Lights and Display Board Circuits

# Simple IrDA Transmitter Schematic Circuit Diagram

Communication over the IrDA port uses a relatively complex protocol but its possible to send a single character using just a few components. In many cases, this will be sufficient to control a Palmtop. This circuit generates a single pulse of IR light that is interpreted by the Palmtop as a data byte with the value 255. The circuit could hardly be simpler, a 1 μF capacitor is charged via the 27 kΩ resistors and when the switch has pressed this charge will flow through the diode to generate an IR light pulse.

The values have been optimized for a communication speed of 9600 Baud but the actual pulse length is not critical. The listing shows a simple receiver program for this IrDA signal. The IR interface is opened with the command ir and the line get\$(#5,0) reads a single byte from the interface, if nothing has been received it will return –1. Each time a character is received a counter will be incremented and displayed on the screen and a short sound will be generated.

#irdacount.bas
open “com1:”,9600,ir as #5
z=0
draw -1
while 1
n =get\$(#5,0)
if n>-1
z=z+1
t\$=str\$(z)
draw t\$,75,60,2
sound 800,100,63
endif
wend

A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, divide voltages, bias active elements, and terminate transmission lines, among other uses. A resistor is an electrical component that limits or regulates the flow of electrical current in an electronic circuit. Resistors can also be used to provide a specific voltage for an active device such as a transistor.

The resistor absorbs the electrical energy in the process where it acts as a hindrance to the flow of electricity by reducing the voltage, and it is dissipated as heat. In today’s world of electronic circuits, heat dissipation is typically a fraction of a watt. Examples of variable resistors are rheostat and digital potentiometer. Rheostats are electrical components made of a resistive wire wound around a ceramic core. In the past, they were used to control the amount of power in motors, heaters, and ovens.
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