Web Site: www.parallax.com Office: (916) 624-8333 Forums: forums.parallax.com Fax: (916) 624-8003 Sales: sales parallax.com Sales: (888) 512-1024 Technical: support parallax.com Tech Support: (888) 997-8267 Gas Sensor Board ( 27983) The Gas Sensor Board is designed to work in conjunction with one of the gas sensors listed below (not included) allowing you to determine when a preset gas level has been reached or exceeded. CO (Carbon Monoxide) Gas Sensor ( 605-00007) CH4 (Methane) Gas Sensor ( 605-00008) LPG (Propane) Gas Sensor ( 605-00009) C2H5OH (Alcohol) Gas Sensor ( 605-00011) The board can interface to a microcontroller, allowing the sensor to be controlled and monitored automatically. Interfacing with the Gas Sensor Board is done through a 4-pin SIP header and requires two I/O pins from the host microcontroller. The Gas Sensor Board is intended to provide a means of comparing gas sources and being able to set an alarm limit when the source becomes excessive. The Gas Sensor Board and individual gas sensors replace the discontinued product numbers listed below. Please note that on boards labeled 27983 pin 2 is active-high, and on boards labeled 27904, 27930, 27931, and 27932, pin 2 is active-low. 27983 + 605-00007 replaces 27931 CO Gas Sensor Module 27983 + 605-00008 replaces 27930 CH4 Gas Sensor Module 27983 + 605-00009 replaces 27932 LPG Gas Sensor Module 27983 + 605-00011 replaces 27904 C2H5OH Gas Sensor Module Parallax does not provide gas calibration data on these sensors and such data as well as the alarm settings are the responsibility of the user to define. For information on calibration please see page 3. Features Application Ideas Easy SIP header interface Gas level over-limit alarm Compatible with most microcontrollers Stand-alone/background sensing device Low-power standby mode Environmental monitoring equipment Key Specifications Other Items Required Power requirements: 5 VDC ~165 mA Tiny flat-head screwdriver (heater on) / ~60 mA (heater off) A source of gas for calibration Interface: 1 TTL compatible input Gas sensor (listed above) (HSW) 1 TTL compatible output (ALR) Operating temperature: 14 to 122 F (-10 to +50C) Dimensions: 1.50 x 1.0 x 1.0 in (38.1 x 25.4 x 25.4 mm) Copyright Parallax Inc. Gas Sensor Board ( 27983) v1.0 1/11/2013 Page 1 of 4 Precautions Be aware that the gasses detected by these gas sensors can be deadly in high concentrations. Automotive exhaust and charcoal cooking grill exhausts emit carbon monoxide (CO). Propane Gas (LPG) can leak from propane grills and furnaces and Methane (CH4) can be found in animal farming areas. Always be careful to perform gas tests in well- ventilated areas. THE GAS SENSOR BOARD IS NOT DESIGNED FOR OR APPROVED FOR ANY APPLICATION INVOLVING HEALTH OR HUMAN SAFETY. THE GAS SENSOR BOARD IS FOR EXPERIMENTAL PURPOSES ONLY. PARALLAX, INC. ABSOLVES ITSELF OF ALL LIABILITY AND RESPONSIBILITY ASSOCIATED WITH THE CUSTOMER S USE OF THE GAS SENSOR BOARD AND IS NOT RESPONSIBLE FOR ANY BODILY INJURY, DEATH OR PROPERTY DAMAGE AS A RESULT OF USING THE GAS SENSOR BOARD. Connecting and Testing The gas sensor canister plugs into the socket on the front of the board. The gas sensors are essentially resistive devices and are not polarized, so there is no need to be concerned about plugging it in backwards. It will work in either orientation. The 4-pin SIP header on the Gas Sensor Board makes it easy to connect to a breadboard or SIP socket. The four connections are defined in the table below. Connection to a 5V microcontroller, such as the BASIC Stamp module, would be pretty straight forward and require two I/O pins one input for detecting the alarm signal (ALR) and the other an output for controlling the internal heater (HSW). TM For a 3.3 V microcontroller such as the Propeller chip, a 3.9 k10 k resistor would be required from the ALR output to the Propeller chip input pin. Pin Definitions and Ratings Gas Sensor Board Pin Name Function Level E1 ALR Alarm output to host microcontroller 0V / 5V E2 HSW Heat switch input from microcontroller, active high 0V / High* E3 +5V +5 VDC power 5V E4 GND Ground, connects to common ground 0V TP1 Test Point 1+ Buffered output of sensors (voltage divider) 0V 5V TP2 Test Point 2- Ground, connects to common ground 0V TP3 Test Point 3+ Trip Level voltage set by potentiometer (R4) 0V 5V TP4 Test Point 4- Ground, connects to common ground 0V * The HSW can be activated from 3-5 VDC and has an internal 150 k pull-down resistor. NOTE: Sensors may rattle if shaken this is normal. Copyright Parallax Inc. Gas Sensor Board ( 27983) v1.0 1/11/2013 Page 2 of 4