Diagram SOlution

This is a compact three transistor, regenerative receiver with fixed feedback. It is similar in principle to the ZN414 radio IC which is now no longer available. The design is simple and sensitivity and selectivity of the receiver are good.

AM Receiver Schematic

Notes:
All general purpose transistors should work in this circuit, I used three BC109C transistors in my prototype.The tuned circuit is designed for medium wave. I used a ferrite rod and tuning capacitor from an old radio which tuned from approximately 550 - 1600kHz. Q1 and Q2 form a compund transistor pair featuring high gain and very high input impedance. This is necessary so as not to unduly load the tank circuit.

The 120k resistor provides regenerative feedback,between Q2 output and the tank circuit input and its value affects the overall performance of the whole circuit. Too much feedback and the circuit will become unstable producing a "howling sound". Insufficient feedback and the receiver becomes "deaf". If the circuit oscillates,then R1s value may be decreased; try 68k. If there is a lack of sensitivity, then try increasing R1 to around 150k. R1 could also be replaced by a fixed resisor say 33k and a preset resistor of 100k. This will give adjustment of sensitivity and selectivity of the receiver.

Transistor Q3 has a dual purpose; it performs demodulation of the RF carrier whilst at the same time, amplifying the audio signal. Audio level varies on the strength of the received station but I had typically 10-40 mV. This will directly drive high impedance headphones or can be fed into a suitable amplifier.

Construction:
All connections should be short, a veroboard or tagstrip layout are suitable. The tuning capacitor has fixed and moving plates. The moving plates should be connected to the "cold" end of the tank circuit, this is the base of Q1, and the fixed plates to the "hot end" of the coil, the juction of R1 and C1. If connections on the capacitor are reversed, then moving your hand near the capacitor will cause unwanted stability and oscillation.

Finally here are some voltagee checks from my breadboard prototype.This should help in determining a working circuit:

All measurements made with a fresh 9volt battery and three BC109C transistors with respect to the battery negative terminal.

Q1 (b) 1.31V
Q2 (b) 0.71V
Q2 (c) 1.34V
Q3 (b) 0.62V
Q3 (c) 3.87V

This is the latest version of the Improved Infrared Receiver with Status LED which can control any desktop PC with an ordinary remote control. The project comes along with a small PCB in order to save space. It connects to the serial port as stated in the schematic and uses the freeware Girder (www.girder.nl) software together with Igor’s Plugin (www.cesko.host.sk/girderplugin.htm) to send commands to the PC. The potential uses of this device are countless (control MP3 players, CD and DVD players, radio and TV cards, even move the mouse cursor and shutdown the computer remotely !). Again, note that any ordinary remote control can be used by training Girder to learn its signals !



Project Image




Parts list:
R1 3.3K 1/4W
R2 10K 1/4W
R3 100K 1/4W
R4 10K 1/4W
R5 100K 1/4W
R6 220 1/4W
D1 1N4148
D2 LED 3mm
C1 4.7uF/16V Electrolytic
Q1 BC548
Q2 BC558
IC1 78L05
IC2 TSOP 1736/38/40 (may work with Siemens SFH506xx receivers also)
E1 CR2032 3V battery + PCB base
Misc Three pins to connect the serial cable (optional)

The improvements of this project compared to the ones already published in the internet is that it uses regulated power for the infrared receiver module (TSOP 17xx), has improved sensitivity (worked at a distance of about 10 m), and features a status led which is powered by an external battery source and is driven by two transistors. Upon signal reception, the led blinks to provide a visual feedback to the sender.

Infrared Receiver with Status LED Circuit Daigram




The PCB features narrow tracks (16 mil) so special care should be paid during the construction. The 4.7 uF capacitor is bent towards the board in order to save height if the circuit is to be placed in a small plastic box.



The Girder software for this project was preferred because it is first of all freeware, it is stable and customizable, features a large number of commands and supports user plugins. It is a bit difficult to learn at first, but after a while it deploys a great number of possibilities that other programs (even commercial ones) lack. Nevertheless, with the right corrections (pin changes) this project may be used with other software (WinLIRC, IRAssistant, Miriam, PCRemote) but no such testing has been carried out yet. This is maybe a good point for further search.

ΙR Reciever Pin Numer
Source 7 (RTS)
Ground 5 (GND)
Read 1 (DCD)

Just as in the transmitter circuit, the series of FM Wireless Microphone Receiver Hi Fi also uses an FM audio receiver module. Module used in the circuit FM Wireless Microphone Receiver Hi Fi has a good feture, namely audio FM receiver module has a function that is able to muffle the noise squel. Audio FM receiver module that is used in FM Wireless Microphone Receiver Hi Fi also does not require a lot of supporting components in the RF signal reception.

Audio FM receiver module only requires a 5 volt DC voltage source and a potentiometer P2 to set the threshold level of noise that will be muffled. Voltage source to an audio FM receiver module is also to go through the regulator is good, because if the quality of resources kuran it will generate noise. At the output line installed capacitors C3 and C4 as a couple and compensator for output in accordance with the amplifier or mixer (100mV rms).

To provide an output signal according to the needs and stable output signal audio FM receiver module on FM Wireless Microphone Receiver Hi Fi is fed to an audio preamplifier which uses IC TLC272. Levelk audio signal set by potentiometer P1. As a voltage regulator for power source circuit FM Wireless Microphone Receiver Hi Fi LM7805 regulator IC is used.