Hello everyone, for a university project I am supposed to read the analog signal of an inductive sensor SIM618-73 and output the signal 0 or 1. The sensor is an AC 2 wire normally open contact. I am using an Arduino UNO and the sensor is running at a minimum of 20V. I have now connected the sensor to a voltage converter that supplies it with 24 volts on the two wires. Now I have the problem that my Arduino of course can only handle 5V on the AnalogPin. So I tried to build a voltage divider on it. But unfortunately that didn't really work out. On the internet I found very little information about the connection of a 2 wire sensor with an Arduino and I am desperate since several days. Basically I have a problem understanding which of the 2 wires I should wire. I thought of such a circuit diagram, but without the GND cable.
The absence of a ground connector is what is stopping it working.
A better circuit is if the 10K resistor R8 is connected to the collector and 5V, and D6 is connected to the transistors collector.
The way these sensors work is that they draw some current from the 24V Source, and when they are in proximity of metal ( or of a large capacitance depending on the type of the sensor ) they draw more current.
So the way you interface them is to give then 24V and a load resistor from the output to ground, with the load resistor connected to the Arduino ground. This load resistor can be in the form of a potential divider with the lower resistor being connected to the Arduino.
However, if you have the type 5 sensor like the highlighting seems to indicate, it still works the same but it is connected to mains. In this case you would need an isolation transformer on the output, with a bridge rectifier and large capacitor and a burden resistor. Then look at the DC output of this to see how the signals change in response to proximity of the metal.
These type of sensors are known as Klockner Moeller proximity sensors. I used to work with them with my first job after leaving school in the mid 1960s.
These are not always available, and will be more expensive. The operation is simple. The windings of an inductor are turned into a tuned oscillator. With the presence of metal the effective inductance increases so moving the resonant circuit away from the tuned frequency. This causes the oscillator to stop and so the circuit draws more current.
Think of it like an electric motor. While it is running it is taking little current, but you put a load on it so that it stalls, then It draws a lot of current.
