Disclosure of Invention
Aiming at the problem of theory and reality combination in teaching experiments, the PID control characteristic experiment device for the constant temperature system is provided, the temperature is collected in real time, and the constant temperature control of a receptor is realized. The receiver constant temperature control system is required to operate normally, the temperature control range is 20-200 ℃, the interactive interface is reasonably designed, and the interactive interface needs to contain target temperature, real-time temperature, proportion P value, integral I value, differential D value, heating start, heat dissipation stop, heating stop and the change curve of the receiver temperature and time.
The technical scheme of the utility model is as follows: the utility model provides a constant temperature system PID control characteristic experimental apparatus, including the touch-sensitive screen, programmable logic controller, a weighing sensor and a temperature sensor, solid state relay, electric heater, fan and acceptor, through human-computer interface touch-sensitive screen input control temperature and PID parameter, programmable logic controller and touch-sensitive screen intercommunication, temperature sensor gathers the real-time temperature of acceptor and passes through temperature transmitter on, temperature transmitter output temperature data send programmable logic controller, programmable logic controller carries out PID control calculation output control signal and heats the acceptor through switching on or off control electric heater to solid state relay, programmable logic controller output control signal control fan cools down the acceptor, programmable logic controller outputs the real-time temperature of acceptor and shows to the touch-sensitive screen.
Preferably, constant temperature system PID control characteristic experimental apparatus still includes power supply circuit, including the circuit breaker, scram switch, starting switch, stop switch, ac contactor and switching power supply, circuit breaker one termination 220V alternating current, the scram switch of circuit breaker another termination series connection, starting switch, stop switch, the ac contactor coil, scram switch and stop switch are normally closed switch, starting switch is normally open switch, ac contactor normally open switch KM1 one end connects the circuit breaker lower extreme, ac contactor normally open switch KM1 another termination switching power supply input end, switching power supply output low pressure direct current termination touch-sensitive screen, programmable logic controller and temperature transmitter.
Preferably, the emergency stop switch, the start switch and the stop switch are switches arranged in a touch screen.
Preferably, the output end of the switching power supply is connected with an operation indicator lamp in parallel.
Preferably, the temperature sensor with the surface coated with the heat-conducting silicone grease is inserted into a temperature measuring hole in a receiver.
The utility model has the beneficial effects that: the PID control characteristic experiment device for the constant temperature system can provide a constant temperature control practice platform for students, can be repeatedly used, strengthens the teaching effect of the constant temperature control practice link, improves the manual practice capability of the students, and has the advantages of simple platform structure, convenient use, strong expansibility and easy popularization.
Detailed Description
The utility model is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.
The PID control characteristic experiment device of the constant temperature system shown in FIGS. 1 and 2 comprises a circuit breaker 1, an emergency stop switch 2, a start switch 3, a stop switch 4, an AC contactor 5, a 24V switching power supply 6, an operation indicator light 7, a touch screen 8, a temperature transmitter 9, an electric heater 10, a programmable logic controller 11, a fan 12, a solid state relay 13, a temperature sensor 14, a receptor 15 and a lead. As shown in the block diagram of the temperature control system shown in fig. 1, a human-computer interface touch screen 8 inputs a control temperature and PID parameters, a programmable logic controller 11(PLC) receives set data in the touch screen 8, the programmable logic controller 11 performs PID control calculation according to the PID parameters, outputs a control signal to control an electric heater 10 to heat a receptor 15 by turning on or off a solid-state relay 13, a temperature sensor on the receptor 15 collects a real-time temperature on the receptor 15 and sends the real-time temperature back to the programmable logic controller 11 through a temperature transmitter 9 for PID control calculation, and the programmable logic controller 11 simultaneously outputs a control signal to control a fan 12 to cool the receptor 15.
As shown in the circuit diagram of the constant temperature system PID control characteristic experiment device shown in fig. 2, the circuit breaker 1 is switched on, 220V electricity is conducted with the circuit, the emergency stop switch 2 and the stop switch 4 are normally closed switches, the start switch 3 (normally open switch) button is pressed, the coil of the alternating current contactor 5 is electrified and attracted, the switch KM1 of the alternating current contactor 5 is closed, the 220V electricity is conducted with the switch power supply 6, the switch power supply 6 outputs low-voltage direct current to supply power to the touch screen 8, the programmable logic controller 11 and the temperature transmitter 9, and the operation indicator lamp 7 connected with the output end of the switch power supply 6 in parallel is turned on. The touch screen 8 is communicated with the programmable logic controller 11, after the touch screen 8 is electrified, the touch screen enters an initialization interface, reads a compiled temperature control built-in program, and then enters a man-machine interaction interface of a constant temperature system PID control characteristic experiment system. A temperature value acquired by a temperature sensor (PT100) through a receptor is converted into a standard voltage value by a temperature transmitter 9 and is transmitted to a programmable logic controller 11, a temperature analog quantity is converted into a digital quantity by the programmable logic controller 11, the digital quantity is transmitted in real time through a communication cable and displayed on a touch screen 8, meanwhile, the programmable logic controller 11 carries out PID control, calculates and outputs a control signal to a solid-state relay 13, the solid-state relay 13 is conducted, and an electric heating 10 is conducted with a 220V power supply to heat the receptor. After the experiment is finished, the coil of the alternating current contactor 5 can be powered off by pressing the stop switch 4, the power supply loop is disconnected, and the circuit of the whole device finishes working. Similarly, abnormal work occurs in the experimental process, and the circuit can be disconnected by pressing the emergency stop switch 2. The switch in the circuit can be directly arranged in the touch screen 8, and the circuit can also be built by using an actual independent switch.
As shown in the PLC flowchart of fig. 3, when the PLC is powered on, the system starts to operate. When the main switch is turned on, the temperature measuring module works to synchronize the temperature value of the receptor into the PLC in real time. Parameters such as proportion, differentiation, integration, set temperature value and the like input by the touch screen can enter a PID algorithm in the PLC. The PLC sets three control conditions: when the measured value is smaller than the target value, the PID algorithm controls the solid-state relay so as to control the electric heater to heat the receptor. When the measured temperature is higher than the set temperature by +1 ℃, the PLC controls the solid-state relay so as to control the electric heater to stop heating the receptor; meanwhile, the PLC controls the fan to operate, and the receiver conducts forced convection heat dissipation. When the measured temperature is less than 1 ℃ of the set temperature, the PLC controls the solid-state relay, further controls the electric heater to stop heating the receptor, and simultaneously controls the fan to stop rotating, so that the receptor carries out natural convection heat dissipation. If the 'master switch' on the touch screen is closed, the PLC stops running.
Temperature measurement circuit design: when the temperature measuring circuit measures the temperature of the receptor, the temperature sensor coated with the heat-conducting silicone grease on the surface is inserted into a temperature measuring hole (cylindrical space) in the receptor. The value of the temperature sensor changes along with the change of the temperature of the receptor, the analog quantity is converted into the digital quantity through the programmable logic controller, the programmable logic controller converts the digital quantity result into the analog quantity after being processed through a program, and the analog quantity is connected with the touch screen through a communication cable to finally display the temperature value.
Designing a heating circuit: when the temperature measurement value is smaller than the set temperature value and a certain channel of the programmable logic controller controls the solid-state relay to be switched on, the 220V voltage is supplied to the electric heater to heat the receptor; on the contrary, when the temperature measured value is larger than the set temperature value, the channel control solid state relay is switched off, no current flows in the electric heater, and the heating is terminated.
Designing a heat dissipation circuit: when the temperature measurement value is greater than the set temperature value +1 ℃, when a certain channel of the programmable logic controller outputs current to the outside, the fan rotates, and the receptor carries out forced convection heat dissipation; when the temperature measurement value is less than the set temperature value +1 ℃, the channel is closed, and the fan stops rotating. The receptor and air carry out natural convection heat dissipation.
Target temperature, parameters such as proportion, integral, differential and the like can be set on the touch screen, and the parameters can be converted into corresponding instructions to be sent to the programmable logic controller. During the operation of the system, the actual temperature of the receptor is displayed in real time. And can display real-time curves of the actual temperature value and the set temperature along with the change of time. The touch screen is provided with a heating start, a heat dissipation start, a heating indicator light and a heat dissipation indicator light. The learner can visually see the actual running process of PID control after the PID parameters are set by setting the PID parameters and running the whole device, so as to further understand the PID control.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the utility model. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.