Mini FM Transmitter Schematic Circuit Diagram with explanation

This is a some what powerful transmitter.Here I have used famous Transistor 2N2222.This circuit operates with 3V power supply.To make L1 wind 5 turns of 24AWG wire on a 1cm plastic former.

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rain sensor circuit diagram using NE 555

This is a Rain detector alarm circuit.You can keep the sensing part out of the house.If water drops fell on the sensing part the alarm will start to ring.so this is very useful circuit for you.Here we have used common IC NE 555.Think and use this in different way..

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Speach Amplifier circuit diagram with explanation

This circuit is intended to be placed in the same box containing the loudspeaker, forming a compact microphone amplifier primarily intended for speech reinforcement. A device of this kind is particularly suited to teachers, lecturers, tourists' guides, hostesses and anyone speaking in crowded, noisy environment. The circuit's heart is formed by the TDA7052 Audio power amplifier IC, delivering a maximum output of 1.2W @ 6V supply. An external microphone must be plugged into J1, its signal being amplified by Q1 and fed to IC1. R1 acts as a volume control and C3 tailors the upper audio frequency band, mainly to reduce the microphone possibility of picking-up the loudspeaker output, causing a very undesirable and loud "howl", i.e. the well known Larsen effect. Therefore, C3 value can be varied in the 4n7 - 22nF range to ensure the best compromise from speech tone quality and minimum Larsen effect occurrence. Dynamic or electrets microphone is warmly recommended. It has a useful feature that can be used to momentarily mute the microphone by connecting SW1 shown in diagram.







Parts:

P1 = 22K
R1 = 1M
R2 = 15K
R3 = 470R
R4 = 47K
R5 = 4.7K
R6 = 4.7K
C1 = 100nF-63V
C2 = 100nF-63V
C3 = 10nF-63V
C4 = 100nF-63V
C5 = 220uF-25V
C6 = 10uF-25V
Q1 = BC547
IC1 = TDA7052 B1
J1 = Mono Jack Socket
B1 = 6V Battery
SW1 = SPST Slider Switch
SW2 = SPST Toggle Switch



Notes:

* Please note that hands-free, uni-directional headset or ear clip microphone types are very well suited for this device, as also are Clip-on Lavaliere or Lapel microphones.
* If a small electrets capsule is used for the microphone, R5, R6 and C6 must be added to the circuit to provide power supply.
* Choose a loudspeaker as large as possible, in order to increase circuit performance.
* You can use also two 4 Ohm loudspeakers wired in series or two 8 Ohm types wired in parallel in order to obtain better results.
* The box containing the amplifier and loudspeaker(s) can be fitted out with a belt and carried like a shoulder-bag or, if you build a smaller unit, it can be used as a Pick & Go Belt Clip Speaker.

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Simple basic Intercom Circuit with explanation

This is a intercom circuit diagram.you can use this for your office or for your working place.Acoording to the changes of s1a and s1b You can use this as the reciever and the mic



Note

# Use screen wires Between these two circuits

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Infrared motion detector circuit diagram with explanation

Here is the circuit diagram of an infrared motion detector that can be used to sense intrusions.Infra red rays reflected from a static object will be in one phase, and the rays reflected from a moving object will be in another phase.The circuit uses this principle to sense the motion.






The IC1 (NE 555) is wired as an astable multivibrator .The IR diode connected at the output of this IC produces infrared beams of frequency 5Khz.These beams are picked by the photo transistor Q1 .At normal condition ie; when there is no intrusion the output pin (7) of IC2 will be low.When there is an intrusion the phase of the reflected waveforms has a difference in phase and this phase difference will be picked by the IC2.Now the pin 7 of the IC 2 goes high to indicate the intrusion.An LED or a buzzer can be connected at the output of the IC to indicate the intrusion.



Notes.

* Comparators IC2a and IC2b are belonging to the same IC2 (LM1458).So the power supply is shown connected only once.No problem.
* When there is disturbance in the air or vehicles passing nearby,the circuit may get false triggered.
* POT R5 can be used for sensitivity adjustment.

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QRP antenna tuner circuit diagram with explanation

Low power ( 3 to 30 MHz) transmitters constructed by hams are generally called QRP’s. For such transmitters a well tuned antenna is a must.If the impedance is not properly matched there will be a little or no output.But if properly matched there will be great results.A circuit for matching the antenna properly with the transmitter id given below.






The output of the transmitter is given to the input of the tuner( connector BNC1). The output of the tuner(connector BNC2) must be connected to antenna.Then adjust the L1 and C1 to obtain the maximum transmission power.The transmission power can be checked using a SWR meter.



Notes.

* Assemble the circuit on a goos quality PCB or common board.
* If the matching is not satisfactory then change the values of L1,C1,C2&C3 to the next close value and tune again.
* Proper tuning requires some trial and error.
* The circuit can be enclosed in an aluminum casing for better performance.

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Three Channel Audio Splitter circuit diagram with explanation

This circuit is suitable to amplify and distribute the audio signals. The input audio signal is applied to the J1 and after passing through the P1, It is buffered and amplified by the IC1 prepared to redistribute. It has 3 outputs to drive 3 audio lines with 300 ohms impedance.









Parts:

J1 = RCA Socket (See Notes)
P1 = 100K-Potentiometre
R* = 10K-100K
R1 = 560K
R2 = 1K
R3 = 2.2K
R4 = 2.7K
R5 = 2.7K
R6 = 330R
R7 = 330R
R8 = 330R
C1 = 100uF-25V
C2 = 100uF-25V
C3 = 100uF-25V
D1 = BZX79C18
D2 = BZX79C18
Q1 = BC337
Q2 = BC327
IC1 = NE5532-34



Notes:

* J1 will be RCA Audio input female socket.
* R* is on your choice it can be choose between 10K to 100K resistor.
* Output capacitor’s value is between 100uf to 470uf and power handling is 25V to 50V.
* You can power up this circuit via +12V/-12V regulated supply but you have to remove following parts Q1-Q2-C2-C3-D1-D2.
* Maximum power ratings +35V/-35V

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