was constructed, I realised that the Jackery powerbank was far too large and overkill for this project. The cloudSmoker only draws ~350mA peak, meaning that a much more compact Moki brand, 5,000 mAh powerbank could power this for a minimum of 10 hours.
(5000 mAh * 3.7V / 5V) / 350mAH = 10.5 hrs
manufacturer stated Powerbank capacity is based on cell voltage (nominal 3.7V) and must be corrected for output voltage
Actual average cloudSmoker current draw is far less than peak draw and, in practice, I used less than 20% of the Moki powerbank's charge over an 11-hour period. Given I had ample power for a long cook, I dropped my plans for implementing low power sleep on the ESP8266 which also had the advantage that I no longer had to defeat the powerbank's auto-off features.
Although the adaptor plate has pads to solder on a simple AMS voltage regulator, I chose to purchase a step-down converter module that will take my 5V battery down to the 3.3V required by the ESP8266.
The step-down module is based on a low dropout regulator (LDO) approach using an AMS1117-3.3 LDO Chinese clone. As such, it is not as efficient as a true buck module where power is stored in an Inductor. Nevertheless, given the the small required voltage drop (5V -> 3.3V), the wasted energy as heat will be small. This step-down module has power filtering capacitors built in as well as a power-on LED.
The schematic below shows the basic configuration of this module except the module I have does not have separate input and output headers. If necessary, the LED and associated current limiting resistor (marke R1 = 1k ohm) can be removed to further power drain on the battery.
