Day 18: Candle Alarm
And today we have a small diode waiting behind the door. We are going to use the diode as temperature sensor for particular high temperatures and with it we will build a small candle guard.
Today’s setup consists of the diode and the potentiometer, which we will use as a 10-kOhm resistor. This resistance is fixed and cannot be adjusted. The board will measure the voltage at the diode and sends the values to Node-RED via MQTT.
Today’s flow is continually evaluating the measured value. If the value falls below a certain value (the higher the temperature, the lower the measured voltage), an alarm is output in the form of a read-out text message and an info box. You can set a threshold for the alarm in the user interface. Place the diode near the lower part of a candle in such a way that the flame is near to the diode as it burns down and you have got a very handy detector for a candle that has burnt down to the bottom.