The AllenBradleySLC500 is a small frame programmable logic controller. It also includes discrete, analog, special I/O modules and related peripherals. The SLC500 controller has strong processing power, and its communication network, functional modules and storage capacity can be flexibly selected and configured. RSLogix500 ladder diagram programming software provides a convenient editing, development environment, users can click and select the configuration I≤O module. It is also equipped with a powerful symbolic database editor and fault diagnosis capabilities to help developers save time and maximize productivity. PLC small size, light weight, easy to install. The input and output system of PLC can intuitively reflect the changing state of the field signal, and can intuitively reflect the operating state of the control system in various ways, such as internal working state, communication state, I/O point state, abnormal state, and power state. There are some compelling instructions, which are very beneficial for operators and maintenance personnel to monitor the system. 1756-L71 Function Description The input signal type supplied to the programmable controller can be switched, analog, or digital. Generally speaking, the input unit consists of two parts: one is the interface circuit connected to the controlled device, and the other is the input image register.

The input unit receives various control signals from the user device, such as limit switches, operation buttons, select switches, jump switches, and other sensors. Through the interface circuit, these signals are converted into signals that the central processor can recognize and process, co-existing with the input image register. The runtime cpu reads the input information from the input image register and processes it, and stores the processing result in the output image register.

In order to prevent various interference signals and high voltage signals from entering the PLC, affecting its reliability or causing equipment damage, the field input interface circuit is generally isolated by photoelectric coupling circuit. The key device of photocoupled circuit is the optocoupler, which is usually composed of light-emitting diode and phototransistor. Generally, the PLC input types can be DC (DC24V), AC and AC and DC. Power to the input circuit is provided externally. Some can also be supplied from within the PLC. For DC input, according to the form of the field input interface circuit, it is divided into two types: source input and host input. The vast majority of European and American PLCS use leakage inputs, while the vast majority of Asian PLCS use source inputs.

The PLC is connected to the control object through the input/output terminal. The input and output end of the PLC usually has three forms of organization, namely, the point type, the group type and the separate type. The input end of PLC mostly adopts the sink type, and some PLC adopts the grouping type to increase the flexibility of use.

Collect temperature, pressure, flow, and according to the collected data to control the heating flow, to achieve the purpose of energy saving. According to the change of outdoor climate, by adjusting the opening of the electric valve of the original pipe network, the return temperature of the secondary pipe network can be controlled in time. By scheduling the given control curve, the operating parameters of each heat exchange station are within the given range. Colleagues, the central control room performs remote control of the scheduled electric valve and adjusts the operating parameters according to the needs. gprs dtu system configuration, can achieve temperature control, filling remote control pump frequency conversion. The upper computer selects the configuration king configuration software, combines with the database, stores and analyzes all data, and can cooperate with the optimization software for priority control.