KEY FEATURES OF FLAME SENSOR MODULE:
Detects infrared in the spectrum produced by an open flame
Provides both an analog and digital output with a sensitivity adjustment
3.3 and 5V compatible
This sensor module is primarily used to detect an open flame.  It does this by detecting light that is in the IR (infrared) spectrum which is emitted by a flame.  That spectrum is typically in the range of 700-1100nm.
This module is similar to a regular IR detector, but with a broader detection range.  It can be used as a general IR detector for other applications where a broad detection range is desired.
Outputs
The module has both an analog output and a digital output with sensitivity adjustment on the module.
The Analog output on ‘A0‘ is normally a voltage of approximately 1/2 Vcc when no signal is detected.  The actual voltage level will depend on the setting of the sensitivity pot. If a flame is detected, that output voltage will drop towards ground depending on the strength of the IR detected.
The Digital output on ‘D0‘ is normally LOW.  When IR is detected by the sensor, the output goes HIGH.  The sensitivity adjustment can be used to set the trip point.  LED2 will light when the output goes HIGH.
Module Connections
There is a 4-pin header on the assembly.
GND  = Ground
‘+’ = Vcc (3.3 – 5V)
A0 = Analog output, connects to analog input on uC
D0 = Digital output, connects to digital input on uC