Cascaded Timer using 4528 IC

This is a simple design circuit that uses a CMOS dual re-trigger mono stable IC 4528 in a cascade timer circuit. The CMOS timer can be easily cascaded with other similar 4528 circuits to lengthen the timing needed. This is the figure of the circuit.


The timing of the project is determine by VR3 and C1 for the first stage and VR4 and C2 for the second stage. Once button S1 is pressed, the 1st stage output pin 6 logic level will go high and output pin 7 will go low for the preset time which is determined by VR3 and C1. When the time is up, the output pin 6 will go low and pin 7 high. At this moment of time, pin 7 will positive trigger the 2nd stage of the timer at pin 12. Output pin 10 will go high and pin 9 will go low for a time determine by VR4 and C2 before the cycle end with pin 10 back to low and pin 9 to high.

Universal Power Supply Circuit

This is a design circuit for a power supply, but this design is universal power supply. This circuit is using LM371 for control operation. This is the figure of the circuit.


The Universal Power Supply output voltage can be set to anywhere in the range 1.5V to 30V by selecting two resistances. By using a potentiometer, R2, as one of the resistors you can dial up the output voltage wanted. Either AC or DC input can be supplied to the PCB via a socket or terminal block. Connection can be either way around. This is because we have provided a bridge rectifier on board. The input DC voltage to the regulator must be at least 2.5V above the required output voltage. An off/on switch is provided. The LM317 will provide slightly higher output voltages than 30 volts. To be safe for continuous operation the maximal input DC voltage to the regulator should not be over 33V. With a 2.5V to 3.0V drop across the regulator this will give a regulated output of 30V. You can draw up to 1.5A from the LM317.

When external capacitors are used with any IC regulator it is good practice to add protection diodes to prevent the capacitors discharging back into the regulator in the event of abnormal operating conditions, like a sudden short circuit on the input or the output, or a back emf from an inductive load. That is the function of D1 and D2.

Light Sensor Circuit Using Op Amp 741

This is a one of the light sensor. This circuit is a dark sensor that is based on op – amp 741 IC as main control. This circuit is a simple design for sensor the light at the night. This is the figure of the circuit.


For sensor the light is using LDR. Operation of the circuit is under normal conditions the resistance of the LDR is high, keeping pin 2 low. When light falls onto the LDR the resistance drops to a couple hundred ohms and triggers pin 2 high which biases the base of Q1 via pin 6 and R4 and in turn activates the relay. Trimmer pot P1 and the two 470 ohm resistors, R2 and R3, are a voltage divider to adjust for sensitivity.

If you want the action reversed (make it a dark sensor), change the positions of the LDR and R1. If the relay 'chatters', add a bit of hysteresis by adding a 100K to 1Meg-ohm resistor (R6) over pins 6 and 2 of the 741 op-amp, but in most cases 100K to 330K will do the job. The LDR is a regular, general purpose type. D1 serves as a spark-arrestor when the relay contacts open. This circuit power supply is using 12 V DC.

Door Knock Alarm Circuit

In the some building is need to using good security. For some example is using this design circuit. The door knock alarm is a simple design for the simple security for the house. This circuit is based by sensor piezoelectric wafer for detected the alarm. This is the figure of the circuit.


Operation of the circuit is the resistor R5 determines the knock sound sensitivity. The value shown should work in most cases. The box could be hard mounted to the door or suspended at about the middle of the door, by a string from the top of the door in such a way that the box rests against the door. It is suggested that the circuit be housed in a plastic box with a 9v battery holder.

DC to AC Inverter Using 555 IC

This is a design for AC inverter circuit. This circuit is produces an AC output at line frequency and voltage. The circuit is using 555 IC as main control. This IC is configured a low frequency oscillator, tunable over the frequency range of 50 – 60 Hz by potentiometer R4. This is the figure of the circuit.


The principle work of the circuit is the IC feeds its output that amplified by Q1 and Q2 to input of the transformer T1. A reverse is connected filament transformer with necessary step-up turns ratio. A capacitor C4 and coil L1 filter the input to T1, assuring that it is effectively a sine wave. Adjust the value of T1 to your voltage. Replacement types for Q1 are: TIP41B, TIP41C, NTE196, ECG196, etc. Replacement types for Q2 are: TIP42B, TIP42C, NTE197, ECG197, etc. The input voltage of the circuit is anywhere from +5V to +15Volt DC.

Birdie Doorbell Circuit

This is a design circuit for a doorbell. This circuit can produces a sound like bird sound. This circuit controlled by transistor NPN. This is the figure of the circuit.


The operation of the circuit is beginning when P1 is of experimental value. Start with 220 Ohms or so and modify to suit your needs. The transistor is a general purpose kind and is not critical, almost any PNP type will work. L1 is a bell-transformer which is usually already present in the house. If you wish, you could use a battery instead of the bell transformer. Just hookup a 9-volt battery (or wall adapter)to points 'A' and 'B' (A=+) the diode (D1) is to protect the circuit from accidental polarity reversal and is optional, but required as a rectifier for use with the bell transformer. T1 is a General Purpose PNP transistor and probably anything will work. L2 comes out of an old am transistor radio. They look like miniature transformers and are usually colored red or green. You have to fiddle with different transformers as the sound can vary depending on the value. The loudspeaker is a 8 Ohm type and must be larger than 200milli-Watt. I used a 2Watt type, but anything over 0.2W will do.

Touch Switch Circuit Using 555 IC

This is a circuit for touch switch circuit. This circuit is almost same with touch door alarm. This circuit uses a 555 timer as the bases of the touch switch circuit. This is the figure of the circuit.


The operation of this circuit is begin, when the plate is touched the 555 timer is triggered and the output on pin 3 goes high turning on the LED and the buzzer for a certain period of time. The time that the LED and the buzzer is on is based on the values of the capacitor and resistor connected to pin 6 & 7. The 10 M resistor is on pin 2 causes the circuit to be very sensitive to the touch.

Touch Door Alarm Circuit Using 555 Timer IC

This is a design simple alarm that can be used to provide a audible alarm when someone touches the door knob or handle of your room. The door knob or handle must be made of metal for the circuit to work. The main chip in the circuit is a 555 timer which will be triggered if a hand comes close to or touches the door knob.


The circuit attaches to the door knob at the end of the 1 Mega ohm resistor. This is operation of the circuit. Once the timer is triggered the LED will light and the UJT will output a tone to the speaker. The timers will time out in 5 seconds. The sensitivity of the trigger can be changed by changing the 1 Mega ohm resistor to another value. The 5 second time out can be adjusted by changing the value of the resistor connected between pin 8 and pin 7. The output tone can be changed by changing the RC values on the base of the UJT.

Positive to Negative Converter Using Direct Feedback

This is a design circuit for positive to negative converter. The negative feedback (NFB) pin, enables negative output regulators to be designed using direct feedback. In the circuit shown in Figure 3, a 2.7 V to 13 V input, –5 V output converter, the output is monitored by the NFB pin and a simple divider network. No complex level shifting or unusual grounding techniques are required. The S/S pin is used to synchronize the switching frequency to a 600 KHz external clock signal. This is the figure of the circuit.


The switch clamp diodes, D2 and D3, prevent the leakage spike from the transformer, T1, from exceeding the switch’s absolute maximum voltage rating. The Zener voltage of D2 must be higher than the output voltage, but low enough that the sum of input voltage and clamp voltage does not exceed the switch-voltage rating.

DC to DC Converter Circuit

This is a design for DC to DC converter module. The module is a device that accepts a DC input voltage and produces a DC output voltage. Normally the output voltage produced is at a different voltage level than the input. DC to DC converters are used to provide noise isolation as well as power bus regulation. In this circuit, converter is using LTM4600. Look to the figure of the circuit.


The 10A High efficiency DC/DC converter module LTM4600 is a complete 10A, DC/DC step down power supply. Included in the package are the switching controller, power FETs, inductor, and all support components. Operating over an input voltage range of 4.5V to 20V, the LTM4600 supports an output voltage range of 0.6V to 5V, set by a single resistor. This high efficiency design delivers 10A continuous current, needing no heat sinks or air flow to meet power specification. Only bulk input and output capacitors are needed to finish the design.

Counter Down Timer Circuit

This circuit is design of the counter timer that using countdown calculation. This circuit is using 555 IC as main control. 555 IC is a counter IC and a transistor switch to activate a relay either ON/OFF (mode selected by a jumper) as soon as the counting period is over. The circuit consists of an oscillator, a ripple counter and two switching transistors. This is the figure of the project circuit.


The 555 is configured in the standard astable oscillator circuit designed to give a square wave cycle at a period of around 1 cycle/sec. The output pulse from pin 3 of the 555 is fed to the clock input pin 10 of the 14-stage binary ripple counter, the 4020 (or 14020.) Operation of the circuit is explained in next. In this circuit C3, R4 and D1 are arranged as a power-on reset. When power is applied to the circuit C3 is in a discharged state so pin 11 will be pulled high. C3 will quickly charge via R4 and the level at pin 11 falls thus enabling the counter. The 14020 then counts clock pulses until the selected counter output goes high. D1 provides a discharge path for C3 when the power is disconnected. You can change the components values of R1 and C1 to set the 555 count frequency to more than 1.0 Hz. If you change the count to 10 seconds then a maximum timer delay of 81920 seconds, or 22.7 hours, can be obtained.

The output from the 4020 goes to a transistor switch arrangement. Two BC547 are connected so that either switching option for the relay is available. A jumper sets the option. The relay can turn ON when power and counting start then turn OFF after the count period, or it can do the opposite. The relay will turn ON after the end of the count period and stay on so long as power is supplied to the circuit. Note that the reset pin of the 555 is connected to the collector of Q1. This enables the 555 during the counting as the collector of Q1 is pulled low.

An Adjustable Power Supply Using Two Amp

This is a circuit for power supply that has an output of 0v to 12v at 700mA with a transformer that is rated at 1-amp (such as M-2155) or 1.4amp for a transformer that is rated at 2-amp (such as M-2156). This is a simple design for power supply. This power supply can adjusted. This is the figure of the circuit.


Operation of the circuit is begin, first the mains voltage is reduced to a usable level by the transformer. Two different low-cost transformers can be used. The M2155 is a 1 amp type and M2156 is a 2 amp type. This is the AC rating and when you connect any transformer to a DC power supply circuit you must de-rate the current rating by 30% to give the maximum DC current that can be delivered by the power supply. The BD 679 regulator transistor must be heat sink if any more than 100-200mA is required and will certainly need a large heat sink when the full rated current flows. The heat generated in the transistor is due to two factors. One is the current flow. Obviously, as more current flows, the transistor will get hotter. But the other factor is the voltage across the transistor. If you are drawing 100mA at 12v, the transistor will rise to a certain temperature. If you reduce the output to say 6v, while still drawing 100mA, the transistor will get hotter because the voltage across it will be greater. In the first case the voltage across the transistor will be the voltage from the bridge rectifier minus the output voltage. Our figures were 22v - 12v = 10v across the transistor.

5V to 12V Boost Converter Using LT1370

This is a design for booster converter. This booster can convert the voltage from 5 V to 12 V. This circuit is using LT1370 IC as main control. The high 6A switch rating permits the circuit to deliver up to 24W. This is the figure of the circuit.


The inductor needs to be chosen carefully to meet peak current values. The output capacitor can see high ripple currents often, as in this application, higher than the ripple rating of a single capacitor. This requires the use of two surfaces mount tantalums in parallel; both capacitors should be of the same value and manufacturer. The input capacitor does not have to endure such high ripple currents and a single capacitor will normally suffice. The catch diode, D1, must be rated for the output voltage and average output current. The compensation capacitor, C2, normally forms a pole in the 2Hz to 20Hz range, with a series resistor, R3, to add a zero at 1kHz to 5kHz. The S/S pin in this example is driven by a logical on/off signal, a low input forcing the LT1370 into its 12mA shutdown mode.

Phone Recorder Circuit

This is a schematic for recording the conversation in telephone. One constructed, this switch will allows you to automatically turn on your tape recorder when you pick up the handset of your telephone. This circuit is designed to work for the newer 1.5V and 3V tape recorders as well as the usual 6V or 12V ones. This circuit is control based on transistor and FET’s. Looking in the figure of schematic.


The circuit is fall into two part and these can be easily seen in the schematic. On the left are the connections to each telephone line and to the MIC socket of the tape recorder. The diode and capacitors ensure that no DC voltages pass through to the input of the MIC while the RC network clips large transients. On the right is the circuit which detects when the handset has been lifted and which then turns on the FET. The trim pot adjusts the voltage level of this circuit. The voltage of the normal telephone line is between 40 to 60 volts (depending on country and telephone system.) When you pick up the handset of the telephone the voltage falls to between 6 and 12 volts. It is this drop in voltage which is used to control the tape recorder through the REMOTE connector. When the line voltage is high the base of the BC548 is pulled high so the transistor is turned on. This pulls the gate of the FET down to less than 1 volt. This shuts off the FET.

When the line voltage falls (that is, the handset is picked up) the BC548 will turn off, adjust the variable resistor if it does not. So the FET gate potential rises to the 10 volts set by the zener diode. This turns the FET on to high efficiency conduction mode. Different recorders may have different polarities in their REMOTE sockets. To allow for this a PCB mounted switch has to be added to the board which will reverse the polarity of the REMOTE switch just by switching it.

A Dice Circuit Using LED

This is a design circuit for a game a dice. This circuit uses 7 LED to simulate the rolling of a dice after the Roll button is pushed. It has a slowdown feature so that you can see the 'rolling' of the dice slowing down and then stop. This is more satisfying than the usual LED dice circuit which just stops after the button is released. This circuit is work with based on 555 IC and 14017. IC 14017 is decade counter. This is the circuit figure.


The principle work of the circuit is when the switch is turned on Q4 is turned off (its base is pulled high by the 3.3M ohm resistor) and the 555 oscillator is not oscillating. Pressing the ROLL switch immediately charges the 470nF capacitor, Q4 is turned ON and the 555 starts to oscillate. The 470nF gradually discharges via the 10M ohm and 3.3M ohm resistors and turns Q4 off. The 555 is connected as an oscillator. The frequency of oscillation is generally independent of the potential difference across the pins. However, as Q4 turns off the frequency becomes dependent on the voltage. The counter CP0 is advanced by a LOW to HIGH transition from pin 3 of the 555 to pin 14. The first six outputs from the 14017 labeled are labeled by O0 to O5. The next output O6 from pin 5 is connected to the Reset pin 15.

Dazzling Intensity Circuit in Light a White LED

This is a circuit that is used as indicators or to provide illumination, LEDs are hard to beat in efficiency, reliability, and cost. White LEDs are rapidly gaining popularity as sources of illumination, as in LCD backlights, but with forward voltages typically ranging from 3 to 5V, operating them from a single cell presents obvious difficulties. This circuit is based on SN74AUC1G14 IC’s. This is the figure of the circuit.


The operation of the circuit begin, when you first apply battery power, Schottky diode D1 conducts, and the familiar Schmitt-trigger astable multi vibrator starts to oscillate at a frequency determined by timing components C2 and R1. When IC1’s output goes high, transistor Q1 turns on, and current begins to ramp up in inductor L1. At the end of tON, when the inverter output goes low, Q1 turns off, and the voltage across L1 reverses polarity. The resulting “flyback” voltage immediately raises Q1’s collector voltage above VBATT and forward-biases the LED and D2, which appear in series.

LED Driver Circuit Delivers Constant Luminosity

This is a design of LED driver circuit. This circuit is work with based on 2two transistor. This is the figure of the design circuit.


The operation of the circuit is begin from the output current is almost constant over an input-voltage range of 1.2 to 1.5V and is insensitive to variations of transistor gain. Transistors Q1 and Q2 form an astable flip-flop.R1 and C define the on-time of Q2. During that time, Q1 is off, and the voltage at the base of Q1 and the current in inductor L ramp up. When the voltage at the base of Q1 reaches approximately 0.6V, Q1 turns on, and Q2 turns off. This switching causes “fly back” action in inductor L. The voltage across the inductor reverses, and the energy stored in the inductor transfers to the LED in the form of a down-ramping pulse of current. During fly back time, voltage across the LED is approximately constant. The voltage for yellow and white LEDs is approximately 1.9 and 3.5V, respectively. When the current through the LED falls to zero, the voltage at the collector of Q2 falls sharply, and this circuit condition triggers the next cycle

Thermostat Circuit Using LM358

Thermostat is one of the common device used to control the temperature of a space be it a warehouse, a room, a hall or an office. This thermostat circuit will focus on the heating control of a space that uses electric heater as its source of heating. It basically consists of a comparator that controls the ON and OFF of the electric heater based on the sensor temperature. This thermostat is based on op-amp LM358 to control the operation this circuit. Look this figure of circuit.


The LM358 op amp is used as a comparator to sense the inputs of the reference voltage (PIN 3) and room temperature (PIN 2). The thermistor used is a NTC (negative temperature coefficient) type where its resistance will drop when the temperature increases and vice versa. It has a resistance of 20K ohm at 25 degree Celsius. When the room temperature drops, the thermistor resistance will go up and hence the output of the operational amplifier will be low. This cause the relay to turn OFF and the heater will conduct until the temperature of the room rises again. To calibrate this circuit, we using variable resistor VR1. Set the lever of the slide potentiometer or rotary potentiometer VR2 to 25 Celsius location. Place the thermistor at a space where the temperature is at 25 Celsius. By varying VR1, set the resistance at the position between the ON and OFF of the relay. Use a suitable contact relay rating according to the load of the heater.

Shut Off Tone Generator Circuit

This is a circuit for tone generator. This circuit is once the switch to the 9V power supply is connected, the alarm will trigger at a frequency of approximately 1.27 kHz. It will remain ON for duration of approximately 170 seconds or 2.8 minutes before it stopped. This circuit is work with based on 555 IC. This is the figure of the circuit.


In this circuit, we used two 555 timers. U2 is configured as a timer in astable mode. Once triggered, it will emit a frequency from its output at pin 3 that will drive a Q1 transistor. Q1 transistor will turn ON and OFF according to the frequency of the circuit. It will in turn used to drive a 8 ohm loud speaker to emit a loud audible sound. The frequency of the sound can be adjusted by changing the values of R3= 47K, R4= 33K and capacitor C1=10nF. Change the values of these components and by using the formula for astable mode, the frequency of the sound can be obtained.

U1 circuit is used as a delay circuit which is configured as a mono stable mode. It is a one shot multivibrator that will generate a pulse at its output at pin 3 which will disable the astable circuit U1. In this circuit, pin 2 of U1 will go to logic 0 when the power supply is connected via the capacitor E1 and hence circuit U2 is immediately triggered.

Digital Distance Counter Measurement

When we take a journey, we must to attention the distance that missing. We need a measurement to measure the distance. In the bicycle, we know that the instrument to measure the distance is make by analog measurement. The design circuit is used to measurement distance with digital measurement. The hardware is located in a small box slipped in pants' pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km and its dot is always on to separate Km from hm. This is the figure of the circuit.


The rightmost display D1 (the least significant digit) shows hundreds meters and its dot illuminates after every 50 meters of walking. A beeper (excludable), signals each count unit, occurring every two steps. A normal step was calculated to span around 78 centimeters, thus the LED signaling 50 meters illuminates after 64 steps (or 32 operations of the mercury switch), the display indicates 100 meters after 128 steps and so on. For low battery consumption the display illuminates only on request, pushing on P2. In any case, the most critical thing to do is the correct placement of the mercury switch inside of the box and the setting of its sloping degree.

Operation of the circuit is begin from IC1A & IC1B form a mono stable multi vibrator providing some degree of freedom from excessive bouncing of the mercury switch. Therefore a clean square pulse enters IC2 that divides by 64. Q2 drives the LED dot-segment of D1 every 32 pulses counted by IC2. Either IC3 & IC4 divide by 10 and drive the displays. P1 resets the counters and P2 enables the displays. IC1C generates an audio frequency square wave that is enabled for a short time at each mono stable count. Q1 drives the piezo sounder and SW2 allows to disable the beep.