The MQ series of gas sensors use a small heater inside with an electro-chemical sensor. They are sensitive for a range of gasses and are used indoors at room temperature. The output is an analog signal and can be read with an analog input of the Arduino. The MQ-2 Gas Sensor module is useful for gas leakage detecting in home and industry. It can detect LPG, i-butane, propane, methane ,alcohol, hydrogen and smoke.

 

This is a 12V 1-Channel Relay interface board which can be controlled directly by a wide range of micro controllers such as Arduino, AVR, PIC, ARM, 8051 and so on. It can control both AC and DC appliances such as Solenoids, Motors, lights, fans, etc High quality screw terminals (Terminal Block) provided (C, NC , NO) for quick and easy connection LED Status indicators to indicate the relay ON/OFF status.

The 8 channel 12V relay module provides 8 optically isolated inputs that accept a wide range of voltage. This is a great way to switch on or off AC or DC loads using your Arduino. The relays are single-pole double-throw (SPDT) and are rated for 10A @ 250VAC. The ground for the relay coils is separate from the ground for the input signals. This, along with the optical isolation, provides a total galvanic isolation between the input and output. The two grounds could be joined together if desired with the included jumper. The relay coils run on 12VDC, and the module has screw-terminal blocks for sturdy and reusable attachments for the external load. The signal and power inputs run through the male single-row header.

DTMF Refers to Dual Tone Multi-Frequency Signaling. This DTMF is used for telecommunication signaling over analog telephone lines in the voice-frequency band between telephone handsets and other communications devices and the switching center.

The TCS230 programmable color light-to-frequency converter combines configurable silicon photodiodes and a current-to-frequency converter on single monolithic CMOS integrated circuit. The output is a square wave (50% duty cycle) with frequency directly proportional to light intensity (irradiance). The full-scale output frequency can be scaled by one of three preset values via two control input pins. Digital inputs and digital output allow direct interface to a microcontroller or other logic circuitry. Output enable (OE) places the output in the high-impedance state for multiple-unit sharing of a microcontroller input line.