Power SuppliesSignal Generators

Simple IrDA Receiver Schematic Circuit Diagram

Palm Pilots are just one of the devices that use the IrDA
standard for infrared data communication. Most Desktop PCs are not equipped with an IrDA interface so this simple circuit conveniently converts the PC serial port into an IrDA receiver. The circuit needs to detect
and stretch the received infrared pulses so that the output signal conforms to the standard serial data format. The circuit is designed to operate at 9600 Baud and uses just two NPN transistors and a phototransistor.

Simple IrDA Receiver Schematic Circuit Diagram

The 22-nF capacitor performs the job of lengthening the signals. It is important to ensure that the DTR signal is set to a high state on the serial port settings because this signal is used as the power supply to the circuit.
The sample program listed below is written in HotPaw Basic for the Palm and tests the interface by sending a short greeting followed by a sequence of integers.

#irdatx. bas
open “com1:”,9600, ir as #5
print#5,” Hello”
for n= 1 to 100
print#5,n
a= fn wait(1)
next n
close #5
end

NPN transistors are a type of bipolar transistor with three layers that are used for signal amplification. It is a device that is controlled by the current. A negative-positive-negative transistor is denoted by the abbreviation NPN. Since most of the charge carriers in N P N transistors are electrons, their electron mobility rates are high. N P N transistors provide better conductivity than P N P transistors for this reason. Due to their fast switching rates, N P N transistors are preferred for switching applications.

The NPN transistor is designed to pass electrons from the emitter to the collector (so conventional current flows from collector to emitter). The emitter “emits” electrons into the base, which controls the number of electrons the emitter emits.
You can use any NPN-type transistor (for example 2N3904, BC547, BC548, BC549, etc.) These are basic circuits, so they can be improved (with diodes for reverse voltage protection, for example), or can be simplified (XOR, XNOR gates), but for start, we will stick with these basic circuits.
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