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Tuesday, June 21, 2011

Power Saving Led Lamp

Power saving LED lamp from your scrap box.
This circuit is designed by Mr Seetharaman Subramanian and we are very glad to publish it here. In this article he is showing a method to convert a broken/defunct CFL into a LED based power saving light.
The  is just a LED lamp circuit that can be operated from the mains voltage. A string of five LED is driven using a capacitive transformer less power supply. In the circuit 0.47uF/400V Polyester capacitor C1 reduces the mains voltage. R1 is a bleeder resistor which drains the stored charge from C1 when the AC input is switched OFF. Resistors R2 and R3 limits the inrush of current when the circuit is switched ON. Diodes D1 to D4 forms a bridge rectifier that rectifies the reduced AC voltage and C2 acts as a filter capacitor. Finally Zener diode D1 provides regulation and the LEDs are driven.
source: www.circuitstoday.com

Tester Voltage Circuit

 
This circuit can be used to test whether mains voltage is present or not without having electric contact with mains line. The CMOS IC CD4033 is the heart of this circuit. The CD4033 consists of a 5 stage decade Johnson counter and an output decoder for converting the Johnson code to a 7 segment decoded output for driving 7 segment LED display. A 10cm long insulated copper wire connected to the clock pin (pin1) of the IC serves as the sensor. The sensor wire has to be placed in the vicinity of the mains wire to be tested. When there is no voltage in the mains line, no voltage will be induced in the sensor wire and the display will show a random digit. When there is voltage in the mains line, a small voltage will be induced in the sensor wire due to electromagnetic induction and this voltage is sufficient enough to clock the CMOS IC CD4033. Now the display will count from zero to nine and repeat.
Circuit diagram.
Notes.
The circuit can be assembled on a Vero board.
Use 9V PP3 battery for powering the circuit.
Use a 10cm insulated wire as the sensor.
The IC must be mounted on a holder.
Switch S1 can be a miniature ON/OFF switch

source: http://www.circuitstoday.com/

Lampu Flash LM317

Here is a very useful lamp flasher circuit using the famous adjustable voltage regulator IC LM317T. LM317 can source up to 1A of current and so up to 12W lamps can be used with this flasher. Such a circuit finds huge application in automobiles. The frequency of the flashing depends on the value of resistors R1 to R3 and capacitors C2 to C4.With the given values; the flashing rate is around 5 flashes per second.
Circuit diagram.
Notes.
The circuit can be assembled on a Vero board.
Use 12V DC for powering the circuit.
Use a proper heat sink with the IC1

Read more: http://www.circuitstoday.com/lamp-flasher-using-lm317#ixzz1PqKIZZXd

Dancing Light

 
Here is a simple dancing light circuit based on NE555 (IC1) & CD4017 (IC2) .The IC1 is wired as an astable multivibrator to provide the clock pulses for the CD4017.For each clock pulse receiving at the clock input (pin14) of IC CD4017, the outputs Q0 to Q9 (refer pin diagram of CD 401) becomes high one by one alternatively.The LEDs connected to these pins glow in the same fashion to give a dancing effect.The speed of the dancing LEDs depend on the frequency of the clock pulses generated by the IC1.
Circuit diagram with Parts list.
Notes.
Assemble the circuit on a good quality PCB or common board.
The ICs must be mounted on holders.
The speed of the dancing LEDs can be adjusted by varying POT R2.
The capacitor C1 must be rated 15V.
Using different color LEDs could produce a better visual effect

source: http://www.circuitstoday.com

Digital Dice Light


This is a simple and easy to construct digital dice circuit. The circuit is based on a single IC, CD4060B.The dice consists of six LEDs marked D1 to D6.The number of LEDs glowing indicates the numeral.
The heart of this circuit is 14 stage binary ripple counter IC CD4060B.The IC also has a built-in oscillator. The oscillator output (here 2 KHz) is used to clock the binary ripple counter. The counter increments by one in its natural count sequence each time it is clocked. The oscillator in initially inhibited as long as the pushbutton switch S2 is not pressed. The counter outputs will be in logic zero state and all the six LEDs will be ON.As the push button S2 is pressed, oscillator is enabled and the counter starts counting. The counter outputs (pin 4, 5 & 7) changes from 000 to 101 and then resets to 000 to repeat the sequence. After 101 the counter does not advances to 110 because of R3, D7 & D8.When the counter just advances from 101 to 110 the diodes D7 & D8 become reverse biased and makes the reset pin (pin 12) high to reset the counter.
The counter counts as long as the push button switch S2 is pressed. Also the micro buzzer will sound as long as the IC is counting. When the push button switch S2 is released, the counting is stopped and holds the existing state to represent the random number.Circuit diagram with Parts list.
Notes.
Switch S1 is the ON/OFF switch.Switch S2 can be a push button switch.Buzzer K1 is a piezo buzzer.The circuit can be powered from a 9V PP3 battery.The IC must be mounted on a holde
source: http://www.circuitstoday.com

Monday, June 20, 2011

Battere Charger 24 volt


This lead acid battere charger circuit is designed in response to a request from
Mr.Devdas .C. His requirement was a circuit to charge two 12V/7AH lead acid batteries in
series.Anyway he did not mentioned the no of cells per  each 12V battery. The no of
cells/battery is also an important parameter and here I designed the circuit assuming 
each 12V battery containing 6 cells. When two batteries are connected in series, the
voltage will add up and the current capacity remains same. So two 12V/7AH batteries
connected in series can be considered as a 24V/7AH battery.
The circuit given here is a current limited lead acid battery charger built around the
famous variable voltage regulator IC LM 317. The charging current depends on the value
of resistor R2 and here it is set to be 700mA. Resistor R3 and POT R4 determines the
charging voltage. Transformer T1 steps down the mains voltage and bridge D1 does the job
of rectification. C1 is the filter capacitor. Diode D1 prevents the reverse flow of
current from the battery when charger is switched OFF or when mains power is not available.
Notes.
Assemble the circuit on a good quality PCB.
T1 can be a 230V primary, 35V/3A secondary step down transformer.
If 3A Bridge is not available, make one using four 1N5003 diodes.
LM317 must be fitted with a heat sink.
R2 = 0.85 ohm  is not a standard value. You can obtain it by combining a 6.2 ohm and 1
ohm resistors in parallel.
F1 can be a 2A fuse.
To setup the charging voltage, power ON  the charger and hook up a voltmeter across the
output terminals and adjust R4 to make the voltmeter read 28V. Now the charger is ready
and you can connect the batteries.
This charger is specifically designed for two 12V/7AH/6 cell lead acid batteries  in
series OR a  24V/7AH/12 cell lead acid battery.

Read more: http://www.circuitstoday.com/24v-lead-acid-battery-charger-circuit#ixzz1Pls7sC8t

Skema Bel Musik


This circuit produces a musical tone whenever someone touches the touch point designated as TP in the circuit. The circuit works from two AA cells and produces enough sound.
The circuit uses IC UM 3481 commonly used in musical circuits. The IC contains a ROM with 512 musical notes, tone generator, rhythm generator, modulator, run off control, oscillators, frequency divider and preamplifiers,.  So a very few number of components is  required for this circuit.C1 and R1 act as  the timing components for  the built in oscillator. The transistor Q1 is used for driving the loud speaker. The base of the transistor Q2 is used as the touch point to trigger the musical bell.
Notes.
The circuit can be assembled on a general purpose PCB.
Use two AA cells in series for powering the circuit.
The speaker can be 2 W, 8 Ohm.
source circuitstoday.com

Sirine 2 Transistor



Here is the circuit diagram of a simple two transistor alarm circuit that can be operated from a 9V PP3 battery. Here the two transistors are wired to form an oscillator whose frequency increases when switch S2 is pressed and decreases when S2 is released. In order to attain this the base of Q1 is biased from an RC circuit comprising of R2 and C1.When S2 is pressed C1 is charged through the resistor R2.As the voltage across the C1 increases the time constant decreases and this results in an increases in the frequency. When S2 is released capacitor discharges and the frequency of the tone decreases. The sound heard from the speaker will be almost like that of a siren.
Notes.
The circuit can be assembled on a Vero board.
Use a 9V PP3 battery for powering the circuit.
Switch S2 can be a miniature push button switch.
The type no of transistors are not very significant here

Read more: http://www.circuitstoday.com/two-transistor-siren#ixzz1PiqIUanY

UP DOWN counter circuit

UP DOWN counter circuit
    
This is the circuit diagram of a very simple up down counter that can be used of a large number of applications. The circuit is based on the IC CD40110BE which is a CMOS decade up/down counter. For ICs are used here. Common cathode seven segment display is connected to the 7-segment output of each IC.Display connected to the IC1 represents the lowest number and display connected to IC4 represents the largest number. Synchronous counting is achieved by connecting BORROW and CARRY pins of the preceding stage IC to the CLK DOWN and CLK UP of the next stage IC. For UP counting trigger pulse must be given to the pin7 of IC1 and for down counting trigger pulse must be given to the pin9 of IC1.The RESET pins of all IC are shorted and they have to be connected to ground during normal operation. Connecting the RESET pins to positive supply using the  switch S1 resets the counter.
Notes.
The circuit can be powered from a 9V PP3 battery.
All 7 segment displays must be common cathode type.
Resistors R1 to R28 must be 680 Ohm ones.
R29 and R30 can be 10K ones.
Switch S1 can be  a SPDT switch

Read more: http://www.circuitstoday.com/up-down-counter-circuit#ixzz1PiluR9AT

Sunday, June 19, 2011

Display 0-9 circuit

Static 0 to 9 display
    
The circuit shown here is of a simple 0 to 9 display that can be employed in a lot of applications. The circuit is based on asynchronous decade counter 7490(IC2), a 7 segment display (D1), and a seven segment decoder/driver IC 7446 (IC1).
The seven segment display consists of 7 LEDs labelled ‘a’ through ‘g’. By forward biasing different LEDs, we can display the digits 0 through 9. Seven segment displays are of two types, common cathode and common anode. In common anode type anodes of all the seven LEDs are tied together, while in common cathode type all cathodes are tied together. The seven segment display used here is a common anode type .Resistor R1 to R7 are current limiting resistors. IC 7446 is a decoder/driver IC used to drive the seven segment display.
Working of this circuit is very simple. For every clock pulse the BCD output of the IC2 (7490) will advance by one bit. The IC1 (7446) will decode this BCD output to corresponding the seven segment form and will drive the display to indicate the corresponding digit.
Notes.
The circuit can be assembled on a perf board.
Use 5V DC for powering the circuit.
The clock can be given to the pin 14 of IC2.
D1 must be a seven segment common anode display.
All ICs must be mounted on holders

Read more: http://www.circuitstoday.com/static-0-to-9-display#ixzz1PinPUJKV

15 Watt Audio Amplifier


The circuit shown here is of a simple Class-B audio amplifier based on opamp TL082,
transistors TIP141 and TIP142. LM833 is a dual opamp with high slew rate and low
distortion particularly designed for audio applications. This audio amplifier circuit
can deliver 15 watt audio output into an 8 ohm speaker at +12/-12V DC dual supply.
Both opamps in the IC are used here. IC1a is wired as a buffer and capacitor C3 does the
job of input DC decoupling. Ic1b is wired in the inverting mode and it provides negative
feedback. Complementary power transistors TIP41 and TIP42 are wired in the Class B push
pull scheme and they drives the loud speaker. Diode D1 provides 0.7V bias voltage for
the push pull pair and capacitor C2 protects the 0.7V bias voltage across D1 from heavy
voltage swings at the IC1b’s output.
Notes :
The audio amplifier circuit must be assembled on a good quality PCB.
Use a holder for mounting IC1.
Use a +12/-12V dual supply for powering the amplifier.
Potentiometer R2 can be used as a volume control.
Raising the power supply voltage will increase the output power. Anyway note the
following points.
TIP42 and 41 can handle only up to 6A.
Maximum supply voltage IC1 can handle is +16/-16 V DC
Read more: http://www.circuitstoday.com/15w-class-b-audio-amplifier#ixzz1PgCb5tTk

Switching regulator dan Step Down circuit


Switching regulator .
   
Switching regulators work by drawing small amounts of energy from the input source and transferring it step by step to the output. This task is attained by using an electronic switch (operating at a predetermined frequency) which works like a gate between the input energy source and the output. This gate controls the amount of charge that is transferred to the output load. The output voltage of the switching regulator depends on how much time the switch is maintained closed. If the OFF time of switch is long then less energy will be transferred to the output load and so the average output voltage will a be low. If the OFF time of switch is short then more energy will be transferred to the output load which results in a better average output voltage.The schematic of a basic switching regulator is shown below.
Schematic of a simplified switching regulator circuit
When switch S1 is closed capacitor Cout is charged and when switch S1 is open the Cout discharges through the load. The duty cycle of the S1 determines how much energy is transferred to the output load. In simple words the capacitor Cout serves as a filter which converts the pulse waveform from the switch in to a steady voltage. The output voltage will be always a function of the input voltage and the duty cycle of the switch.
Schematic of a practical switching regulator
The schematic of a practical switching regulator is shown above. This circuit has two additional components, a Schottky diode D1 and an inductor L1. These two components are present in almost all switching regulator circuits and they drastically improves the performance of the circuit. Let us see how the diode and inductor improves the performance of the regulator circuit.
When switch S1 is closed the inductor L1 opposes the rising current by creating an opposing electromagnetic field and this makes the diode D1 reverse biased and it behaves like an open switch. When switch S1 is made open the electromagnetic field that was induced in the inductor L1 will be discharging and this creates a current in the reverse polarity. This makes the diode D1 forward biased and it will remain in the conducting stage until the field in the inductor becomes zero. In simple words this action is similar to the charging and discharging of the output capacitor. Thus the combined effect of the inductor and diode improves the filtering capability of the output capacitor and so the circuit efficiency is improved.
uA78S40 based switching regulators.
Here are two switching voltage regulator circuits using uA78S40 IC from On Semiconductors. The first one is a step down converter while the second one is an inverting converter.
uA78S40 is a switching regulator IC that can be used for a variety of applications. The uA78S40 is an integrated switching regulator circuit which has built in circuitries for voltage reference with temperature compensation, oscillator with duty cycle control, high capacity switching element, an independent operational amplifier and independent diode. When voltages excess of 40V or output currents excess of 1.5A are required external switching transistors must be used. The features of uA78S40 include wide temperature range, adjustable output voltage (from 1.5V to 40V), peak output current of 1.5A, 80dB load regulation, 80dB line regulation, wide supply voltage range ( from 2.5V to 40V), very low standby current etc. The applications of this IC include step up converters, step down converters, inverting converters etc. The uA78S40 is available in a 16 pin DIP plastic package.

Step down converter circuit.

    
Step down regulator using uA78S40
The circuit shown above is of a switching step down converter using uA78S40. The input voltage can be 25V DC and the output voltage is 5V @500mA. Ct is the timing capacitor for the internal oscillator while C3 is the input filter capacitor.C3 must be rated above 25V while C2 can be rated anything higher than 10V. The instantaneous output voltage (that is the voltage across output capacitor Cc) is fed back to the inverting input of the internal opamp using the resistor network comprising of R1 and R2. R2 and R1 can be used for setting the output voltage. Using the external rectifier diode D1 improves the overall efficiency of the circuit. If you need to use the internal diode of the IC instead of D1 then omit D1 and restore the track shown dotted.

source  www.circuitstoday.com

Dual Power Supply dan inverting convert circuit

Dual supply for this circuit.
   
A  +15V/-15V dual supply for powering this tone control circuit is shown below. Bridge D1 can be made using four 1N4007 diodes.  This supply is unregulated and its quite fine for this circuit. Anyway  if you need to have a regulated one please inform me.
Power supply for tone control circuit
Notes.
Circuit can be assembled on a vero board or perf boad. Any way a PCB is the best option.
Use +15/-15V DC dual supply for powering the circuit.
IC1 TL072 must be mounted on a holder.
By changing the value of R1 and R2 the voltage gain (Av) of the preamplifier stage can be changed

Read more: http://www.circuitstoday.com

Inverting converter circuit.
    
Inverting converter circuit using uA78S40
An inverting converter is a circuit which reverses the polarity of a given input voltage. For example if 5V DC is applied at the input of an inverting converter, the output voltage will be -5V DC. A 15V inverting converter circuit using uA78S40 is shown above. Ct (in the circuit C1) is the timing capacitor for the ICs internal oscillator, C3 is the input filter capacitor and C2 is the output filter capacitor. Both C2 and C3 must be rated at least 25V. Resistors R1 and R2 forms a feedback network which feed backs a portion of the output voltage to the non inverting input of the Ics internal comparator. R2 and R1 can be used to set the output voltage. Transistor Q1 is the external switching transistor. The collector terminals of the internal driver and switching transistors are shorted and connected to the base of the external switching transistor through resistor R3.

Notes.
uA78S40 must be mounted on a holder.
Peak output current of uA78S40 is 1.5A.
1N5822 is a 3A Schottky diode. Do not replace it with an ordinary PN junction diode.
Vout = 1.25 (1+ (R2/R1)) for step down converter.
Vout = (1.25R2) / (R1) for inverting converter.
Switching Regulator Vs Linear regulator.
The controlling element for a linear regulator is an active device ( either a BJT or FET) operating inside its active region.In a linear regulator the difference between the input voltage and output voltage is dissipated as heat by the controlling element. This reduces the power efficiency. The controlling element requires a larger heatsink .

For a switching regulator the controlling element which is an electronic switch (a transistor or thyristor) has only two states, either ON (completely conducting) or OFF (completely open). This means that no power is wasted across the switching element and this result in better power efficiency. A well designed switching regulator can have up to 85% efficiency. The controlling element requires a smaller heatsink.

Saturday, June 18, 2011

Tone control circuit

Tone control circuit
   
This is just another circuit designed by Mr. Seetharaman Subramanian and time it is a high quality passive tone control circuit that has an overall gain of around 25 with 20dB boost and cut. This circuit needs minimum number of components, is very cost effective and most of the components required can be found from you junk box. Even though an opamp which is an active element is used in the circuit, the tone control section is entirely passive and that’s why the circuit is named so.
The circuit consists of two parts. Firstly an op-amp based preamplifier stage and secondly a passive Baxandall tone control circuitry. The preamplifier stage is a non inverting amplifier based on TL072. R2 is the feedback resistor which together with resistor R1 sets the gain of this stage and with the stated values it is 23. Voltage gain in the non-inverting mode is expressed using the equation Av= 1+ (R2/R1). Value of R3 (Rin) is taken as approximately equal to the output impedance of TL072. C2 is the input DC decoupling capacitor and it also sets the low frequency cut off limit. R4 is the offset minimizing resistor which reduces the effect of output offset voltage on the output of the amplifier and its value is taken as approximately equal to R1||R2. The preamplifier stage is powered using +15/-15 dual supply. Capacitor C3 couples the preamplifier stage with the tone control stage.
The tone control stage is a passive Baxandall tone control circuit that can produce a 20dB cut or boost. POT R6 is used for controlling the bass while POT R9 can be used for controlling the treble. POT R10 serves as the volume controller while POT R11 can be used to adjust the balance. Resistor R8 provides some isolation between the bass control and treble control stages.
Passive Baxandall tone control circuit: Also known as James Network is a circuit for independently adjusting the bass and treble for high quality audio applications. The circuit is entirely based on passive components and the performance is very superior. In many older passive tone control circuits there was much interaction between the two controls and there was a great deal of asymmetry. Such problems are completely eliminated in Baxandall tone control circuit.
Seetharaman’s words about the circuit: Iam just enclosing you the TL072 (TL062 or 82 also can be used) passive tone control with 20dB boost and cut with a overall gain of around 25. you can also give an overall feedback if required, from output to TL072 inverting input through suitable resistance.

source   www.circuitstoday.com

IDO Regulator


The circuit shown above is of a practical LDO regulator circuit using IC LM2941 from National semiconductors. LM2941 is an integrated LDO voltage regulator IC whose output can be adjusted. The IC has many good features like thermal shutdown, transient protection, short circuit protection etc. The reverse polarity protection feature makes this IC very applicable in automotive applications. The output voltage can be adjusted from 5V to 20V and the dropout voltage is 0.5V at 1A output current.
In the circuit the voltage divider network comprising of R1 and R2 sets the output voltage. Capacitor C2 is the input filter which is very essential if the regulator circuitry is situated away from the rectifier+filter module. Capacitor C1 is the output filter while S1 is the ON/OFF switch. Resistor R3 is used to ensure the necessary 300mA pull up current which is necessary for proper shutdown when the switch S1 is made open.

Notes.
The circuit must be assembled on a good quality PCB.
A heat sink is required for application above few hundred milli amps.
Vout = 1.275 ((R1 + R2)/R1)
During calculation select R1=1K and solve for R2.
Selecting R1 = 1K will make the input bias current error of the adj pin negligible.
Reducing the value of C1 below 22uF will induce instabilities and also this capacitor must be placed as close as possible to the IC on the PCB.

Read more: http://www.circuitstoday.com/ldo-regulator#ixzz1PYuKlUfp

Night security light

Night security light
  
Here is a simple circuit switches on a light around 2 hours after midnight, the time at which most of the robberies taking place.
This simple circuit is build around a CMOS IC 4060 to obtain the required timing. During day time the LDR has low resistance and keeps the pin 12 of the IC1 high, preventing the IC1 from oscillating. When it is dark the LDR resistance becomes high and the pin 12 of IC1 becomes low and the IC starts oscillating, which indicated by the flashing of LED D3.The values of the timing components R1, R2, C4 are so selected that the out put pin3 of IC1 goes high after 8 hours. That means the high output drives the triac to switch on the lamp around 2’O clock. At morning, the LDR resistance drops and the pin 12 of IC1 goes high and stops the oscillation, making the lamp OFF. The switch S1 can be used to manually ON the lamp. The capacitor C2 prevents false triggering.
Notes.
Assemble the circuit on a good quality PCB or common board.
The LDR can be general purpose LDR.
The light sensitivity can be adjusted using the preset R6.
The IC1 must be mounted on an IC holder

Read more: http://www.circuitstoday.com/night-security-light#ixzz1PYwEomYK

Simple UPS

Simple UPS
  
This is the circuit diagram of a simple UPS that can deliver 12V unregulated and 5V regulated DC. The transformer T1 steps down the mains voltage to 12V AC and then the bridge B1 rectifies it. The rectified signal is smoothed by the capacitor C1.When the mains supply is available the battery will be charged via diode D3 and the regulator IC gets supply via diode D5. 12V and 5V DC will be available at the output terminals. When mains supply is not available the battery supplies current to the regulator IC and to the 12V DC terminal through diode D4.Also, the diode D3 blocks reverse flow of current during battery mode. Capacitors C2 and C3 acts as filters.
Notes.
Assemble the circuit on a good quality PCB.
The transformer T1 can be a 230V AC primary, 12V secondary,3A step-down transformer.
The bridge B1 can be a 2A bridge. If such a bridge is not available, make one using four 1N4007 diodes.
The capacitor C1 must be rated at least 25V

Read more: http://www.circuitstoday.com/simple-ups-construction#ixzz1PX9rSyOJ

Friday, June 17, 2011

Fuse with status indicator

Fuse with status indicator

   
Here is the circuit diagram of a fuse that has an automatic status indicator. This circuit can be added to circuit that operates from 12V DC. As long as the fuse is intact, the LED D3 will glow continuously and when the fuse blows off the LED will start and continue blinking.
The first part of the circuit includes an astable multivibrator built around transistors Q1 and Q2.The output of the multivibrator is coupled to the base of Q3 via diode D2.When the fuse is intact the base of Q3 will be pulled to a positive voltage by the resistor R5. The transistor will be ON and the LED D3 remains glowing. When the fuse of blown off, the base of Q3 will no longer be pulled to positive voltage and now the only biasing available at the base of Q3 will be the output from the astable multivibrator. Now the transistor Q3 will start switching in the frequency of astable multivibrator and the LED will blink in accordance.
Notes.
The circuit can be assembled on a Vero board.
This fuse circuit can be incorporated with any circuit that operates from 12V DC.
The type no of the transistors are not very significant and almost any NPN transistors will do the job.
The fuse F1 can be a metal wire fuse with your required rating.

Read more: http://www.circuitstoday.com/fuse-with-status-indicator#ixzz1PX8A1BQj

Remote control tester

Remote control tester
 
This is a simple remote controller tester circuit  based on infrared sensor IC TSOP 1738. When the IR waves fall on the sensor it output changes to low state.This makes the transistor Q1 ON and LED will blink according to the code contained in the signal.So for press of each button the LED blinks in different ways.This is a good indication of the working of remote.The diode D1drops 0.7 V to give the IC ~ 5V supply from the available 6V .R2 is a current limiting resistance.
Notes .
Use a 6V battery to power up the circuit.
This circuit can be used to test remotes operating in the 38Khz carrier frequency.Almost all remotes fall into this category so no problem.
We have more Remote Cir

Read more: http://www.circuitstoday.com/remote-controll-tester-circuit#ixzz1PSIbjaqW

Brightness controller for low power lamps

Brightness controller for low power lamps

  
The circuit given here can be used to control the brightness of low power incandescent lamps. The circuit is based on IC NE555 which is wired as an astable multivibrator with variable duty cycle. The output of IC is connected to the base of transistor Q1.The Q1 drives the lamp. The duty cycle of the multivibrator can be varied by varying the POT R4.As a result, the brightness of the lamp varies according to the position of the POT R4.The same circuit can be also used for speed control of small DC motors.
Notes.
The lamp L1 can be a 6V / 200 mA lamp.
The switch S1 can be SPST ON/OFF switch.
The IC1 must be mounted on a holder.
The circuit can be wired on a good quality PCB or common board.

Read more: http://www.circuitstoday.com/brightness-controller-for-low-power-lamps#ixzz1PSGZtjfu
Free counters!