DHT11 is a humidity and digital temperature sensor. It comes under the classification of weather sensors. The sensor gives out a digital signal based temperature and humidity output. DHT11 consists of an NTC, 8 bit microcontroller and resistive sense of wet components.
DHT11 calculates humidity by measuring resistance between the electrodes
This is a GSM modem which has a serial interface and plug and play facility. The modem can be used to send SMS, receive and make the calls, and do the basic GSM operations with the help of AT commands. A standard RS232 interface is used so that we can use it to interface with microcontrollers and PCs. It has power regulation, SIM
HC-05 module is an easy to use Bluetooth SPP (Serial Port Protocol) module, designed for transparent wireless serial connection setup.
Serial port Bluetooth module is fully qualified Bluetooth V2.0+EDR (Enhanced Data Rate) 3Mbps Modulation with complete 2.4GHz radio transceiver and baseband. It uses CSR Bluecore 04-External single chip Bluetoot
A caster wheel (or castor) is an undriven, single, double, or compound wheel that is designed to be mounted to the bottom of a larger object (the "vehicle") so as to enable that object to be easily moved. They are available in various sizes, and are commonly made of rubber, plastic, nylon, aluminum, or stainless steel.