A gas heater is a heating device often used in a family room. It consumes oxygen when working. Under unventilated conditions, working for a long time will cause indoor oxygen deprivation, causing discomfort, even suffocation, and endangering personal safety. Oxygen protection design. The role of the hypoxia protection device is: when the device detects that the oxygen content of the indoor air is low, it will automatically close the control valve and alarm and display the hypoxia indicator to remind the user to ventilate. It is a very common temperature sensor, which is widely used in temperature measurement life. Its principle is: the two ends of two different conductors are connected into a closed loop. Due to the unequal temperature of the two ends, a thermoelectric potential is generated in the loop. This phenomenon is called thermoelectric phenomenon in physics. This article mainly uses the thermoelectric phenomenon to design a hypoxia protection device. 1. The working principle of the hypoxia protection device The working principle of this protection is: when the fuel gas supply and oxygen supply are constant, the flame combustion temperature is also constant. When the oxygen content in the air is sufficient, the flame temperature can reach 700℃ About; when the oxygen content in the air decreases, the flame temperature also decreases. According to American standards, the temperature of the flame in an oxygen-deficient state does not exceed 450°C, and the thermoelectric potential at a relative temperature of 450°C is 1815mV. If the temperature of the normal open flame measured by the thermocouple is not enough, it can be deemed that the oxygen content in the air is not enough, and the alarm needs to be alarmed and the control valve closed. The hypoxia protection function of this scheme is realized as follows: It adopts the wide-temperature single-chip AT89C2051, which has an internal analog comparator, and P110 and P111 are the input pins of the comparator. Connect the potential signal of 1815mV to the P111 pin. The voltage signal of the reference terminal is required to be stable, so connect a voltage stabilizing device at VCC. The flame temperature signal measured by the thermocouple is amplified and then connected to the P110 pin, and then the internal analog comparator is used to compare the two electrical signals. If the P110 pin signal is lower than the P111 pin signal, it means that the room is lack of oxygen. At this time, the control valve is closed and an alarm is displayed.　　Second, hardware composition　　The device is mainly composed of a single chip microcomputer, a thermocouple, and a potentiometer. The single-chip microcomputer adopts the high-efficiency single-chip AT89C2051 introduced by the American ATMEL company, which has its own internal analog comparator, and P110 and P111 are the input pins of the comparator. Using this analog comparator can realize the hypoxia protection function. AT89C2051's instructions are fully compatible with INTEL’s MCS-51 series single-chip microcomputers. It has a 2K byte flash programmable and erasable read-only memory. The use of this chip can greatly simplify the design of the circuit. The use of this chip also realizes heating The other functions of the device are not described here. The thermocouple adopts the K-type thermocouple. The thermoelectric potential signal it receives is amplified and processed by the amplifier and then connected to the single-chip microcomputer. The thermocouple also plays a role in collecting the temperature signal of the constant open flame in the heater. The potential signal of the potentiometer is 1815mV, and its reference terminal is connected to a stabilized voltage source 358B-25.
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