Wireless smoke alarm all-round design and large delivery: master + wireless + sensing...

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Major fire incidents have occurred, causing significant damage to both human lives and property. As a result, automatic fire protection systems have gained widespread attention from the government, the public, and various industries. The demand for more advanced automatic fire alarm and suppression systems has increased significantly, driving continuous innovation in this field.

This article presents a comprehensive solution for an automatic fire alarm and suppression system. Below is the system diagram:

The image above illustrates the fire alarm and automatic fire extinguishing system provided by Shiqiang. This system uses flue gas sensors and temperature sensors combined with a microelectronic judgment circuit to trigger alarms or activate electromagnetic relays for early warning. Shiqiang’s SI7055 temperature sensor plays a key role in supporting the system. The collected data is sent to Renesas MCU R5F117BCGFP, which then transmits the signal via Silicon Labs’ SI4438 wireless transceiver chip to the main control unit through a CAN bus. The main control unit processes the information and controls the water spray mechanism, while also providing an alarm display function. For optimal performance, the wireless system must support strong wall penetration, with a high link budget and receiving sensitivity better than -110dBm. Common low-frequency bands like 315MHz, 433MHz, 868MHz, and 915MHz are typically used for wireless smoke detection.

Several key components from Shiqiang agent are used in this system. Here's an overview of their features and benefits:

Renesas MCU R5F117BCGFP:

The R5F117BCGFP integrates a wide range of analog functions, including operational amplifiers, comparators, and ADCs. It supports up to four op-amps and offers fast operation with a waiting time of only 13µs in high-speed mode, making it ideal for general analog signal processing. Its design allows for simple external components like resistors and capacitors, reducing the overall system size. Additionally, it includes a 12-bit ADC with up to 17 channels, and operates on a wide voltage range (1.6V to 3.6V), enabling power efficiency. With four operating modes—Operating, Halt, Stop, and Snooze—it can achieve ultra-low power consumption, down to 2µA in Halt mode at 15kHz. This makes it highly suitable for industrial control applications where power efficiency is critical.

The chip also features 32KB of code storage, 2KB of data memory, 3KB of RAM, and 42 I/O ports. It supports a wide operating temperature range (-40°C to +105°C) and includes an on-chip voltage monitor that provides real-time monitoring and alerts for abnormal power conditions, ensuring system reliability and safety, especially in battery-powered devices.

SiliconLabs EFM32WG230F256:

The EFM32WG230F256, available through Shiqiang, is a high-performance 32-bit Cortex-M4-based microcontroller with a maximum clock speed of 48MHz. It supports floating-point operations and offers flexible memory configurations, including 256KB/128KB/64KB of flash and 32KB of RAM. It features 56 I/O ports, 12 DMA channels, and 12 PRS channels for peripheral communication. The chip also includes hardware AES encryption and a backup RTC that can switch to an external battery during power loss. With multiple power-saving modes, it consumes as little as 20nA in shutdown mode, making it ideal for low-power applications.

Wireless Transceiver Chip Si44xx:

In the fire alarm system, two versions of the Si44xx series are available: Si4463 and Si4438. While Si4438 operates in the 425–525MHz range, Si4463 covers broader bands such as 315MHz, 868MHz, and 915MHz. When operating at 169MHz with a 500bps rate, Si4463 achieves a receiving sensitivity of -129dBm and a transmit power of 20dBm, offering excellent link budget performance. Its sleep current is as low as 30nA, and standby current is just 40nA. Combined with Epson’s high-performance 30MHz crystal, Ricoh’s R1172 power IC, and the UPG2214 RF switch, it forms a complete wireless module suitable for reliable long-range communication in fire detection systems.

Temperature Sensor SI7055:

The SI7055 from SiliconLabs is a cost-effective digital temperature sensor known for its high accuracy, low power consumption, and compact design. It maintains ±0.5°C accuracy over a wide operating range (-40°C to +125°C) and supports a voltage range of 1.9V to 3.6V. At 1Hz sampling frequency, it consumes only 195nA, and offers 14-bit resolution for precise measurements. Each unit is factory-calibrated and comes in a 3x3mm DFN package, making it ideal for space-constrained applications. It also meets AEC-Q100 automotive-grade standards, ensuring reliability in harsh environments.