Different Type Of Sensor

          Different Type Of Sensor

MQ-2 Gas Sensor

         

The MQ gas sensors can detect different gases at room temperature. Depending on the model, other gases are supported. The MQ-2 can recognize methane, butane, LPG and smoke, the MQ3 detects, for example, alcohol, ethanol and smoke, etc. 

You should take care that these sensors can be very hot and they should not be touched directly. Since these modules also work analogically with 5V, you need also a MCP3008 as well as a 3.3V-5V TTL to read the signals.    

PIR Motion Sensor

The PIR motion sensor has some advantages over other similar products: besides the low price, a signal is sent only if something moves. This allows you to wait for signal flanks using the GPIOs. In addition, a resistance can be varied so that a signal is only sent when the movement is close, or changes that are already far away are perceived.

In addition to outdoor projects, the PIR can also be used in buildings – whether to activate the lighting or, as I use it, to turn on my touch screen for home automation as soon as someone approaches it.

Moisture Sensor

This analogue humidity sensor finds an excellent place in automatic irrigation systems. It is placed in the ground and measures the humidity by current flowing between the strands. The more humid the earth in between, the higher the (analog) signal. In order to read the value with the Raspberry Pi, the MCP3008 is needed (Arduinos can recognize analog signals directly).

     

HC-SR04 ultrasonic sensor

The HC-SR04 sensor is not a distance / motion detector, but an ultrasonic sensor. Through a small trick it is nevertheless possible to measure distances. By measuring the time elapsed between transmitting and receiving an ultrasound signal, you can derive the distance as the sound velocity in the air is known. The wide opening angle is an aspect which, however, must be considered: since the ultrasound propagates not only on a straight line, but at an angle of about 15°, the signal is first reflected from the nearest point in this area – which can be also an external point.
As a rough estimate, or for moving robots, it is nevertheless useful, also because of the low price.

Raindrop Sensor

In order to determine whether it is raining or how much rain is present, a rainwater sensor can be used. It works analogously and can be read with the MCP3008. Depending on the amount of water, the capacitance is increased and a stronger analog signal is read out.

DHT11 / DHT22

The DHT11 and DHT22 sensors can measure humidity as well as temperature. Only one GPIO is used. The difference between the two is mainly the measuring range and accuracy. The white DHT22 can measure all humidity ranges from 0-100% with an accuracy of 2%. By comparison, the DHT11 (blue) is only able to measure areas of 20-90% humidity and above all, the accuracy is significantly worse with 5%. The light blue DHT11 sensor has a small price advantage.