“Designing an outdoor camera that can withstand a wide range of ambient temperatures from -30°C to +55°C presents two major design challenges. The first challenge is the ability to start at very high/low temperatures. The second challenge is the need to measure temperature accurately over a wide temperature range, since fans or heaters installed inside the camera operate based on temperature measurements. Accurate temperature results maximize the camera’s operating temperature range and prevent equipment failure.
Outdoor cameras play an important role in security applications, so you need to make sure they don’t malfunction or malfunction, whether you’re in the tropics, cold climates, or climates with extreme daily temperature differences.
Legacy outdoor cameras can only operate reliably within a certain temperature range. When the temperature is low, the internal resistance of the lithium battery is large, which makes the battery capacity rapidly degrade or even fail. At very high temperatures, a camera’s image sensor can produce “hot pixels,” which are bright individual pixels that adversely affect overall image quality.
Designing an outdoor camera that can withstand a wide range of ambient temperatures from -30°C to +55°C presents two major design challenges. The first challenge is the ability to start at very high/low temperatures. The second challenge is the need to measure temperature accurately over a wide temperature range, since fans or heaters installed inside the camera operate based on temperature measurements. Accurate temperature results maximize the camera’s operating temperature range and prevent equipment failure.
Designs with temperature switches can help address both of these challenges.
Learn more about the TMP390 temperature switch → Driving Industrial Innovation with Small Sensors
How fans and heaters work efficiently
Outdoor cameras, especially high-definition cameras, generate higher energy. When the ambient temperature is high, the fan can reduce the internal temperature to keep the camera functioning properly. In extreme cold conditions, although the camera generates a lot of heat, it is not enough to operate above the minimum operating temperature. Therefore, when the ambient temperature is low, a heater can be used to raise the internal temperature.
Figure 1 shows a traditional thermal protection design, where the microcontroller (MCU) or processor starts first and detects the temperature with the help of sensors. However, if the temperature is too low or too high, it may damage the MCU or image sensor when trying to boot. To avoid this, outdoor camera designs should return the camera to its minimum operating temperature before attempting to start the camera.
Figure 1: Traditional thermal protection design
The TMP390 dual-channel temperature switch provides independent over and under temperature detection without the use of an MCU. Since the temperature switch directly controls the fan and heater, it provides the proper temperature for the entire system before the MCU starts up, preventing the MCU from running at extremely high or low temperatures. Resistor-programmable temperature trip points provide flexibility for a variety of applications, while resistor-programmed thermal hysteresis options of 5°C or 10°C prevent unwanted digital output switching.
During startup at very low temperatures (see Figure 2), after power is applied, the temperature switch will start first; the MCU or other components remain off. Active low when the temperature is outside a safe range, at the same time, the heater and fan begin to increase the internal temperature. When the temperature reaches the preset value, the whole system starts to start. Compared with the traditional temperature protection design in Figure 1, the TMP390 temperature switch can regulate the temperature before the system starts, thus solving the challenge of starting at extremely low or extremely high temperatures.
Figure 2: Example circuit for TMP390 with 10°C hysteresis at +60°C and -40°C thresholds
The TMP390 temperature switch has 3C accuracy from -55°C to +130°C (±1.5°C from 0°C to +70°C), which provides sufficient accuracy over a wide temperature range. With accurate temperature measurement, outdoor cameras no longer have to leave room for temperature protection, maximizing the operating temperature range and effectively protecting the equipment within the system. Since the TMP390 temperature switch can precisely control the fan or heater, unnecessary power consumption in outdoor cameras is eliminated.
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