122-28176 Parallax Inc, 122-28176 Datasheet - Page 186

• Manufacturer Part Number: 122-28176
• Description: GUIDE STUDENT PROCESS CONTROL
• Manufacturer: Parallax Inc

Specifications of 122-28176

• Accessory Type: Manual
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: Propeller Education (PE) Kit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant

Page 176 · Process Control
The BASIC Stamp is simply energizing an LED in the SSR. The LED's light energizes a
current switching device, a TRIAC, to control 240 VAC to the load. The SSR uses
optical coupling and therefore complete electrical isolation between the low voltage
BASIC Stamp circuit and high voltage load circuit.
The
command should not be used to regulate the power to the load. The frequency
PWM
of household electricity is 60 Hz, and the period of a single wave equals 16.67 ms, as
shown by the “a” and “b” labels in Figure 5-30. The PWM pulse is around 9 µs (1/112
kHz), which would not provide effective control of the SSR. Using
and
HIGH
LOW
commands to control the SSR, as was done in the first part of Activity #2, will provide
better control. Figure 5-30 illustrates energizing the AC output with a 50% duty cycle of
50 ms on and 50 ms off.
Figure 5-30 PWM of AC with 50% Duty and Period of 100 ms