#8 candle snuffer

this week i wanted to start with a simple input device, and decided to look into simple photo resistors. they are, as the name says, resistors that are light sensitive. if not exposed to light, they can have a high resistance, while, the brighter light they are exposed to, the lower their resistance.

I decided to make a small pcb, that simply allows me to connect an analog sensor, like the photoresistor, and added an additional led on the board, that could be triggered through a digital pin depending on the analog input

so i decided to make some new pcbs to test the idea.

the original idea was to create a pcb that functions with a microcontroller, and another one that would be a completely analog circuit.

in the experiment, i connected my new pcb to my esp32c3, using one analog, one digital, the 5V and GND pin. I would be reading the analog resistance difference through the analog pin, and would send different blinking signals to the digital pin, that is connected to the led on the board. (this example was running a micropython script through thonny)

i use the phone led to test the threshold of the analog signal, so it does not react fully by the environmental light in the room.

from machine import ADC, Pin import time photoresistorPin = ADC(4) ledPin = Pin(5, Pin.OUT) threshold = 5 while True: lightLevel = photoresistorPin.read() print(lightLevel) if lightLevel < threshold: ledPin.on() else: ledPin.off()

and based on the led example, i thought it would be fun to have it react to a flame of a lighter, maybe eventually of a candle. So if i connect an led, it will turn on when the candle burns down, but is shut off as long as the candle burns.

I tried looking at the serial plotter in thonny, but it picked up a lot more noise than the previous arduino code did, so i brought this back into arduino and used/recorded the serial plotter in arduino.

here is the code i used in arduino:

const int photoresistorPin = A0; const int ledPin = 9; const int threshold = 100; //threshold value for light level void setup() { pinMode(ledPin, OUTPUT); Serial.begin(9600); } void loop() { int lightLevel = analogRead(photoresistorPin); Serial.println(lightLevel); if (lightLevel < threshold) { int blinkSpeed = map(lightLevel, 0, threshold, 100, 1000); digitalWrite(ledPin, HIGH); delay(blinkSpeed); digitalWrite(ledPin, LOW); delay(blinkSpeed); } else { digitalWrite(ledPin, LOW); } }