Yl105 Datasheet -

A key detail missing from many quick-start guides is the jumper located near the optocoupler. This jumper determines the trigger logic:

Note: Some variants have a solder bridge instead of a jumper. Check your module carefully.

| Parameter | Value | |-----------|-------| | Operate Point (Bop) | 10–30 mT (South pole facing marked side) | | Release Point (Brp) | 2–15 mT | | Hysteresis | 5–12 mT | yl105 datasheet

Important: The YL105 typically responds to a south magnetic pole. Bringing a south pole near the marked face turns the output LOW (active low) or HIGH depending on the comparator circuit.

In hydroponic systems, sudden spikes in turbidity can indicate root rot or nutrient precipitation. The sensor acts as an early warning system before the plants show physical symptoms. A key detail missing from many quick-start guides

int hallPin = 2;
int ledPin = 13;
int hallState = 0;
void setup() 
pinMode(hallPin, INPUT);
pinMode(ledPin, OUTPUT);
Serial.begin(9600);

void loop() 
hallState = digitalRead(hallPin);
if (hallState == LOW)  // active low typical
digitalWrite(ledPin, HIGH);
Serial.println("Magnet detected");
 else 
digitalWrite(ledPin, LOW);
delay(100);
 Note: Some variants have a solder bridge instead

| Parameter | Value | |-----------|-------| | Supply Voltage | 4.5V – 24V (IC dependent) | | Output Sink Current | 25 mA | | Operating Temperature | -40°C to +85°C | | Storage Temperature | -65°C to +150°C |

The YL105 is a single-channel, opto-isolated relay module designed for interfacing with 5V logic systems. It allows a low-voltage microcontroller to switch an external circuit operating at high voltage (e.g., 110V AC or 220V AC) or high current (e.g., 10A at 30V DC).