This assembly will detect the presence of water on a sensor. It can be placed in any room of the house where it is useful, that is to say near water-consuming appliances. A leak detector consists of a case containing the system power supply, the system itself and a sensor connected by two wires to the case.
What supplies are needed?
- Cutting pliers
- Copper wire
- Wire stripper
- Tin spool
- Soldering iron
1. In addition to the listed supplies, you will need electronic components from:
- 12,000 Ohms
- 100 Ohms
- 560,000 Ohms
- 8,800 Ohms
- 2,200 Ohms
2. Realization of the sensor
The sensor is a passive sensor. No particular component is needed.
– Reproduce on a single-sided epoxy plate of size (10 cm x 10 cm) 5 horizontal stripes.
– Weld green wafers with copper wire of sufficient length to connect the housing.
The principle of this sensor is as follows: in a normal situation (no leakage) the resistance between the two green pellets is infinite because there is no contact. If the detection is positive, namely the presence of water on the sensor, the resistance of the sensor decreases strongly allowing the passage of an electric current.
3. Perform the electronic assembly of the detector
Wire an operational amplifier type TL 081 as a voltage comparator. This comparison is made between two voltage divider bridges. The first bridge on the inverting input serves as a “reference,” the potentiometer is used to adjust the sensitivity of the device.
The second bridge consists of a fixed value resistor and the water sensor or detector. If the resistance of this sensor decreases (presence of water) the input of the operational amplifier is almost grounded.
A current is then generated at the output of 741 which is amplified by an entirely conventional transistor, type 2N 1711 for example.
The resistor R3 serves as a loopback while the resistors R4 and R5 form the divider bridge of the transistor mounted as a common collector.