Page 331 - Mechatronics with Experiments

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JWST499-c05
JWST499-Cetinkunt
ELECTRONIC COMPONENTS FOR MECHATRONIC SYSTEMS 317
V
C1

+5 V
Digital
data
0/1

V
C1

Relay

+5 V
Digital
data
0/1

V Load
+5 V C1
Digital
data SCR
0/1

FIGURE 5.51: ON/OFF control using a digital computer data bus line: (a) LED (ON/OFF) light
output, (b) relay ON/OFF control, (c) SCR control in an AC circuit. In all cases, a transistor is
used as an electronic switch between the computer and the output circuit.

in this example, since no flip-flop is used, the data line must be dedicated for the control of
this relay.

Example Figure 5.51 shows various interfaces between a digital computer data output
line and an ON/OFF output device through a transistor. In case 1, an output LED light is
turned ON/OFF by the computer data bus via a transistor. In case 2 and 3, a relay and a
SCR are controlled (turned ON/OFF) respectively. By controlling the timing of the SCR
gate signal, a proportional control is approximately achieved.