BH1417 Stereo PLL FM Transmitter Circuit

Here is my YouTube video Hindi version about this circuit:

This BH1417 pll fm transmitter includes features like: pre-emphasis, sound limiter, stereo transmission, low pass filter, pll circuit, fm oscillator and rf output buffer. The sound limiter maintains the same audio level so no distorsions occur, the stereo encoder separates the left and right channel enabling stereo transmission, the low pass filter blocks any audio signal above 15 Khz to prevent rf interference and the pll circuit provides a rock solid frequency stability.

There are 14 possible transmission frequencies with 200KHz increments selected with a 4-DIP switch. Starts from 88.7 up to 89.9 MHz and 107.7 up to 108.9 MHz.

S4	S3	S2	S1	Frequency
1	1	1	1	88.7 MHz
1	1	1	0	88.9 MHz
1	1	0	1	89.1 MHz
1	1	0	0	89.3 MHz
1	0	1	1	89.5 MHz
1	0	1	0	89.7 MHz
1	0	0	1	89.9 MHz
1 = ON, 0 = OFF

Simply select transmission frequency at which you would like to transmit, set the combination for 4-DIP switch and BH1417 will tune to that frequency. If you can’t hear the transmitted audio signal on your FM receiver then re-adjust 2.5 turn variable coil until you can hear the signal.

Technical Specifications
Supply Voltage: 4 – 6V
Transmission Frequency: 87.7 – 88.9MHz, 106.7 – 107.9MHz (200kHz steps)
Output RF Power: 20mW
Audio Frequency: 20 – 15KHz
Separation: 40dB
Power Consumption: 30mA

Components

1x BH1417 – Stereo PLL Transmitter IC (Case SOP22)
1x 7.68 MHz Crystal
1x MPSA13 – NPN Darlington Transistor
1x 2.5 Turns Variable Coil
1x MV2109 – Varicap Diode
1x 4-DIP Switch
ANT – 30 cm of copper wire

1x 22K Resistor
7x 10K Resistor
1x 5.1K Resistor
2x 3.3K Resistor
1x 100 Ohm Resistor 1x 100uF Capacitor
3x 10uF Capacitor
2x 1uF Capacitor

1x 47nF Capacitor
3x 2.2nF Capacitor
1x 1nF Capacitor
1x 330pF Capacitor
2x 150pF Capacitor
1x 33pF Capacitor
2x 27pF Capacitor
1x 22pF Capacitor
2x 10pF Capacitor

Pyroelectric Infrared Sensor Module DIY Kit Anti-theft Circuit Sensor Module DIY Kits

Here is my video supporting this article:

Description of Home security system:
There are several home security systems out there. Different manufacturers use different techniques and topology in their design. Cameras are also very popular for the purpose of security. Main problem with security cameras is to monitor them. They have capability to record the view in DVR hard drive but they could not stop intruder from intrusion. They are just providing the proof after the incident happens. Whereas in most cases we want to stop an intruder from intrusion. for this purpose different types of alarming systems are developed which warns the intruders not to enter in a specific area. also these system are kind of passive systems which needs only power up and they stays in sort of sleeping mode when everything is normal. They activate an alarm at the time of intrusion. They don't normally need to observe. So such systems are better in the way that all the time monitoring is not needed. Monitoring all the time is not easy. It needs a team of three people minimum all the time to observe the cameras in 24 hours a day. In some very sensitive areas it is mandatory to keep system system in observation all the time but in normal situations an alarming system with no observation is the best choice. Such alarming systems use sort of activating sensing system which is activated by some parameter. mostly they use pyroelectric sensor which are activated by human body temperature. When a person is passing through the pir or piroelectric sensor, its body infrared radiation which is in the form of body temperature activates the pyroelectic sensor and it sends its output signal to an amplifier. The amplifier is amplifying the signal as well there is a timer operation also in the circuit. The amplifier activates a alarm which informs the intruder not to enter in the specific area as you are under observation.

Principle of operation:

1. When power is applied to the circuit, The pir sensor or piroelectric sensor senses human passed in front of it and it produces an electrical signal, the pir sensor output signal from sensor pin 2 is applied to one transistor VT1 and here it is amplified. Without amplification the signal is small enough so that it could not be fed to the next stage, then this signal is applied to the operational amplifier IC2A pin 3 which performed as high gain low noise amplifier stage, and latter the signal is supplied to IC1A for further amplification.
2.  The IC2B works like a voltage comparator and it compares the two inputs. One is the signal coming from the prvious stage and the other is the reference provided by R10 and VD1. Transistor VT is used to drive the output buzzer.