Unity Gain Follower by IC LM741

Unity Gain Follower by IC LM741

This is the Voltage Follower used to transfer or copy a voltage from a first circuit (Vin) to a second circuit (V out),with gain rate is equal to 1 only, that is AV = Vout/Vin = 1 ; Vout = Vin.
The input has high impedance, and the output is low impedance.

It prevents the first circuit from loading of the second circuit, the output current don’t lower.
红包扫雷苹果下载地址 We used the op-amp IC LM741 for this operation that is easily and low cost.

Unity Gain Follower by IC LM741
红包扫雷苹果下载地址 This be Unity Gain Follower by IC LM741 circuit, Use for fine impedance tall from go to low. Be compared as the bumper of electronics circuit well. By this easy last circuit extend a contract that go out to pin 2 be making expansion ratio equals to one. make Vout = Vin

Transistor intercom circuit.


红包扫雷苹果下载地址here is a simple but effective intercom circuit that is based fully on transistors.the circuit is based on a three stage rc coupled amplifier. when the pushbutton s2 is pressed, the amplifier circuit wired around t1 & t2 becomes an astable multivibrator and starts producing the ringing signals. these ringing signals will be amplified by the transistor t3 to drive the speaker. when the push button s2 is released the circuit will behave as an ordinary amplifier and you can talk to the other side through it.

to construct a two way intercom, make two identical copies of the circuit given below and connect it according to the given connection diagram. the stand by current consumption of this circuit is around 20ma.


Circuit diagram with Parts list.

Transistor intercom circuitjpg


Connection diagram.

Transistor intercom connection jpg



  • Assemble the circuit on a good quality PCB.
  • Use 9V PP3 battery for powering the circuit.
  • The Mic M1 can be condenser micro phone.
  • Use push to ON type push button switch for S2.
  • Use a slide switch for switch S1.S1 can be used to power the circuit.


Telephone off-hook indicator


T红包扫雷苹果下载地址he circuit depicted here can be used as an indicator when the telephone receiver is off-hook. The circuit can be in corporated with old telephones that does not have such an indicator.

the circuit uses a complementary darling to pair using q1 (2n3904)and q2 (2n3906) to sense whether the receiver is off hook and glows a led to show the condition.

Circuit diagram with Parts list.

Telephone in use indicator circuitJPG


  • The LED must glow when the circuit is not connected to the telephone line as well as when the telephone is off-hook.
  • If the LED does not go OFF when the receiver is restored on hook change the value of R2 so that about 3.5 V comes across it.
  • The circuit can be powered from a 3V battery.

Simple Lamp Dimmer/ Fan Regulator

A Lamp Dimmer/Fan Regulator Circuit

We have modified this circuit: – Take a look

Description .

This is the circuit diagram of the simplest lamp dimmer or fan regulator.The circuit is based on the principle of power control using a Triac.The circuit works by varying the firing angle of the Triac . Resistors R1 ,R2 and capacitor C2 are associated with this. The firing angle can be varied by varying the value of any of these components. Here R1 is selected as the variable element . By varying the value of R1 the firing angle of Triac changes (in simple words, how much time should Triac conduct) changes. This directly varies the load power, since load is driven by Triac. The firing pulses are given to the gate of Triac T1 using Diac D1.


assemble the circuit on a good quality pcb or common board.the load whether lamp ,fan or any thing ,should be less than 200 watts. to connect higher loads replace the triac bt 136 with a higher watt capacity triac . all parts of the circuit are active with potential shock hazard.so be careful.

I advice to test the circuit with a low voltage supply (say 12V or 24V AC) and a small load (a same volt bulb) ,before connecting the circuit to mains.

Parts List

r1 1o k 1 watt resistor

红包扫雷苹果下载地址r2 1o0 k potentiometer (variable resistance)

c1 0.1 uf (500v or above ) polyester capacitor

红包扫雷苹果下载地址t1 bt 136 triac

d1 db2 diac

Fan Regulator Circuit Diagram

Lamp dimmer and fan regulator

BT 136Triac Necessary Data.

BT136 specification

红包扫雷苹果下载地址bt 136 specifications

Plant moisture level monitor


here is a simple circuit that will give a visual indication when the soil water level inside your flower pot goes low below a certain limit.

the u1c and associated components are wired as an oscillator producing a 2khz square wave. this square wave is given to one gate input of u1d via a variable potential divider former by r1 and r2.when the resistance across the probes a and b are low that is when soil moisture level is high, the c2 will divert the square wave to ground. the output of u1d will be high. the u1 a inverts this high state to low and so the ic u1b is blocked from producing oscillations. the led will remain off. when there is no moisture across the probes, the c2 cannot bypass the 2khz signal to the ground and it appears at the gate input of u1d.the output of u1d goes low, and it is inverted to high by u1a.the oscillator wired around u1b is activated and it starts oscillating. these oscillations are amplified by q1 to drive the led and led starts pulsating as an indication of low moisture. since square wave is used there wonã¢â€â™t be any oxidation on the probes. the resistor r7 limits the current through led and ensures a longer battery life.

Circuit diagram with Parts list.

Plant watering monitor circuit


  • Power the circuit from a 3V battery.
  • Two metal wires 10 cm long and 5cm apart driven into the soil will do the job for probes.
  • The probes are to be connected at the terminals A and B shown in circuit.
  • Capacitors C1 and C2 must be polyester type.
  • The IC U1 is a quad two input Schmitt NAND IC 4093.
  • The sensitivity can be adjusted by varying the preset R2.
  • Mount the IC on a holder.

Mosquito repeller power saver


红包扫雷苹果下载地址almost all liquidator type mosquito repellers are rated 5watts. it is a pretty energy consuming game when these repellers are operated through out the night. even though these liquidators are switched on and off in discrete intervals there will be no considerable loss in the effectiveness, and more over there will be a great saving of energy. then why can’t we do that and that’s why i designed this circuit.

the circuit is nothing but an astable multivibrator designed of ic ne 555 (ic1) operates in a frequency determined by the values of r1 and c2. when the power is switched on the out put of the ic goes high. this makes q1 to conducts and the relay connects the mains supply to the repeller plugged in the socket shown. after the set time the output of the ic goes low and now the repeller is removed from mains by the relay. this cycle repeats and the repellent will be switched on and off in frequent intervals, saving a lot of power. diodes d2, d3 forms a half wave rectifier with c1 as the filter, supplies the circuit with power.

Circuit diagram with Power supply.

Mosquito Repeller Power Saver Circuit

mosquito repeller power saver circuit


  • Assemble the circuit on a good quality common board or PCB.
  • The intervals of ON and OFF can be adjusted by varying Preset R1.
  • Some parts of the circuit are live with potential shock hazard.Be careful.

Mobile incoming call indicator


红包扫雷苹果下载地址this circuit can be used to escape from the nuisance of mobile phone rings when you are at home. this circuit will give a visual indication if placed near a mobile phone even if the ringer is deactivated.

when a call is coming to the mobile phone, the transmitter inside it becomes activated. the frequency of the transmitter is around 900mhz.the coil l1 picks up these oscillations by induction and feds it to the base of q1. this makes the transistor q1 activated.since the collector of q1 is connected to the pin 2 of ic1 (ne555) , the ic1 is triggered to make the led connected at its output pin (pin 3) to blink. the blinking of the led is the indication of incoming call.

Circuit diagram with Parts list.

Mobile incoming call indicator circuitJPG


  • The coil L1 can be made by making 150 turns of 36 SWG enameled copper wire on a 5mm dia plastic former.Or you can purchase a 10 uH coil from shop if available.
  • The circuit can be powered from a 6V battery.
  • Assemble the circuit on a good quality PCB.
  • C1 & C3 are to be polyester capacitors.
  • The electrolytic capacitor C2 must be rated 10V.

Simple Water Level Indicator Diagram

Water Level Indicator


This is the circuit diagram of a simple corrosion free water level indicator红包扫雷苹果下载地址 for home and industries. In fact the the level of any conductive non corrosive liquids can be measured using this circuit. The circuit is based on 5 transistor switches. Each transistor is switched on to drive the corresponding LED , when its base is supplied with current through the water through the electrode probes.

One electrode probe is (F) with 6V AC is placed at the bottom of tank. Next probes are placed step by step above the bottom probe. When water is rising the base of each transistor gets electrical connection to 6V AC through water and the corresponding probe. Which in turn makes the transistors conduct to glow LED and indicate the level of water. The ends of probes are connected to corresponding points in the circuit as shown in circuit diagram.Insulated Aluminum wires with end insulation removed will do for the probe. Arrange the probes in order on a PVC pipe according to the depth and immerse it in the tank.AC voltage is use to prevent electrolysis at the probes. So this setup will last really long. I guarantee at least a 2 years of maintenance free operation. That’s what I got and is still going.


红包扫雷苹果下载地址t1 – t5 bc 548 or 2n2222 transistors

红包扫雷苹果下载地址r1-r5 2.2k 1/4 w resistors

r6-r10 22k 1/4 w resistors

d1 – d5 led’s ( color your choice)


U红包扫雷苹果下载地址se a transformer with 6V 500 mA output for power supply. Do not use a rectifier! we need pure AC. Use good quality insulated Aluminum wire for probes. If Aluminum wires are not available try Steel or Tin.Copper is the worst. Try the circuit first on a bread board and if not working properly, make adjustments with the resistance values. This is often needed because conductivity of water changes slightly from place to place. The type number of the transistors used here are not critical and any small signal NPN transistor will do the job. Few other suitable type numbers are BC546, BC107, PN2222, BC337, BF494, ZTX300, BEL187 etc. The circuit can be enclosed in a plastic box with holes for revealing the LEDs .

Water Level Indicator Circuit Diagram and Sensor Arrangement.


Simple water level indicator

红包扫雷苹果下载地址water level indicator


If you need a fully automatic water level controller circuit then try this circuit  . The circuit is fully based primarily on transistors. The sensing section is somewhat similar to this circuit but there is additional circuitry for switching the pump ON when the water level falls below a set level and the pump will be switched OFF when the tank is full. Few transistors , one 555IC and an electromagnetic relay is used for realizing the control section. The circuit is very simple cost effective , reliable and many guys have successfully assembled it.I am also working on a float type water level indicator/controller using the float type fuel gauge mechanism used in motor cycles.The level sensor section is  finished and now I am working on the control circuitry. I will add the circuit here as soon as it is finished

Note:- We have recently developed a much better and fully functional 红包扫雷苹果下载地址. This water level controller monitors the level of the over head tank  and automatically switches on the water pump when ever the level goes below a preset limit. You may see the circuit and try it.

Simple Relay Circuit

the following schematic illustrates the simple relay circuit diagram.

Simple Relay Circuit

红包扫雷苹果下载地址when the switch s is closed in a relay circuit, current flows in the coil, causing a strong magnetic field around the coil. the soft iron bar in the lamp circuit is attracted toward the right end of the electromagnet and makes contact with the conductor at a. a path is thus completed for current in the lamp circuit. when the switch is opened, the current flow through the electromagnet ceases and the magnetic field collapses and disappears. since the attraction for the soft iron bar by the electromagnet no longer exists, the iron bar is pulled away from the contact by the piece of spring steel to which it is attached. this opens the contacts at a and breaks the circuit for the lamp.

Touch Switch Circuit

Touch Switch Circuit using NE 555


This is the circuit diagram of a small touch plate controller using IC .This circuit is ideally useful for making touch operated , 红包扫雷苹果下载地址,toys etc which when touched on the touch plate operates the for a preset time and the turns off automatically.

红包扫雷苹果下载地址this circuit is realized by utilizing the high input impedance of trigger pin of the 555 ic.when the ic is triggered by the induced voltage of human body the output goes high for a time determined by r1 and c1.the transistor is used to drive the relay.the relay contacts can be used to drive the load like bell, motor , lights etc.


红包扫雷苹果下载地址to make the touch plate cut a 1 square cm thin metal sheet.

to setup the circuit connect to and adjust r1 while keeping touching on the touch plate.stop at the point where relay activates.if relay is in the activated state initially then do the same until the relay is deactivated.

Touch Switch Circuit Diagram

Touch switch circuit