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Plant Security
Published in Frank R. Spellman, Fundamentals of Public Utilities Management, 2020
The three major types of electronic controllers are timers, electromechanical relays, and programmable logic controllers (PLCs), which are often called “digital relays.” Each of these types of controllers is discussed in more detail below. Timers use internal signal/inputs (in contrast to externally generated inputs) and generate electronic output signals at certain times. More specifically, timers control electric current flow to any application to which they are connected, and can turn the current on or off on a schedule pre-specified by the user. Typical timer range (amount of time that can be programmed to elapse before the timer activates linked equipment) is from 0.2 seconds to 10 hours, although some of the more advanced timers have ranges of up to 60 hours. Timers are useful in fixed applications that don’t require frequent schedule changes. For example, a timer can be used to turn on the lights in a room or building at a certain time every day. Timers are usually connected to their own power supply (usually 120–240 V).
Plant Security
Published in Frank R. Spellman, Handbook of Water and Wastewater Treatment Plant Operations, 2020
The three major types of electronic controllers are timers, electromechanical relays, and programmable logic controllers (PLCs), which are often called “digital relays.” Each of these types of controller is discussed in more detail below. Timers use internal signal/inputs (in contrast to externally generated inputs) and generate electronic output signals at certain times. More specifically, timers control electric current flow to any application to which they are connected, and can turn the current on or off on a schedule pre-specified by the user. Typical timer range (amount of time that can be programmed to elapse before the timer activates linked equipment) is from 0.2 seconds to 10 hours, although some of the more advanced timers have ranges of up to 60 hours. Timers are useful in fixed applications that don’t require frequent schedule changes. For example, a timer can be used to turn on the lights in a room or building at a certain time every day. Timers are usually connected to their own power supply (usually 120–240V).
Upgrading Security
Published in Frank R. Spellman, The Drinking Water Handbook, 2017
The three major types of electronic controllers are timers, electromechanical relays, and programmable logic controllers (PLCs), which are often called digital relays. Timers use internal signals or inputs (in contrast to externally generated inputs) to generate electronic output signals at certain times. More specifically, timers control electric current flow to any application to which they are connected and can turn the current on or off on a schedule prespecified by the user. Typical timer range (amount of time that can be programmed to elapse before the timer activates linked equipment) is from 0.2 seconds to 10 hours, although some of the more advanced timers have ranges of up to 60 hours. Timers are useful in fixed applications that do not require frequent schedule changes; for example, a timer can be used to turn on the lights in a room or a building at a certain time every day. Timers are usually connected to their own power supply (usually 120 to 240 V).
Automation and Control of a Multi-feedstock Biodiesel Production Plant
Published in IETE Journal of Research, 2023
Ilesanmi Daniyan, Lanre Daniyan, Adefemi Adeodu, Felix Ale
Figure 6 explains how the process control of the operating conditions was carried out. The figure shows the control circuitry for the integration of the pumps, motor and tanks into the control panel. Pump 1 (P1) services tank 1 (oil storage tank), tank 2 (oil-pretreatment tank) and tank 5 (main reactor), while Pump 2 (P2) services T3 (methanol tank), T4 (mixing tank) and tank 5 (reactor). On the other hand, P3 services tank 5 (reactor) and the washing tank (tank 6) and the water tank (tank 7). M1 (electric motor 1) services tank 2 (oil-pretreatment tank), M2 (electric motor 2) services T4 (mixing tank) while M23 (electric motor 3) services T5 (reactor). All the pumps and electric motors are integrated into the control panel. For the heating element and temperature control, a thermocouple (type K) is fixed to each of the heating element connected to the pre-treatment tank, mixing tank and main reactor. This is to measure the temperatures in these tanks. A temperature transmitter (AD595) converts the measured value of temperature from the temperature sensor from analogue to a digital signal, amplifies the converted signal and transmits it as a standard output signal to the microcontroller (8-bit Atmel ATmega328p) for control actions. Already the threshold values of the temperatures for these tanks have been pre-set on the microcontroller. The microcontroller compares the measured signal to the range of the threshold value If the measured temperature is higher than the threshold, the micro controller turns OFF the contactor, which deactivates the heater and vice versa. The temperature probe is the temperature sensor while the Arduino micro controller is the main controller. The actuator is the contactor, that either activates or deactivates the heater, based on the control signal from the main controller. The internal timer (TIMER 0) is a form of an embedded system inside the microcontroller that is connected to a buzzer, to measure time intervals and generate delay. Once there is an error that requires the attention of the operator, the buzzer sends an alarm through a transistor circuit that is configured as a switch. The integration of these control elements and mechanisms is illustrated in Figure 7.