Overview
Fires have long been one of the most common and severe hazards. Historically, wooden structures were prone to rapid collapse in fires, causing significant economic loss and casualties. Modern buildings are more fire resistant structurally, but high-rise layouts can trap occupants during a fire. With the development of IoT and related communication technologies, smart smoke detectors that monitor smoke signals in real time are being adopted more widely. Research shows that installing smoke alarms can increase the likelihood of residents escaping a fire to about 95%. In aging-friendly home retrofits, smoke detectors are an important measure to protect elderly residents.
Application
Smoke alarms are critical safety devices that detect elevated smoke concentration and issue timely alerts to allow occupants to take appropriate actions and prevent fire spread. They are typically installed on ceilings where rising smoke can be detected more easily.
Use Cases
Typical deployment environments include rented housing, residential complexes, factories, small shops, schools, warehouses, and office buildings.
Design Description
- Power: Powered by a 9V/2200mAh dry battery. An LDO regulator provides 3.3V. Battery level is monitored by an ADC.
- Status indicators: A red LED indicates battery voltage status. The red LED is off when the battery is full and lights when the battery is low; the buzzer emits a short beep about every 50 seconds during low-voltage condition. A green LED indicates smoke alarm status: it lights when an alarm condition is present and remains off otherwise.
- Alarm test: After power is applied the detector operates normally. The green indicator flashes approximately once every 40 seconds. Pressing the test button causes the buzzer to sound and the green alarm indicator to light; releasing the button returns the detector to normal operation. During self-test, the detector transmits a wireless signal (for wireless-networked detectors) so the security alarm host can identify the test.
- Smoke sensor: Detects smoke particles and flame.
- Communication: An NB module transmits smoke concentration data and alarm information in real time.
Key Features
- Long standby life, up to 3 years.
- Simple structure, no wiring required, easy installation, with automated monitoring.
MCU Features
| System | Item | Specification | Peripheral | Item | Specification |
|---|---|---|---|---|---|
| System configuration | CPU core | Enhanced 80C51 core | |||
| Max frequency | 16 MHz | ||||
| Timer | 3 general 16-bit timers; 2 advanced 16-bit timers supporting input capture/output compare/complementary PWM outputs; 1 low-power 16-bit timer supporting low-power timed wakeup | ||||
| WDT | 1 watchdog timer that can generate reset or interrupt signals | ||||
| Internal memory | Flash | 64 Kb | Peripheral interfaces | UART | 4 channels |
| SRAM | 8 Kb | SPI | 4 channels | ||
| Analog | ADC | 7 channels × 12-bit | IC | 2 channels | |
| Vref | 2.4 V | LP UART | 1 channel | ||
| PDR | Power-down reset | RTC | Low-power RTC | ||
| Comparator | 2 channels, wake-up capable | RNG | 1 random number generator | ||
| Low-power modes | Halt | 0.6 μA | Electrical | Operating voltage | 2.0 – 5.0 V |
| Active-halt | 0.85 μA | PVD | Programmable voltage detection | ||
| Low-speed run | 80 μA @ 32 kHz | CRC | CRC8 checksum | ||
| High-speed run | <4 mA @ 16 MHz | Operating temperature | -40 to +85 °C | ||
| Package | Three package options: TSSOP20, QFN32, LQFP48. Up to 42 GPIOs, all mappable to interrupt vectors. | ||||
