Data Entry from the Screen
Richard J. Smythe · Apress eBooks · 2021
A control system must include the capability of entering data from the screen, to be able to modify or vary the operation of a sequence or process. In this chapter, numerical values entered from the keyboard are used to modify scripted sequences of programming code that oscillate LEDs on and off for a predetermined number of cycles. In addition, two options are created for the modes of power control in which the illumination for the diode cycles from full on to off and the diode output intensity is incrementally stepped from off to full brightness to create a “fade” or “fading” effect. LED brightness is determined by the current through the device. The maximum current through the LED is set by the current limiting resistor (CLR) placed in series with the diode, power source, and ground. The current through the LED can be regulated by varying the voltage of the supply. However, diode intensity control by voltage variation can only be effective above the voltage level required for conduction in the device, typically 1.8–3 volts.