TWEETER CROSSOVER CIRCUIT

1. A single coil speaker is not good in handling high and low frequency at the same time.
2. If we could filter out the low frequency and play it through a tweeter ,it will produce more sound quality than using a single speaker.
3.  This is what is realized here.
4.  Here the high frequencies are filtered out using a low pass filter made of C1,C2 and R1 and send to the tweeter.The low frequency is only fed to the woofer.

   
   

   
   
   

   NOTES:
   

   • The tweeter can be a 2 to 3 inch, 4 to 8 Ohm one .

   •  R1 is used to adjust match the the tweeters output level to that of woofer.

   • C1 and C2 are electrolytic capacitors.

   • R1 should be rated more than 2 Watts.

   
   
   
   

   
   

LED TOURCH USING MAX 660

1. This is a simple LED torch circuit based on IC MAX660 from MAXIM semiconductors.
2. The MAX 660 is a CMOS type monolithic type voltage converter IC. 
3. The IC can easily drive three extra bright white LEDs.The LEDs are connected in parallel to the output pin 8 of the IC.
4. The circuit has good battery life. The switch S1 can be a push to ON switch.

   
   
   NOTES:-
   

   • Assemble the circuit on a general purpose PCB.

   • The IC must be mounted on a holder.

   • The circuit can be powered from two torch cells connected in series.

   • The capacitors C1 and C2 must be Tantalum type.

   • The diodes D1 to D3 must be of 1N4148.

   
   
   
   

   
   

CW PRACTICE OSILLATOR

1. 1. A circuit diagram that can be used for the generation of CW Morse code is shown here.
      
   2.  This circuit can be very useful those who would like practice Ham Radio.
   3.  The circuit is nothing but an astable multivibrator based on NE 555.The frequency of oscillations of the circuit depends on the components R1,R2 & C1.The circuit can be powered from a 9V PP3 battery. .

   
   
   
   
   

   NOTES:

   • The POT R2 can be used for frequency adjustments.

   • POT R3 can be used for volume adjustments.

   • The switch S1 can  be a Morse code key.

   
   

10V SWITCHING REGULATOR USING LM5007

1. The circuit diagram shown here is of a 10V switching regulator based on the LM5007 from National Semiconductors.
2. The LM5007 is an integrated step down switching regulator which has all necessary systems required for making a cost effective and reliable switching regulator circuit.
3. The IC is available in MSOP-8, LLp-8 packages and has a lot of  built in  features like thermal shut down, under voltage lock out, duty cycle limiting, current limiting etc.
4. The output voltage of this regulator can be adjusted using the resistor R3 and R4. 
5. OR the given values of R3 and R4 in the circuit diagram, the output voltage will be 10V.
6. he equation governing the output voltage is Vout = 2.5 x (R3+R4)/R4. Resistor R1 sets the switch on time and C4 is the boost boot strap capacitor.
7. Resistor R2 determines the variation of OFF time and C3 is a decoupling capacitor.

    NOTES:

• The supply voltage can be anything between 12 to 72V DC.
• Output voltage can be adjusted using R3 and R4.
• C1  and C5 are polyester capacitors.
• C1 and C2 must be rated at least 100V.
• R5 and C5 forms a filter network.
• The output current limit of LM5007 is 700mA.

3 INPUT MICROPHONE PREAMPLIFIRE

1. The circuit given here is of a three input mic mixer cum preamplifier using the IC LM348. The LM348 is a high gain, internally compensated quad operational amplifier with a class AB output stage.
2. The IC has very low input supply current drain (0.6mA/ opamp) and operates from a dual power supply.
3. Out of the four op-amps inside the IC LM348, IC1a, IC1b and IC1c are wired as non inverting amplifiers and they serve as the input amplifiers for the corresponding mic channels. 
4. The output of these three amplifiers are tied together and connected to the inverting input of the IC1a which is wired as an inverting amplifier.IC1a mixes the signals from each channel and also works as the output stage.
   
   
   
   
   
   
   
   
   NOTES:
   

   • Assemble the circuit on a good quality PCB.
   • Use +12/-12V DC dual supply for powering the circuit.
   • The power supply must be well regulated and filtered.
   • POT R5 to R7 can b e used for adjusting the gain of individual channels.

   
   
   
   

STEREO PREAMPLIFIER WITH TONE CONTROL

1. Here is the circuit diagram of an excellent stereo preamplifier with tone control using the IC TDA1524 from Phillips.
2. The IC requires very few external components, has very low noise and has a wide power supply voltage range.
3. POTs R1 to R4 can be used for controlling the volume, balance, bass and treble respectively.
   
4. 
   
   LED is D1 is a power ON indicator and R1o is its current limiting resistor.

   
   

   
   

   
   

   
   

   NOTES:
   

   • Assemble the circuit on a good quality PCB.
   • Switch S2 is the ON/OFF switch.
   • Swich S1 can be used to select linear or contour mode.
   • Supply voltage can be anything between 8 to 16V .Here I used 12V DC.

   
   

   
   

DARK DETECTOR

1. The dark detector circuit shown here can be used to produce an audible alarm when the light inside a room goes OFF.
2. The circuit is build around timer IC NE555.A general purpose LDR is used for sensing the light. 
3.  When proper light is falling on the LDR its resistance is very low.
4. When there is no light the LDR resistance increases.
5.   At this time the IC is triggered and drives the buzzer to produce an alarm sound.
6.  If a transistor and relay is connected at the output (pin3) of IC1 instead of the buzzer, electrical appliances can be switched according to the light.
   
   
   
   
   
   
   NOTES:
   

   • The LDR ,R4 can be any general purpose LDR.
   • The circuit must be assembled on  a good quality PCB or  common board.
   • The circuit can be powered from a 9V PP3 battery.
   • The POT,R3 can be sued as a volume controller.
   • Mount the IC1 on a holder.It will make replacements easy.

   
   

PARKING SENSOR CIRCUIT

1. This simple circuit can be used as an aid for sensing the distance between the rear bumper of the car and any obstacle behind the car. The distance can be understood from the combination of the LEDs (D5 to D7) glowing. At 25cm D7 will glow, at 20 cm D7&D6 will glow and at 5cm D7, D6 and D5 will glow. When the obstacle is beyond 25 cm none of the above LEDs will glow.
2.  Two ICs are used in the circuit. The IC1 (NE555) is wired as an astable multivibrator for driving the IR Diode D1 to emit IR pulses. The operating frequency of the transmitter is set to be 120Hz.
3.  The IR pulses transmitted by D1 will be reflected by the obstacle and received by the D2 (IR photo diode).The received signal will be amplified by IC2a.The peak of the amplified signal will be detected by the diode D4 and capacitor C4.R5 and R6 compensates the forward voltage drop of D4.The output voltage of the peak detector will be proportional to the distance between car’s bumper and obstacle.
4. The output of peak detector is given to the inputs of the other three comparators IC2b,IC2c and IC2d inside the IC2(LM324).The comparators switch the status LEDs according to the input voltage their inverting inputs and reference voltages at their non inverting inputs. Resistances R7 to R10 are used to set the reference voltages for the comparators.
   
   

   
   

   
   

   NOTES:
   

   • Assemble the circuit on a good quality PCB or common board.
   • The D1 & D2 must be mounted close (~2cm) to each other, looking in same direction.
   • The D1 can be a general purpose IR LED.
   • The D2 can be general purpose IR photo diode with sun filter.
   • The transmitter as well as receiver can be powered from the car battery.
   • For proper working of the circuit, some trial and error is needed with the position of D1 and D2 on the dash board.
   • All capacitors must be rated 25V.
   • The ICs must be mounted on holders.

   
   

100 WATT INVERTER CIRCUIT

1. Here is a 100 Watt inverter circuit using minimum number of components.I think it is quite difficult to make a decent one like this with further less components.Here we use CD 4047 IC from Texas Instruments for generating the 100 Hz  pulses  and four 2N3055 transistors for driving the load
2. The IC1 Cd4047 wired as an astable multivibrator produces two 180 degree out of phase 100 Hz pulse trains.
3. These pulse trains are  preamplifed by the two TIP122 transistors.The out puts of the TIP 122 transistors are amplified by four 2N 3055 transistors (two transistors for each half cycle) to drive the inverter transformer.
4. The 220V AC will be available at the secondary of the transformer.Nothing complex just the elementary inverter principle and the circuit works great for small loads like a few bulbs or fans.If you need just a low cost inverter in the region of 100 W,then this is the best.

     NOTES:

• A 12 V car battery can be used as the 12V source.
• Use the POT R1 to set the output frequency to50Hz.
• For the transformer get a 9-0-9 V , 10A step down transformer.But here the 9-0-9 V winding will be the primary and 220V winding will be the secondary.
• If you could not get a 10A rated transformer , don’t worry a 5A one will be just enough. But the allowed out put power will be reduced to 60W.
• Use a 10 A fuse in series with the battery as shown in circuit.
• Mount the IC on an IC holder.
• Remember,this circuit is nothing when compared to advanced PWM inverters.This is a low cost circuit meant for low scale applications.

     DESING TIPS:

• The maximum allowed output power of an inverter depends on two factors.The maximum current rating of the transformer primary and the current rating of the driving transistors.
• For example ,to get a 100 Watt output using 12 V car battery the primary current will be ~8A ,(100/12) because P=VxI.So the primary of transformer must be rated above 8A.
• Also here ,each final driver transistors must be rated above 4A. Here two will be conducting parallel in each half cycle, so I=8/2 = 4A .
   
  
  

  
  
   

TELEPHONE IN USE INDICATOR

1. Here is a simple circuit that can be used as a telephone status indicator. When the telephone is in use (off hook) the transistor Q1 switches ON making the red LED D2 glow.
2. When the telephone is not in use (on hook) the Q1 turns OFF and Q2 turns ON. 
3. This makes the red LED D2 off and green LED D3 ON.
4. The circuit is powered from the phone line itself and no external power supply is required.
   
   
   
   
   
   
   NOTES:
   

   • The circuit can be assembled on a general purpose PCB.
   • IF 2A ampere bridge is not available, make one using diodes like 1N4007.
   • Note that some countries prohibit people from connecting other devices to the phone line.

AIR CRAFT WARNING LIGHT CIRCUIT

1. Here is low cost circuit that can be used for implementing a warning light on the top of tall structures as a warning for low flying aircrafts.
2. Usually such lights are just stay glow type .Here our light is a flashing type, and surely this will draw more attention and of course add more safety.
3. When the AC mains is switched on the bulb will get supply and it will glow.
4. When the bulb glows the LDR adjacent to it gets illuminated and it’s resistance drops.This will increase the voltage drop at the base of transistor Q1 and it goes on.When Q1 is on the relay is activated and trips the contacts to make the bulb off.Now the LDR resistance increases and the voltage drop across base of Q1 decreases to make it off.
5. The relay will be de-energized and the bulb glows.This cycle repeats to produce a continuous flashing of the bulb.
6. Since the capacitor C1 is connected across the relay the relay will remain activated for some more time even after the transistor Q1 is OFF,making the bulb to stay off for some more time.

     NOTES:

• The LDR should be mounted at some place near to the bulb so that when bulb glows the light falls on the LDR.
• Set up the circuit as said above and power up.Then adjust the POT R2 so that the bulb starts flashing.Done!The circuit is ready.
• Some parts of the circuit are live with potential shock hazard.Be careful!.
• Bulb of any Watts can be used as load provided that a relay with suitable power rating is used.
• All capacitors are electrolytic and must be rated 25Volts.

BATTERY ELIMINATOR CIRCUITS

1. Here is the circuit diagram of a battery eliminator circuit that can be used as a replacement for 9V PP3 batteries.
2. The circuit given here can be used to power any device that operates from a 9V battery.
3. The transformer T1 steps down the mains voltage and bridge D1 performs the job of rectification.
4. Capacitor C1 is a filter. IC LM317T is the regulator here.
5.  The value of R1, R2 and R3 are so selected that the output voltage of IC1 will be steady 9 volts.
   

      NOTES:

• Assemble the circuit on a good quality PCB.
• Transformer T1 can be a 230V primary, 9V secondary, 1.5A step down transformer.
• If 1A Bridge is not available, then make one using four 1N 4007 diodes.
• Do not connect loads that consume more than 1.5A to this circuit.
• A heat sink is recommended for IC1.

CONTECT LESS TELEPHONE RINGER CIRCUIT

1. The contact less telephone ringer circuit can produce a ring as well as a visual indication when a call comes.
2. The main advantage is that since there is no direct contact between the phone line and the circuit there is no chance for a loading or disturbance in the telephone line.
3. When the telephone rings 60 Hz AC signal is generated which produces a proportional magnetic field around the telephone lines.
4.  These magnetic field will be picked up by the coil L1 due to electromagnetic induction.
5.  A proportional voltage is developed across L1 and it will bias transistor Q1 to ON.
6. This results in the conduction of transistors Q2,Q3 andQ4.The buzzer will ring and the LED will glow.
7. The switch S1 acts as an ON/OFF switch.

   
   

   
   

   
   

   
   

   NOTES:

   • For L1 make 50 close turns of 28 SWG enameled copper wire on any of the two telephone wires.Connect one end of the coil to base of Q1 and leave other end free.
   • If the circuit not works by try by changing the end of the L1 connected to base of Q1.
   • A 9V transistor radio battery can be used as the power source.
   • Assemble the circuit on a good quality PCB or common board.
   • Use of this type or any other devices other than the allowed telephones and devices with the telephone line may be a law violation in some nations.Check it properly before trying.

   
   
   
   

   
   
    

VHF FIELD STRENGTH METER

1. This is a simple and low cost wide band VHF field strength meter.
2. The field strength is measured by converting the radio signal to DC and measuring it.
3.  The RF signal will be picked up by the coil and rectified by the diode D1.Even a very small DC voltage is sufficient to alter the biasing of FET and it will be reflected in the meter as an indication of the presence of a radio signal.
   
4. he meter can be calibrated by adjusting the preset R2 to make meter M1 read ZERO in the absence of any radio signal.
5. This circuit is not very sensitive, but can sense radio signals from hand held FM transmitters up to a distance of few meters( ideal for theoretical demonstrations).

     NOTES:

• The circuit can be assembled on a general purpose PCB.
• Use a 9V PP3 battery for powering the circuit.
• Use a 250uA FSD current meter for M1.Using a lower FSD meter will improve sensitivity.
• The coil L1 can be made by making 6 turns of 20 SWG enameled copper wire on a ¼ inch plastic former.
• The antenna can be a telescopic whip antenna.

SELECTIVE TIMER ALARM

1.  A timer circuit using IC 4060 is given here. The IC 4060 is a 14 stage binary counter with a built-in oscillator.
2. R2, R7, C1 are the components that determine the frequency of the oscillator and the outputs will become high one after other and only one at a time.
3.  The last five outputs are only used here. The high pulses from the outputs are used to trigger the NE555 IC.
4.  Here NE555 is wired as a monostable multivibrator. The buzzer will produce the alarm when the output of IC2 goes high.
5.  The duration of the alarm depends on the components C3 and R5.The duration can be adjusted by varying the value of C3.
6.  The alarm will automatically turn OFF after the predetermined time. The trigger pin of IC2 will be normally positive.
7.  When the Q1 is forward biased by the positive pulse at its base from IC1, the capacitor C2 becomes charged and reduces the voltage at trigger pin of IC2.This triggers the IC.When the capacitor is fully charged the pin 2 becomes again positive.
8.  The maximum duration from timer IC 4060 will be at pin 3. The times decrease by half in the pins 2, 3, 15, and 13 respectively. The timer duration can be varied by varying the capacitor C1.

       NOTES:

• Use 6V DC for powering the circuit.
• Assemble the circuit on a good quality PCB.
• Mount the ICs on holders.
• The switch S2 can be a single pole five throw rotary switch.
• The switch S1 can be a push button switch.
• S1 is used to reset the timer.
• S2 is used to select the alarm time.
• R7 can be used for the fine adjustment of alarm time.

SIGNAL TRACER CIRCUIT

1. A high gain amplifier circuit that can be operated from a battery pack of 6 or 9 volt battery pack is shown here.
2. The IC1 uA 741 is wired as a high gain non-inverting amplifier and its output is amplified by a pair of complementary transistors (Q1 & Q2) to drive the speaker.The negative feedback from the common emitter junction of the two transistor stabilizes the gain of the circuit.
3. The resulting audio output is sufficient to serve as a signal tracer.
   
   
    

       NOTES:

• Assemble the circuit on a  good quality PCB or  common board .
• The POT R6 can be used as a volume controller.
• The circuit can be powered from a 6 or 9V DC battery pack.
• The IC1 must be mounted an an IC base.
• All capacitors must be rated at least 15V.

MIDIUM POWER FM TRANSMITTER CIRCUIT

1. This is the circuit diagram of a moderate power FM transmitter circuit employing two transistors.The voice signals picked by the microphone will be amplified by the transistor Q1.
2.  The second transistor is wired as an oscillator operating in the FM band.
3.  The output of T1 is given to the base of T2.T2 performs the modulation also.
4.  The tank circuit comprising of components L1 and C6 determines the frequency of the signal, and can be varied by adjusting C6.The capacitor C7 couples the FM signal to the antenna.
   
   

        NOTES:

• You can assemble the circuit on a general purpose PCB.
• The circuit can be powered from a9V PP3 battery.
• The Antenna A1 can be a 1M long wire.
• The inductor L1 can be made by making 6 turns of 0.8mm enameled copper wire on a 5.5mm diameter/4.5mm length plastic former.
• With a matching antenna and proper tuning this transmitter can have range upto 100meters.

SIMPLEST FM TRANSMITTER

1. Here is the circuit diagram of the simplest FM transmitter using a transistor.
2. Great performance or range is not guarenteed here, because this is an elementary design.
3. General purpose radio frequency transistor BF 494 (Q1) is used here for obtaining FM modulation.
4. A condenser mic is used here to pickup the sound.
5. The condenser mic converts the sound to electrical variations and this variations are fed to the base of Q1 , which performs the amplification as well as modulation.
6. The capacitor  C2   and L1 determines the frequency of transmission.The circuit can be powered from a 9V transistor radio battery.

 

      NOTES:

• The coil L1 can be made by winding 8 turns of 1mm thick enamel coated copper wire on a ball pen refill.  The coil should be tapped  at the  center for connecting the antenna.
• A 30 cm wire can be used as an antenna.
• Remember! This circuit is an elementary circuit.No good performance or range is not guaranteed.Ideal for demo applications only.I got only 8 meter range with some decent sound quality.
• Battery is strictly recommended because mains powered supply may induce additional noise.

RADIO COLLAR TRANSMITTER

1. This is the circuit diagram of a radio transmitter suitable for fitting on radio collars.
2. The circuit transmits a pulse in the FM between band 88MHz to 105Mhz , which can be adjusted.
3. IC Ne 555 is wired as an astable multivibrator for producing the tone.L1 ,C3 and Q1 forms the modulator.
4. Q2 performs the final power amplification. 
5. For the inductor make 5 turns of .5 mm dia insulated copper wire on a standard ball pen refill.
6. Remove the refill and make a tap at the center of coil.
7. 
   
   To vary transmission frequency experiment with number of turns.
8. 
   
    Carefull! what ever may be the no of turns the tap must be at center.Use a 50 Cm long insulated copper wire as antenna.
   

   
   

   
   

   
   

   
   

   PART LIST:
   

   • R1…………………………………. 10K

   • R2 …………………………………1 M Ohm

   • R3 ………………………………….330 Ohm

   • R4 …………………………………..1 M Ohm

   • R5……………………………………. 330 Ohm

   • R6 ……………………………………200 Ohm POT

   • C1 ……………………………………..0.1 uF Ceramic

   • C2…………………………………….. 0.01 uF Ceramic

   • C3…………………………………….. 13 pF Ceramic

   • C4 ,C5, C6,C5 ……………………..0.01 uF Ceramic

   • Q1 ,Q2 ………………………………..2N4392 JFET

   • D1 ……………………………………….1N 914 Diode

   • IC 1……………………………………… NE 555

   
   
    
    

   

SPEECH AMPLIFIER CIRCUIT

1. This circuit given here can be housed in the box containing the speaker to form a handy microphone amplifier.
2. The device can be used by teachers,guides,lecturers etc for speaking in a crowdy or noisy environment.
3.  The circuit is designed base on the audio power amplifier IC TDA 7052.
4.  The IC can deliver a maximum power output of 1.2 W at a 6V supply.
5. The audio signal from the microphone is pre amplified by the amplifier based on Q1 (BC 547) and give to the input of IC1 (pin 2).
6.  The POTR5  acts as a volume control.
7.  The capacitor C3 is used to bye pass the upper frequencies in order to avoid the Larsen’s effect(the microphone picking up speaker output to cause howls).
   
   
   
   
   
   
   
   
   NOTES:
   

   • Use a 8 Ohm speaker or two 4 Ohm speakers in series as load.
   • Assemble the circuit on a good quality PCB or common board.
   • A 6V SMF battery is my choice for powering the circuit.
   • Switch S1 can be used as a ON/OFF switch.

   
   

HI-FI DX BASS CIRCUIT

1. The circuit that designed is a passive one but you can make it an active one by adding a pre amp at the output.
2. The first stage acts as a main tone stage. It balances the bass and the treble. The 0.01 cap is for high frequency while the 0.22uF cap is for low frequency.
3.  The second stage is for sound compression.
4.  he caps works the same as at the first stage only that they are there to start the sound compression that is received from the input stage.
5.  The 2.2k resistor delays the sound thereby multiplying the compression.
6.  The 10k variable resistor is there used to tune the compression depending on the frequency of the speaker. If you are using 4 to 6 inches hi-fi speakers, I advise you to keep the 10k variable resistor at 0 ohm.
7. The circuit is not copyrighted and you can change it to suit your requirement. All I ask is to be posting the updates of the circuit design on the site.
   
   
   
   
   
   
   
   
   NOTES:
   

   • Assemble the circuit on a good quality PCB.
   • This circuit does not require a power supply.
   • POT R6 is for volume control.
   • Switch S1 can be a slide switch and it is the DX Bass switch.

   
   
    
   
   

FM TRACKING TRANSMITTER

1. The circuit presented her will transmit a audio tone in the FM  band.
2. The circuit can be used as a tracking signal transmitter or a remote control transmitter.
   
3. The circuit uses only easily available components and any one can build this.The transmitter has a range of 100m @ 9V supply, with a matching antenna.
   
4. The NE555 timer (IC1) is used for producing the audio tone.
5. The first JFET(Q1) is wired as a Hartley oscillator which is frequency modulated by the audio tone.The second(Q2) JFET is wired as a buffer to isolate the oscillator based on Q1 from the antenna.
   
6. The diode D1 is used as a varactor here.The diode is reverse biased by the ramping voltage produced at the pin 6&2 of the IC1.
7. This results in the change of junction capacitance of reverse biased diode , which in turn alters the frequency of the oscillator to attain the frequency modulation.

          NOTES:

• The inductor L1 can be made by winding 5 turns of  18 SWG enameled copper wire on a 3/8 inch long, 3/16 inch diameter plastic tube .The coil must be tapped at the center.
• The antenna can be a 20cm long wire.
• The circuit can be powered from a 9V battery.
• POT R6 can be used to adjust the transmission power.

INFRARED MOTION DETECTOR CIRCUIT

1. Here is the circuit diagram of an infrared motion detector that can be used to sense intrusions.
2. 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.
3. The circuit uses this principle to sense the motion.
4. The IC1 (NE 555)  is wired as an astable multivibrator .
5. 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.
6. At normal condition ie; when there is no intrusion the output pin (7) of IC2 will be low.
7. 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.
8. 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.

REMOTE CONTROLLED APPLIANCE SWITCH

1. Here is a versatile remote controlled appliance switch that can ON or OFF any appliance connected to it using a TV remote.
2. IR remote sensor IC TSOP 1738 is used for receiving the signal.
3.   Normally when no signal is falling on IC3 the output of it will be high.
   
4. This makes Q1 OFF.When a signal of 38 KHz from the TV remote falls on the IC3 its output goes low.
5.  This makes Q1 conduct and a negative pulse is obtained at pin 2 of IC 1 NE 555.
6.  Due to this IC1 wired as a monostable multivibrator produces a 4 Sec long high signal at its out put.
7.  This high out put is the clock for IC 2 which is wired as a Flipflop and of , its two outputs pin 3goes low and pin 2 goes high.
8. The high output at pin 2 is amplified to drive the relay .For the next signal the outputs of IC2 toggles state.
9.   Result, we get a relay toggling on each press on the remote.Any appliance connected to this circuit can be switched ON or OFF.

          NOTES:

•  Before wiring the circuit make sure that the carrier frequency of theTV remote you have is 38 kHz.For that wire the sensor part only ,point yourremote to the TSOP1738 and press any switch.If out put of TSOP1738 goeslow then OK, your remote is of 38Khz type.Nothing to worry almost all TVremote are of this type.

•   You can use any switch  of the remote because for any switch the code only changes,the carrier frequency remains same.We need this carrier frequency only.

•   Assemble the circuit on a good quality PCB or common board.

•  The appliance can be connected through NO or NC and C contacts of the relay .

• Use a regulated 6V power supply for the circuit.