【Smart Kitchen】Environmental Sensor Schematic Design

太阳上的骑士

【Smart Kitchen】Environmental Sensor Schematic Design [Copy link]

 

The smart kitchen uses two environmental sensors, one is SHT45, which is used to detect the temperature and humidity of the environment, and the other is ADPD188BI, which is used to detect the smoke concentration.

1. SHT45

SHT45 is built on a new optimized CMOSens chip with low power consumption and high accuracy specifications, and a supply voltage range of 1.08 V to 3.6 V, making it ideal for mobile and battery-driven applications. Typical accuracy can reach ΔRH = ±1% RH and ΔT = ± 0.1°C.

Communicate with the host through IIC, there are three communication modes, namely standard mode, fast mode, and fast mode plus

Typical application circuit:

2. ADPD188BI

The ADPD188BI integrated optical module is a complete optical system for smoke detection using optical dual-wavelength technology. The module integrates an efficient optical front end, two light-emitting diodes (LEDs), and two photodiodes (PDs). The module uses a custom package that prevents the light from the LED from directly irradiating the photodiode before entering the smoke detection cavity.

The front end of the application-specific integrated circuit (ASIC) includes a control block, a 14-bit analog-to-digital converter (ADC) with a 20-bit burst accumulator, and three flexible, individually configurable LED drivers. The control circuit includes flexible LED signal transmission and synchronous detection. The analog front end (AFE) has best-in-class signal offset and corruption suppression. Signal offset and corruption are usually caused by modulated interference caused by ambient light. Data output and function configuration are realized on a 1.8V I2C interface or a serial peripheral interface (SPI) port.

Typical application circuit, I2C communication mode:

SPI communication mode:

3. Schematic Design

The schematic diagram consists of 6 parts.

1. Power supply part: responsible for system power supply, mainly composed of two LDOs.
2. Smoke sensor cavity: covers the smoke sensor to reduce the impact of ambient light on the detection results of the smoke sensor.
3. Interface: used for external connection. In order to make the interface as small as possible, both sensors use I2C communication.
4. Temperature and humidity sensor: Temperature and humidity sensor circuit.
5. Level conversion: Because the digital part of ADPD188BI is 1.8V voltage domain, and the STM32 development board is 3.3V, a level conversion is required. Because I2C communication is used, it is most appropriate to choose a 2-bit bidirectional voltage level converter suitable for open-drain and push-pull applications. Finally, TI's TXS0102 was selected, and the package is as small as 1 x 1.4mm, which is very suitable.
6. Smoke sensor: Use I2C communication.

wangerxian

This sensor is mainly used in smoke alarm equipment, right?

太阳上的骑士

wangerxian posted on 2022-8-11 09:48 This sensor is mainly used in smoke alarm equipment, right?

Yes, the essence of this is the scattering of light by smoke. Kitchen fumes will also scatter light. Just recalibrate it. But the problem is that the fumes will adhere to the surface of the sensor and pollute the sensor.

wangerxian

The Knight of the Sun published on 2022-8-11 16:59 Yes, the essence of this is the scattering of light by smoke. Kitchen fumes will also scatter light. Just recalibrate it. But the fumes will adhere to the transmission...

If there is too much smoke when cooking, could it cause misidentification?

太阳上的骑士

wangerxian posted on 2022-8-11 17:11 If there is too much smoke when cooking, is it possible to cause misidentification?

It is necessary to calibrate the relationship between the size of oil smoke and the size of the signal, so as to estimate the concentration of oil smoke, and then adjust the power of the range hood to reduce the harm of oil smoke to the human body.