This paper introduces the design of a flame controller based on STC12C5A single-chip computer. The flame controller is mainly used in industrial boiler control system.
It detects whether there is a flame in the boiler by ultraviolet sensor and achieves the corresponding control requirements. This device is composed of the smallest system of single chip microprocessor, actuator unit, ultraviolet sensor, key and display module. If the start button is pressed to start the ignition function and turn on the corresponding gas valve of small natural gas, the ignition time can be set by dialing switch, and the ignition transformer can be closed. If there is a flame in the boiler, start the corresponding gas valve of large natural gas. If the flame can not be detected for one second in a row at this stage, close all natural gas. Valve. In this paper, the design process of each module is described.
Finally, the equipment is debugged comprehensively. In the combustion process of industrial boilers, if combustion instability not only affects combustion efficiency, but also causes furnace extinction and even boiler explosion accidents. In order to prevent unstable combustion of boilers, it is necessary to be able to detect and deal with the combustion situation in time. The flame controller is very important in the process of combustion control of industrial boilers. This paper focuses on the design of a flame controller based on stc12c5a single chip microcomputer. This kind of flame controller has been stably applied in the monitoring system of many industrial boilers. When the flame is extinguished under abnormal conditions, confirm that it is correct, close the natural gas solenoid valve, and start the alarm device until the alarm is artificially lifted. Boiler fuel releases ultraviolet and infrared rays when burning.
Honeywell flame detector C7035 is used in this flame controller system to detect ultraviolet radiation released by flame. C7035 is a kind of flame detector with dynamic self-inspection, high resolution and high reliability, which is specially applied to the combustion detection of industrial boilers. When C7035 receives the flame signal, the larger the flame intensity, the smaller the internal resistance, and the higher the voltage on the sampling resistance. The flame intensity can be judged according to the voltage.
The control device of this system is driven by four relays, which are small fire solenoid valve control module, large fire solenoid valve control module and alarm control module. The detection part is composed of an initial time setting dial switch, a start button and a C7035 flame detection sensor. The initial time setting dial switch can set the continuous ignition time of the system (the ignition time is adjustable for 4, 6, 8, 10 seconds). The system detects that the start button is triggered along the descending edge and is stable in the closed state. It confirms that the start-up ignition system is controlled by a single-chip computer to start the small-fire solenoid valve, release natural gas, and turn on the ignition transformer to ignite and ignite. When the time is up, turn off the ignition transformer and judge whether the flame in the boiler is normal.
If the flame in the boiler is abnormal after the ignition time, close the small fire solenoid valve and alarm; if the flame is normal, start the large fire solenoid valve, and the boiler works normally. During the operation of the boiler, the high and low fire solenoid valves are opened, and the flame combustion in the boiler is monitored at any time. If the “black fire” or flame out status is found to last for one second, immediately close the corresponding solenoid valves of high and low fire and start the audible and visual alarm device. The system is required to record the last 10 alarm records. This flame control system is based on STC12C5A60S2 single-chip computer. It collects the flame intensity by using AD conversion function inside the single-chip computer, and displays the flame intensity by using three LED indicators. The burning LED 1 is on, and the flame intensity is high. All three LEDs are on. The function of internal timer of single chip computer is used to control the running time of the system. The driving relay controls ignition transformer, small natural gas solenoid valve, large natural gas solenoid valve and alarm module. The concrete structure block diagram is shown in Figure 1. In the flame control system, STC12C5A60S2 MCU is the core of the whole controller.
The performance of the flame controller depends on the superiority and stability of the monolithic computer and the flame detection sensor selected by the system. STC12C5A60S2 monolithic computer is a strong encryption type, with AD conversion function, good anti-interference performance, low power consumption, support for online programming, including internal watchdog, power supply by DC 5V, and has 36. I/O ports [1]; streamlined instruction structure runs faster and cheaper; compatible with 51 single-chip microcontroller supports C language development [2]. The flame detection sensor system uses Honeywell flame detector C7035 with dynamic self-detection, high resolution and high reliability to detect the ultraviolet radiation released by the flame. The schematic diagram of the flame sensor is shown in Fig. 2. The system is divided into two modes, setting mode and working mode. Setting mode is used for administrators to set ignition time by dialing switch according to different system requirements before using. In the working mode as shown in Fig. 3, the ignition time is set first, then the modules are initialized, waiting for the administrator to press the start button, the relay of the single chip computer starts the electromagnetic valve corresponding to the small natural gas, releases the natural gas, and turns on the ignition transformer to ignite. After the ignition time arrives, the ignition transformer is turned off and C7035 is collected. The return voltage is used to judge whether the flame in the boiler is normal or not. If the flame is normal, start the fire solenoid valve and the boiler works normally. If the flame in the boiler is abnormal after the ignition time has arrived, then close the small fire solenoid valve and alarm.
In the process of boiler operation, both large and small fire solenoid valves are opened, and the flame combustion situation in the boiler is monitored at any time. If the “black fire” or flame extinction status is found to last for one second, the corresponding solenoid valves for large and small fires are immediately closed and the sound and light alarm device is activated. It is necessary for managers to check the boiler condition and then re-close the alarm procedure. The system EEPROM is required to record the last 10 alarm records. During the operation of the system, the last 10 alarm records are required to be recorded. The controller uses 24C02 memory to save the data. The system automatically saves the relevant alarm data in EEPROM at each alarm.
The system requires to be able to query alarm information. The flame controller requires that no matter what mode the system is in, once the sensor fails or the flameless condition is detected continuously for one second in the system operation, the natural gas solenoid valve should be cut off immediately and switched to the alarm mode. Therefore, the interruption mode of the alarm module should be adopted. After the interruption triggers, thermostatic element besides the alarm module, the alarm module should be modified. Information to EEPROM. Because the time requirement involved in the flame controller is not strict, the system directly uses the internal timer of the single chip computer to time. On the basis of STC12C5A60S2 MCU as the core, the flame controller adopts the flame detection sensor C7035 to detect the relevant data, and the alarm module adopts the form of interruption, and adds the functional keys to restore the factory settings before starting.
During the debugging process, it was found that the flame sensor C7035 was unstable, and the power supply and voltage divider circuit were not well designed. In the debugging stage, the internal EEPROM was used to save the relevant data. In the small batch test, the phenomenon of data loss was found, and then 24C02 was added to solve the problem. The design cost of the flame controller is low and has high practical application value. Now it has been produced in large quantities and operates steadily.