Design Consideration_Power
The NodeMCU development board already has adequate power conversion 5V -> 3.3V and power conditioning (tantalum capacitors). Although probably overkill, I added an additional 470 uF electrolytic capacitor between VCC and GND pins to mitigate any voltage sag.
It is well documented that the ESP8266 is power hungry with potential high current draws (300 to 500mA) plus the device is sensitive to power fluctuations which can cause chip resets or other problems. Furthermore, the analog thermistors and ADC may be impacted by power rail noise.
To mitigate this, I've deisgned an option to add a "power input filtering subcircuit" that I came across here which consists of an axial inductor in series with a small resistor followed two capacitors in parallel. This Lowpass RLC Filter configuration is intended to filter out high frequency noise and stabilise voltage fluctuation. Basically the inductor blocks AC and the two capacitors shunt higher frequency noise to ground. One Arduino forum member suggests the very small 1-10 ohm resistor (RP) in the RLP filter is unnecessary as the inductor choke has enough resistance on its own. To Do: measure inductor resistance on DMM
Given I'm using a stepdown 3.3V AMS1117 based power module where the LDO regulator already has smoothing capacitors built into the modules, this level of filtering and power regulation is probably overkill. Because of this, I'm designng the board so that I have the ability to add these extra power filtering components at a later time if it turns out they are needed.
