Aftab

Smith & Corripio, 3rd edition
Problem 1-1. Automation in daily life.
Identificaton of the M-D-A components, controller type, instrumentation diagram, and type of control.

(a) House air-conditioning/heating.
M: Temperature element TE in thermostat TE/C D: Mercury switch in thermostat TE/C A: Solenoid S that turns unit (AC/H) on and off. The controller is On/Off and the control is feedback.

SP
TE/C S AC /H

(b) Cooking oven.
M: Temperature element TE, usually a gas-filled bulb D: Temperature controller TC. A: Solenoid S that operates the heating element in the oven The controller is On/Off and the control is feedback on the temperature variable.

SP TC TE S

(c) Toaster.
M, D, A: temperature element/controller TE/C. Usually a bi-metallic strip that pushes the latch on the mechanism holding the slice of bread. The bread is released and the heating element de-energized when the temperature reaches the value set by the set point. The controller is On/Off and the control i feedback with respect to temperature.,

SP

TE/C

(d) Automatic sprinkler system for fires.

M, D, A: temperature element/controller TE/C, a rod that gives to the water pressure at a set temperature, allowing the water to spray over the fire. The controller is On/Off with single action, and the control is feedback.

TE/C

Water main

(e) Automatic cruise speed control.
M: Speed sensor and transmitter ST on the transmission D: Speed controller SC A: Damper on air intake to the engine throttles the air varying the power delivered by the engine Controller is regulating and control is feedback.

SP SC ST S Air

Transmission

Engine

(f) Refrigerator.
M: temperature sensor TE, usually a gas-filled bulb D: Temperature controller C, mechanically linked to the sensor A: Solenoid S that turnsd the refrigeration compressor on and off The controller is On/Off and the control is feedback.
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