S3F8S28. Smoke Detector. Revision 0.00 February Samsung Electronics Co., Ltd. All rights reserved.

Transcription

1 S3F8S28 Smoke Detector Revision 0.00 February 2011 Application Note 2011 Samsung Electronics Co., Ltd. All rights reserved.

2 Important Notice The information in this publication has been carefully checked and is believed to be entirely accurate at the time of publication. Samsung assumes no responsibility, however, for possible errors or omissions, or for any consequences resulting from the use of the information contained herein. Samsung reserves the right to make changes in its products or product specifications with the intent to improve function or design at any time and without notice and is not required to update this documentation to reflect such changes. This publication does not convey to a purchaser of semiconductor devices described herein any license under the patent rights of Samsung or others. Samsung makes no warranty, representation, or guarantee regarding the suitability of its products for any particular purpose, nor does Samsung assume any liability arising out of the application or use of any product or circuit and specifically disclaims any and all liability, including without limitation any consequential or incidental damages. "Typical" parameters can and do vary in different applications. All operating parameters, including "Typicals" must be validated for each customer application by the customer's technical experts. Samsung products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, for other applications intended to support or sustain life, or for any other application in which the failure of the Samsung product could create a situation where personal injury or death may occur. Should the Buyer purchase or use a Samsung product for any such unintended or unauthorized application, the Buyer shall indemnify and hold Samsung and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, expenses, and reasonable attorney fees arising out of, either directly or indirectly, any claim of personal injury or death that may be associated with such unintended or unauthorized use, even if such claim alleges that Samsung was negligent regarding the design or manufacture of said product. Copyright 2011 Samsung Electronics Co., Ltd. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electric or mechanical, by photocopying, recording, or otherwise, without the prior written consent of Samsung Electronics. Samsung Electronics Co., Ltd. San #24 Nongseo-Dong, Giheung-Gu Yongin-City, Gyeonggi-Do, Korea Contact Us: yongbum.k@samsung.com TEL: (82)-(31) FAX: (82)-(31) Home Page:

3 Revision History Revision No. Date Description Author(s) , Initial Li Baoke

4 Table of Contents 1 OVERVIEW Features: WORKING MECHANISM Smoke Detector Types How Photoelectric Smoke Detector Works Typical System Layout HARDWARE IMPLEMENTATION S3F8S28 Features System Block Diagram & Specification Block Diagram System Specification Operating Conditions: Functions Power Consumption Hardware Implementation Hardware Block Diagram Hardware Circuit Power Circuit: Signal Separator: Pulse Width: Working Condition Indicator: Infrared Transmitter: Infrared Receiving: PGM Interface: SOFTWARE IMPLEMENTATION Source Code Files Software Flow Chart Main Task Command Receive Flow Data Uploading Flowchart Smoke Checking Flow Working Condition Indicating SMOKE DETECTOR DEMO SYSTEM Demo System System Test Test Environment Test Sequence Test Results Functions Power Consumption

5 6 APPENDIX S3F8S28 Features Memory General I/O bit High-speed PWM Timer/Counters A/D Converter Serial Interface Oscillation Frequency Operating Temperature Range Operating Voltage Range Package Types Schematic Source Code

6 List of Figures Figure Title Page Number Number Figure 2-1 Smoke Detector Figure 2-2 Light Scattering Detector Figure 2-3 Light Scattering Detector with Smoke Figure wrie Detector Circuit Figure 3-1 Smoke Detector System Block Diagram Figure 3-2 Hardware Block Diagram Figure 3-3 Power Circuitry Figure 3-4 Signal Separator Figure 3-5 Pulse Width Figure 3-6 Working Condition Indicator Figure 3-7 Infrared Transmitter Figure 3-8 Infrared Receiving Figure 3-9 PGM Interface Figure 4-1 Software Flowchart Figure 4-2 Command Receive Flowchart Figure 4-3 Host Signal Figure 4-4 Data Uploading Flowchart Figure 4-5 Detector Signal Figure 4-6 Send Signal Processing Figure 4-7 Smoke Signal Checking Flow (ADC Sample & Convert) Figure 4-8 Working Condition Indication Flow Figure 5-1 Working Condition Indication Flow Figure 6-1 Schematic

7 List of Tables Table Title Page Number Number Table 3-1 Signal Separator Output Table 4-1 Source Code Files Table 4-3 Signal Separator Output Table 5-1 Power Consumption Normalized For One Second

8 1 Overview If we can reliably monitor the smoke density for a working site, we can prevent and minimize the damage of fire accidents and thus reduce the cost of property damage and loss of human life. So the smoke detector is widely used in many buildings and homes to alarm at the beginning stage of a developing fire accident. This smoke detector reference design describes how to implement an ultra-low-power photo-diode-based smoke detector. An infrared (IR) diode and IR receiver are used inside a smoke chamber to detect the presence of smoke. The IR diode is pulsed periodically, and the IR receiver signal is examined to determine if smoke is present in the chamber. An operational amplifier is used to magnify the IR receiver current as a trans-impedance amplifier, so it can be sampled by the ADC in the MCU. This smoke detector reference design used Samsung highly integrated low cost 8-bit microcontroller S3F8S28, which is ideal for smoke detector with ultra low power consumption (less than 200uA run current at 3.0V, 455kHz), timer, PWM, 12-bit ADC and full flash ROM for realizing EEPROM function. 1.1 Features: Low Power Consumption: total system current consumption less than 200uA Combined with temperature sensor, can detect different fire accident. High precision specific amplifier for reliable smoke signal detect Auto generate address code by software with self-adaptive. Self-checking function, control can monitor detector's working status. 1-1

9 2 Working Mechanism 2.1 Smoke Detector Types Two basic types of smoke detectors are used today: ionization and photoelectric. The sensing chambers of these detectors use different principles of operation to sense the visible or invisible particles of combustion given off in developing fires. The characteristics of an ionization detector make it more suitable for detection of fast flaming fires that are characterized by combustion particles in the 0.01 to 0.4 micron size range. Photoelectric smoke detectors are better suited to detect slow smoldering fires that are characterized by particulates in the 0.4 to 10.0 micron range. Each type of detector can detect both types of fires, but their respective response times will vary, depending on the type of fire. Ionization detectors are prone to malfunction when used in noisy, dusty, or damp environments and, thus, are subject to frequent maintenance. Ionization detectors also produce radiation pollution. Therefore, the popularity of ionization detectors has been on decline while photoelectric detectors are increasing in popularity. Figure 2-1 Smoke Detector According to the application fields and power supply modes, the smoke detector can be divided into two categories: Home applied smoke detector and building applied smoke detector. Home applied smoke detector is powered by 9V battery that is separated individually. This type smoke detector works in sleep mode in most time, and wake up every 8 seconds to check the smoke status, if the smoke is detected, the buzzer is sounded. Building applied smoke detector is powered by 24V distribution line, and communicates with the control unit of the fire alarm system control unit. Each smoke detector acts as a monitor point. When any of the smoke detector raise alarm signal, it will send message to the control unit, and the control unit will notice all the smoke detectors to sound. 2-1

10 2.2 How Photoelectric Smoke Detector Works Smoke produced by a fire affects the intensity of a light beam passing through air. The smoke can block or obscure the beam. It can also cause the light to scatter due to reflection off the smoke particles. Photoelectric smoke detectors are designed to sense smoke by utilizing these effects of smoke on light. Most photoelectric smoke detectors are of the spot type and operate on the light scattering principle. A lightemitting diode (LED) is beamed into an area not normally seen by A photosensitive element, generally a photodiode. (Figure 2-2) When smoke particles enter the light path, light strikes the particles (Figure 2-3) and is reflected onto the photosensitive device causing the detector to respond. Figure 2-2 Light Scattering Detector Figure 2-3 Light Scattering Detector with Smoke 2-2

11 2.3 Typical System Layout Smoke detectors are generally categorized as either 2-wire or 4-wire detectors. Two-wire detectors derive their power from their connection to the fire alarm control panel alarm initiating device circuit. Since they are dependent on the initiating circuit, these 2-wire detectors must be tested and listed for compatibility with the associated control panel, to ensure proper operation. Four-wire detectors are powered from a separate pair of wires, and, like the 2-wire detector, apply an electrical short across the associated alarm initiating device circuit to transmit an alarm. Figure 2-4 shows a type of 2-wire detectors system circuit. Supervision of this circuit is accomplished by passing a low current through the installation wiring and an end-of-line resistor. The fire alarm control panel monitors the increases or decreases in the supervisory current and sends an alarm or trouble condition, respectively. A single open in a Class B circuit disables all devices electrically beyond the open. Figure wrie Detector Circuit 2-3

12 3 Hardware Implementation 3.1 S3F8S28 Features This reference design is using Samsung S3F8S28 as main microcontroller. S3F8S28 is a 24-pin microcontroller, with 8-K bytes flash ROM, and 272 Bytes RAM. It has a 8-bit timer, a 16-bit timer, 12-bit resolution ADC with 13 channels, and two channel 8-bit/12-bit/14-bit PWM. These all features makes S3F8S28 is very suitable for smoke detector application: 12-bit ADC for smoke detector signal measuring; Less than 150uA run current with 455KHz ceramic OSC is dedicated for low power consumption of smoke detector application. 3-1

13 3.2 System Block Diagram & Specification Block Diagram Figure 3-1 Smoke Detector System Block Diagram As show in Figure 3-1, an infrared (IR) diode and IR receiver are used inside a smoke chamber to detect the presence of smoke. The IR diode is pulsed periodically, and the IR receiver signal is examined to determine if smoke is present in the chamber. An operational amplifier is used to magnify the IR receiver current. So it can be sampled by the ADC module in the MCU. For power saving, between sampling periods, the operational amplifier and IR circuitry are shut down, and the microcontroller is in a sleep mode for consuming less current. The smoke detector samples the IR circuitry for the presence of smoke. When smoke is detected, the buzzer is sounded. In the smoke detection industry, many domestic and foreign companies use the System Sensor 2-wire bus. The bus 24V is used to generate 10V for the detector and 3.3V for the MCU. The detector transmits the related data to the main units by a constant current pulse. The main unit receives the detector data samples and communicates with these detectors via a polling mechanism. Then the main unit processes this data and raises the alarm. 3-2

14 3.2.2 System Specification Operating Conditions: Operating Voltage: 24V DC (Range: 18 to 27V) Operating Temperature: 10 C to + 50 C Functions Sensitivity is settable: Level I: 0.23dB/m Level II: 0.38dB/m Level III: 0.55dB/m Electronic address code, auto-assigned by software. Communication: Communicate with central control unit by 2-wire bus. If smoke is detected, signal the control unit in 3 seconds. Reliable detecting methods for minimize the impact of an unwanted signal Working condition indication with Red/Green LED. Audio Alarm when smoke is detected Power Consumption MCU run current: less than 200uA (total system). Smoke checking current: 4mA (include ADC convert and IRLED current) Average current: less than 300uA. 3-3

15 3.3 Hardware Implementation Hardware Block Diagram Buzzer Power Control PGM Interface Amplifier Analog Signal to ADC Working Condition Indicator Infra Red Receiver Pulse Width Infra Red Transmitter Transmitter Control Signal Separator 3.3V Power Circuit 24V 2-Wire Bus Figure 3-2 Hardware Block Diagram 3-4

16 3.3.2 Hardware Circuit Power Circuit: Power is supplied from the System Sensor bus main circuit supply power. The MCU 3.3V supply is generated via an LDO. Figure 3-3 Power Circuitry As shown in Figure 3-3, resistor R19 and Z1 form a constant voltage series circuit. The 24V from the System Sensor main circuit is used to produce an 11V stable voltage. The circuit transistor Q4 current amplifier, diode D6, D8 isolation, capacitor C7, and C8 filters this to produce two rails of stable 10V voltage. One of the 10V rails will be used as VDD to supply the infrared transmitter, the LED display, the BUZZER power, and the signal control circuitry power. The other 10V rail is passed to low power consumption, LDO HT7133, to produce a stable 3.3V voltage Vcc to supply the signal separator circuitry and MCU S3F8S

17 Signal Separator: This block separates the power and signal voltages and sends the system data to the MCU. As shown in Figure 8, resistor R15, R23, R22,R24, Zener diode Z2 (11V), capacitor C9, and transistor Q5 form a splitter circuit by which the System Sensor s 24V and non-24v signal levels are separated. 24V signals output logic "0" and non-24v signals output logic "1". Resistors R21, R25, R26, R16, diode D3, capacitor C10, and transistor Q6, form a 0V signal two value separator circuitry. The System Sensor bus can have three voltage levels: 24V, 5V, and 0V. The circuit in Figure 8 isolates these voltages, as shown in the table below: Figure 3-4 Signal Separator Table 3-1 Signal Separator Output Bus Voltage 24V Isolation Output 0V Isolation Output 24V 0 0 5V 1 0 0V

18 Pulse Width: This block will receive pulse width cycles, convert the signal to a constant current pulse width, send it through the System Sensor, and then send it back to the main controller. As shown in Figure 3-5, transistors Q2, resistors R12, R13, and OP-AMP U3A form a simple constant current circuit. When "CRTLPSG" is in the high state, the System Sensor main circuit will produce a 20mA constant current pulse signal. By measuring the current pulse width, the return value data can be determined. Figure 3-5 Pulse Width 3-7

19 Working Condition Indicator: This block is used to indicate the working condition and status of the smoke detector. In normal conditions, the indicator will blink every 8 seconds. During a fire alarm, it will blink frequently. Figure 3-6 Working Condition Indicator 3-8

20 Infrared Transmitter: This block sends the infrared pulse signals. As shown in Figure 3-7, the infrared pulse transmitter circuit consists of the resistor R1, R2, R3, transistor Q1, and emitting diode. The S3F8S28 can control and generate a few nanoseconds of an infrared pulse signal. Figure 3-7 Infrared Transmitter 3-9

21 Infrared Receiving: This block receives the infrared signals reflected by the smoke. It then converts the light signals to a pulse signal as show in Figure 3-8. Figure 3-8 Infrared Receiving 3-10

22 PGM Interface: This block is used for MCU software download & update. Figure 3-9 PGM Interface 3-11

23 4 Software Implementation This section describes the software used in the boiler controller system reference design. The software is written in C language. 4.1 Source Code Files Table 4-1 lists the source code and its included files. Table 4-1 Source Code Files File Name Description Note ios3f8s28.h Declaration of S3F8S28 registers and interrupt vectors Global_define.h Declaration of global variables and global defines Main.c Configuration of peripherals, interrupt service routine, and main task Op_Com.c Operation functions and communication functions Op_Com.h Head file of Op_Com.c, function and variable declaration Sample.c ADC sampling functions Sample.h Head file of Sample.c, function and variable declaration 4-1

24 4.2 Software Flow Chart This smoke detector application note is dedicated for distributed detector networks that using Host-Terminator mode. The host sends command to detector, and detector feedback smoke status to host. Normally, there are more than one hounded detectors in the network, all the detectors are connected on one 24V bus, the 24V bus also supply power to every detectors, and the command signal are also transmitted by the 24V bus by combine define voltage level on the bus Main Task So the main flow chart of the detector is receiving the command from the host, and operates according to the command, then feedback the smoke status to host. Start System init Get parameter from host N Received Command? Send sample result to host Y N N Command = 1? Y Smoke detected? Y Check again Smoke detected? Y Send Alarm Signal to host N Command = 2? Y Send sample result to host N Command = 3? Y Alarm N Command = 4? Store parameters Figure 4-1 Software Flowchart 4-2

25 4.2.2 Command Receive Flow Figure 4-2 Command Receive Flowchart The communication between the smoke detector and the control unit are composed by two methods: for upward from smoke detector to control unit, using 4-20mA constant current loop; for downward from control unit to smoke detector: using 24V (physical '0')/5V (physical '1') voltage signal on the 24V bus line. The 5V voltage on the bus represent physical '1', and the 24V (normal state) represent physical '0'. And the logic '1' is represented by a long duration of physical '1' in a fixed period (about 4ms), the logic '0' is represented by a short duration of physical '1' in a fixed period. 4-3

26 Figure 4-3 Host Signal The signal's transmission is captured by the interrupt of Timer 1, and in the capture interrupts service routine, by checking the physical level and lasting duration, can get the signal's logic value. The host send 16-bit length data with 2-bit checking bits, the first 8-bit is the address value, the last 8-bit is the data, and the start signal is a physical '0' lasting for 5ms. And the checking bits are also stop bits. The host also send broadcast signal to detectors. The detector receive or feedback to host according to different command. When detector received the address signal, it compare the address value with it's own address, if matched, then it will continue to receive the command, if not, it will stop and abandon received data. The command set has four commands in this application note. The first command is used to let detector start to check the smoke status and feedback the sampling result to host. This command is the most frequently used command; The second command is broad cast command, the host send command to all detectors on the network, and when the detector received the command, if it has no updated sample result, it need send the sample result to host; the third command is alarm signal, if host received alarm from one detector, it will note all the detector on the bus to signal alarm, so this command is used. When detector received this command, it will start to alarm. Table 4-2 Signal Separator Output No. Command Contents 1 1 Check smoke status and feed back 2 2 Broadcast 3 3 Alarm 4 4 Setting address 4-4

27 4.2.3 Data Uploading Flowchart Figure 4-4 Data Uploading Flowchart The current signals are represented by the current on/off, on (20mA current) represents '1', off(4ma current) represents '0'. If there is current on the line, that represent 'high', if there is no current on the line, that represent '0'. And different current last time represent different logic signal, as show in below figure: 4-5

28 Figure 4-5 Detector Signal The pulse width is about 200us, and the baud rate is about 5Kbps. When the detector received matched address, it will operate according to the command type. Then it will upload the smoke sampling results and alarm status to host. The return data is 9-bit length, 8-bit data and 1-bit alarm signal. The detector must send the data to host in 5ms after received the command. The Time A is used to generate time interval for signal period. The sending process status switching is done in the interrupt service routine of Time a match interrupt, below figure shows the processing flow in interrupt. Figure 4-6 Send Signal Processing 4-6

29 4.2.4 Smoke Checking Flow Figure 4-7 Smoke Signal Checking Flow (ADC Sample & Convert) For power saving, the OP-AMP's power supplier is an I/O port of the MCU. When IrDA transmitter starts to emitting, the I/O port (P0.5) is set to high to provide power to OP_AMP. After the voltage stable, the ADC start to sample the OP_AMP output to check the smoke. The ADC will sample 8 times and take the average value as the convert result for get a reliable data. If the threshold condition was detected, MCU will check again to verify the ADC convert result. If the smoke signal is detected again, the detector will change work status to alarm, and will send alarm signal to host and start alarm meanwhile. 4-7

30 4.2.5 Working Condition Indicating Start If working status = 0 (system reset) Y Set LED Interval = Initial value BUZ off N If working status = 1 (Normal/no smoke) Y Set LED Interval = Normal value BUZ off N If working status = 2 (Smoke detected) Y Set LED Interval = Alarml value BUZ On N If working status = 3 (Alarm) Y Set LED Interval = Alarml value BUZ On N Y End N Figure 4-8 Working Condition Indication Flow The LED is used to indicate the working condition of the smoke detector, after reset, the LED will blink every 1s and last for several seconds. When the system is running in normal status that no smoke was detected, the detector working in normal state and LED will blink every 8s. When the smoke is detected, the detector will change state to alarm state and the LED will blink every 2s and the Buzzer will sound alarm. The host also will send alarm signal to detector, when detector received this command, it will change to alarm state, and start to alarm with LED blink every 2s and Buzzer sound alarm. 4-8

31 5 Smoke Detector Demo System 5.1 Demo System The demo system of the smoke detector is based on S3F8S28, and the system clock is 455kHz ceramic. That's the new developed clock module dedicated for smoke detector application with low power consumption in running mode. Figure 5-1 shows the demo system. MCU 455KHz Ceramic OSC OP-AMP Smoke Chamber SPGM POWER Figure 5-1 Working Condition Indication Flow 5-1

32 5.2 System Test Test Environment Power supplier: 24VDC Operating Temperature: 25 C System Clock: 455kHz MCU VDD voltage: 3.3V Test Sequence At the beginning of the test process, the smoke chamber is sealed, the IrDA receiver cannot receive the Infrared signal, and the smoke detector worked in normal state; After a while, open the seal to make the receiver can receive the infrared signal that's similar with the smoke is exist (smoke reflect the infrared signal to receiver, so this can simulate the smoke condition). The ADC converter will get a abnormal value, then the detector will check the smoke is detected or not. When the smoke existing is confirmed, the detector will send alarm to host and sound alarm signal, the LED will blink quickly. If we seal the smoke chamber again, the receiver will receive the IrDA signal, the smoke will enter normal mode, it will stop alarm. In the demo system, there is not available host, so using software to simulate the host; the program will generate a command periodically to simulate the host's command. And the detector wills response according to the command. For uploading the data to host, the 20mA current loop signal is used. The data will be sent by detector after executing the command from host, for the reason of the host is not exist in this demo system, so the feedback of the host is not available, but all the communication module and protocol is realized in this reference design. 5-2

33 5.2.3 Test Results Functions Sensitivity is acceptable. Electronic address code auto-generated by software. Communicate with central control unit by 2-wire bus. If smoke is detected, signal the control unit in 3 seconds. Reliable detecting and minimizing the impact of an unwanted signal Working condition indication with Red/Green LED. Audio Alarm when smoke is detected Power Consumption MCU run current: 110uA (total system). Smoke checking current: 80uA (average current, include ADC convert and IRLED current) Average current: less than 200uA. Table 5-1 Power Consumption Normalized For One Second Function Duration Current Normalized Current System Run Continuous 109uA 109uA ADC 60us 1mA 0.06uA IR LED 100us 100mA 10uA Operational Amplifier 190us 650uA 0.12uA Communication current 3.0ms 20mA 60uA Condition indicating LED 2ms 10mA 20uA Total 199uA 5-3

34 6 Appendix 6.1 S3F8S28 Features The key features of S3F8S28 include: Memory 8-Kbyte internal multi-time program Flash memory 272-byte general-purpose register area General I/O Three I/O ports (Maximum 22 pins) Bit programmable ports bit High-speed PWM 12-bit PWM 2-channels Timer/Counters One 8-bit basic timer for watchdog function One 16-bit timer or two 8-bit timers A/B with time interval mode One 16-bit timer 1 with capture input A/D Converter Thirteen analog input pins (MAX) 12-bit conversion resolution 6-1

35 6.1.6 Serial Interface One channel UART One channel IIC Oscillation Frequency 0.1MHz to 1MHz external Low Gain crystal oscillator & MHz external High Gain crystal oscillator Internal RC OSC & On-chip 32kHz Ring Oscillator Operating Temperature Range 40 C to + 85 C Operating Voltage Range 2.0V to 5.5V (LVR disable) Package Types 24-SOP-375; 24-TSSOP-BD44; 20-DIP-300A; 20-SOP-375; 20-SSOP

36 6.2 Schematic Figure 6-1 Schematic 6-3

37 6.3 Source Code For more information about the source code, please refer to Src_Smoke Detector.rar. 6-4