The obstruction circuitry is missing a 10k resistor between the D7 pin and ground. The combination of a resistor in series and resistor to ground acts as a voltage divider, therefore reducing the voltage seen at the D7 (GPIO13) pin to a save ~3.3 volts.
Without this resistor to ground, the voltage seen at pin D7 exceeds the ESP8266 specifications, however the prototype was lucky in that there is documentation on the ESP8266 which mentions that it has some internal protection that shunts excess voltage to protect the chip even though it is only supposed work with 3.3v.
The obstruction circuitry is missing a 10k resistor between the D7 pin and ground. The combination of a resistor in series and resistor to ground acts as a voltage divider, therefore reducing the voltage seen at the D7 (GPIO13) pin to a save ~3.3 volts.
Without this resistor to ground, the voltage seen at pin D7 exceeds the ESP8266 specifications, however the prototype was lucky in that there is documentation on the ESP8266 which mentions that it has some internal protection that shunts excess voltage to protect the chip even though it is only supposed work with 3.3v.