Weather Station Pi
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The DHT11 sensor is a capacitive humidity sensor and thermistor that measures the surrounding air and can connect to the Raspberry Pi to send this data on the data pin. The capacitive humidity sensor consists of a material that can absorb moisture from the air (hygroscopic), and a material that is usually an insulator that becomes a poor conductor of electricity (dielectric) when close to an electric field. In the absence of moisture, the 2 materials are in a neutral position so there is a constant position the materials will remain. In the presence of moisture, the current changes because of the hygroscopic material absorbs some of the moisture and the dielectric material changes the level of electric conduction. This change is read by the sensor and converted into a percentage depending on how much resistance the materials offer. The thermistor works on a similar principle, where the electrical resistance of changes depending on the surrounding temperature. Usually the resistance lowers when the temp increases which can be detected by the DHT11 sensor and then transmitted through the data pin to the Raspberry Pi.
Secure Shell (SSH) is the best way to connect securely to a Raspberry Pi, this only allows for CLI interactions but makes the communication very secure. By default, SSH is usually configured to work on port 22, which can be determined using a nmap scan of the network and for Raspberry Pi’s the default logins are username: pi and password: raspberry. SSH uses asymmetric encryption in the data transfer process, for a connection to be made the public key needs to be 1st generated by the Raspberry Pi (make sure the default SSH credentials have been changed) and then shared to anyone trying to connect to the SSH port. Once the public key exchange has occurred and confirmed by the SSH server (Raspberry Pi) the asymmetric connection is created, encrypting the traffic that is sent to the client and decrypted because the credentials are confirmed on both ends of the connection. SSH is a vital network protocol that secures a lot of IT professionals communications between admins and secure servers. Linux based OS have SSH clients built into them, but Windows doesn’t, make sure the students have an SSH client like PuTTY installed and know the IP address of the Raspberry Pi to connect to it.
Suggested Year Group
The suggested age group is 14+, due to the nature of this project and the skills it is developing.
Instruct the students how the DHT11 sensor works;
Show the students how to connect the DHT11 to the Raspberry Pi;
Illustrate how SSH works to create a secure connection to the Raspberry Pi.
Component Number (Peli Case)
(Base) 4 + 5
(Level 1) 3
(Level 1) 3
(Level 1) 3
(Level 1) 5
(Level 1) 1
Component Number (Box Case)
Raspberry Pi + Case
Raspbian SD Card
Male Female Wires
This project could allow both internal and external temperatures and humidity to be tracked using the SSH connection between the Raspberry Pi and a remote connection. This is a very secure way of communicating with the Raspberry Pi, if the default username and password have been changed. There are many ways this project could be adapted, an LCD screen could be connected, email notification if the temperature was too high or humidity too low. Instruct the students to explore different applications of physical computing and how different problems can be fixed/helped with the right mindset. SSH is a very important network protocol, this has allowed more security when connecting to remote devices. Older protocols like Telnet didn’t include as rigorous security standards like SSH which makes SSH a much more desirable method of network connection.