Circuit Note CN-0537 Devices Connected/Referenced Integrated Optical Module for ADPD188BI Smoke Detection Circuits from the Lab reference designs are engineered and tested for quick and easy system integration to help solve todays analog, Ultralow Noise, 200 mA, ADP151 mixed-signal, and RF design challenges. For more information CMOS Linear Regulator and/or support, visit www.analog.com/CN0537. Ultralow Power Boost LT8410 Converter with Output Disconnect Multistandard Verified Smoke Detector Solution such as EN 14604, EN 54, and ISO 7240 will likely add similar EVALUATION AND DESIGN SUPPORT tests to address this and other concerns in the future, making Circuit Evaluation Boards it more important to have more advanced sensing capabilities. CN-0537 Reference Design Board (EVAL-CN0537-ARDZ) ADICUP3029 Arduino Form Factor Development Board The goal of these updated standards is to increase safety and (EVAL-ADICUP3029) decrease the number of fire related deaths by reducing the Design and Integration Files number of false alarms that are generated from everyday Schematics, Layout Files, Bill of Materials activity. For example, in addition to the traditional fire and smoke sensitivity tests, the 8th edition of UL 217 and the 7th CIRCUIT FUNCTION AND BENEFITS edition of UL 268 now requires that smoke detectors do not Since the 1970s, smoke detectors have become commonplace produce a false alarm during nuisance events, like cooking. in commercial and residential buildings. Two basic types of Therefore, modern smoke detectors must be able to detectors exist today, the ionization type that uses radioactive distinguish between a cooking nuisance event and a fire matter to ionize the air and checks for an electrical imbalance, event. Traditionally, this goal required a complicated solution and the photoelectric type that uses a light source aimed at an with multiple sensor technologies and a level of artificial angle away from a photodetector and checks for photodetector intelligence. However, the use of the ADPD188BI makes this current caused by the light reflecting from airborne particles solution significantly more simple to implement. to the photodiode. Although a combination solution of both The circuit shown in Figure 1 is a tested and verified smoke types is recommended, the photoelectric smoke detector is more detector reference design with an available algorithm and a popular due to its improved reliability in detecting common data set based on the ADPD188BI optical module. For easy house fires and faster response times to smoldering fires. and rapid development, the design is made compatible with Unfortunately, smoke detector technology and regulations the Arduino form factor controller platforms. Software and have also remained virtually the same since the 1970s despite embedded algorithms combined with the hardware can be the advances in electronics and common household materials used to evaluate smoke and fire tests specified in 8th edition through the decades. New revisions in standards, such as of the UL 217 and the 7th edition of the UL 268 standards. ANSI/UL 217 and ANSI/UL 268, published by Underwriters Verified algorithms are available for direct use to help deploy Laboratory (UL), or the NFPA 72 National Fire Alarm Code, the smoke detection solution faster, and additional data can published by the National Fire Protection Agency (NFPA), aim also be collected and added into the algorithm to adapt it for to address this gap by placing more complex requirements on other standards. modern smoke detector designs. Other worldwide standards, Rev. A Circuits from the Lab reference designs from Analog Devices have been designed and built by Analog Devices engineers. Standard engineering practices have been employed in the design and construction of each circuit, and their function and performance have been tested and verified in a lab environment at room temperature. However, you are solely responsible for testing One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. the circuit and determining its suitability and applicability for your use and application. Tel: 781.329.4700 www.analog.com Accordingly, in no event shall Analog Devices be liable for direct, indirect, special, incidental, Fax: 781.461.3113 20202021 Analog Devices, Inc. All rights consequential or punitive damages due to any cause whatsoever connected to the use of any reserved. Circuits from the Lab circuits. (Continued on last page) CN-0537 Circuit Note OPTIONAL BOOST +3.3V +3.3V REGULATOR +5V TO +6V LT8410 +5V VDD VDD TEMPERATURE AND MICRO-SD CARD HUMIDITY +1.8V ADP151-1.8 +3.3V SENSOR TEMPERATURE AND BLUE/IR DATA HUMIDITY DATA VDD1 VDD2 VLED3 VLED1 ADPD188BI SPI INTERFACE INTEGRATED OPTICAL MODULE FOR SMOKE DETECTION BLUE/IR ADICUP3029 WITH DATA 2 SMOKE AND FIRE I C INTERFACE DETECTION ALGORITHM PDC PDET1 ENABLE VIA GPIO SCATTERED BLUE/IR LIGHT PDET2 HEATING RESISTORS ALARM INDICATORS +5V +5V +5V BUZZER ALARM LED VLED1 SMOKE CHAMBER VLED3 LED EN IR BLUE EMITTED BLUE/IR LIGHT HEATER EN BUZZER EN TEST BUTTON NOT REQUIRED FOR THE REGULATIONS Figure 1. CN-0537 Block Diagram Two integrated photodetectors then receive the scattered light CIRCUIT DESCRIPTION and produce proportional levels of output current, which are Smoke Detection Using the ADPD188BI converted internally by the AFE into digital code. Assuming the The ADPD188BI optical module is a complete photometric LED optical power is kept constant, an increase in ADPD188BI system specifically designed for smoke detection applications. output values over time indicates an increase or buildup in Using the ADPD188BI in place of traditional, discrete smoke airborne particles. detector circuits greatly simplifies the design as the opto- UL 217 and UL 268 Smoke and Fire Test Algorithm electronics (consisting of two LEDs and two photodetectors) and the analog front end (AFE) are already integrated into The UL 217 and UL 268 standards require detectors to respond the package. to different types of fire and smoke within a specific window of time and obscuration. Table 1 lists the obscuration To perform smoke detection, the ADPD188BI utilizes a dual- percentage and response time requirements for each UL 217 wavelength technique: two integrated LEDs emit light at two and UL 268 test. different wavelengths and one LED at 470 nm (blue light) and the other LED at 850 nm (infrared light). These LEDs are Table 1. Fire Conditions and Specifications pulsed in two independent time slots, and the transmitted light is Alarm scattered back onto the device by particulate matter in the air. Alarm Time Obscuration 1 1 Fire Condition Specification Specification Wood Fire <4 minutes N/A Paper Fire <4 minutes N/A Polyurethane Fire <4 minutes <5 % per foot Smoldering N/A <12 % per foot Polyurethane Fire Smoldering Wood N/A <10 % per foot Hamburger Nuisance N/A Not before Test <1.5% per foot 1 N/A means not applicable. LIGHT SOURCE (L) RECEIVER INCLUDING DETECTOR (S) For the CN-0537 reference design, these specifications are Figure 2. Backscattering of Light from ADPD188BI LEDs met by analyzing the blue and infrared (IR) output data of the ADPD188BI through a smoke detection algorithm. Rev. A Page 2 of 8 22281-003 22281-001