Simple Sound Processor

Simple Sound Processor presented here is an ultra-simple circuit module suitable for almost all basic electronics and microcontroller projects. For example, this module can be used as a front-end in an electronics project to detect and process ambient sound in an efficient manner. Even less-experienced hobbyists will find the construction of the circuit on a general purpose printed circuit board a fairly easy affair, since there is no perplexed wiring and all components are housed on the board. As the circuit has no critical adjustment points it is immediately ready for real-world applications.

The acoustic sensor in the circuit is a standard omni-directional foil electret microphone (MIC). Sound signals picked up by this microphone is processed by two BC547B transistors (T1 and T2). Pre-processed signals from this section is linked to the monoshot brick realized using the popular NE555N chip (IC1). The whole module can be powered from any standard 5 volt dc supply. Pins 1 and 2 of the 3-pin JST connector (J1) denotes VCC (+5V) and GND (0V) connections respectively, while the final 3rd pin works as the digital signal output (DO) pin.

Simple Sound Processor Circuit Diagram:

Final component in the circuit – IC2 – is a single chip encapsulated in an SSOP5 package BU4S584G2 which is a single Schmitt trigger inverter, added here to ensure high degree of noise tolerance. However, this is not a critical component, so you can replace it with direct equivalents, if available. Pin description and input/ouput table of BU4S584G2 is shown below:

Working of the sound processor circuit is very simple and straight forward. The circuit captures incoming sound signals through the microphone. When the circuit detects a sound activity it generates a digital/logic-level (active-low state) output for a pre- settled duration fixed by the 10K pot (P1). This output can be given to almost all micro controllers for further processing. Although this little circuit module is not intelligent to separate different sounds, it is very useful in making general/microcontroller/robotic projects integrated with sound activation features. As an example, consider the possibility of building a security camera system which takes pictures only when triggered by an audible acoustic wave frequency.

Lab Note:

If you are looking for some other simple solution, you can replace the microphone electronics with a single-transistor circuit as shown below:

Prototype tested with both front-end circuits, but a drop-off in sound detection sensitivity was noticed with the second option!

By: T.K. HAREENDRAN

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Door Opening Alarm with Sound Alert

The door opening alarm circuit or “Front Office Visitor Alert” is used for alerting you when a customer is at your office/shop. It will produce a beep sound when each new customer or visitor is entering, and will automatically switch OFF after few seconds.

In this circuit timer IC NE555 is used as monostable mode. Initially when the door is closed; reed switch (normally open type) near the magnet is closed. When the door is opened by someone, the reed switch near the magnet is open and the base of Transistor Q1 goes low through the 10k Resistor R2, and so Transistor Q1 is ON. At this time trigger pin 2 of the IC1 go low, it triggers the monostable built around IC NE555. Once triggered, output pin 3 of IC1 goes high, and both Buzzer and LED are turned on.

At this time the Capacitor C1 starts charging through the Transistor Q1. After few seconds the Buzzer and LED will automatically switched OFF. When the door is closed the T ransistor base become high, Transistor Q1 goes OFF and the Capacitor C1 starts discharging through the Resistor R4 is connected parallel with the capacitor C1. You can change the time period of IC1 by changing the values of resistor R5 and capacitor C2.

Assemble the circuit on a general-purpose PCB, enclose in a suitable cabinet and the magnet is fixed on the door frame and the reed switch is fixed on the door, near the magnet. The circuit can be powered from a 6V battery or from mains by using a 6V power adaptor.

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Layman’s RGB LED Module Project

Layman’s RGB LED module is an ultra-simple project realized without any microcontrollers. An RGB LED can be driven with a cmos presettable up/down counter. This is accomplished by connecting the three source outputs (Q1 to Q3) from a CD4029 cmos chip and configuring the device as a presettable counter. The solution presented here is intended to drive red, green, and blue LEDs in a common anode configuration. Color pattern (and intensity balance) is then controlled with the help of an external clock signal generator circuitry.

The CD4029 IC

CD4029 IC consists of a four-stage binary or BCD-decade up/ down counter with provisions for lookahead carry in both counting modes. The inputs consist of a single CLOCK, CARRY-IN (CLOCK ENABLE), BINARY/DECADE, UP/DOWN, PRESET ENABLE, and four individual JAM signals. Q1, Q2, Q3, Q4 and a CARRY OUT signal are provided as outputs. Binary counting is accomplished when the BINARY/DECADE input is high; the counter counts in the decade mode when the BINARY/DECADE input is low. The counter counts up when the UP/DOWN input is high, and down when the UP/DOWN input is low.

The RGB LED

With an RGB (Red-Green-Blue) LED, literally you will be able to produce any color. At first glance, a 5mm RGB LED looks just like the regular 5mm LEDs, however, inside the standard package, there are actually three LEDs; one red, one green and yes, one blue. By controlling the brightness of each of the individual LEDs you can mix pretty much any color you want. A common anode RGB LED is the most popular type, and it is nothing more complicated than three one colour LEDs (one red, one green, and one blue) housed in a single package. However, rather than having 6 leads (cathode and anode for each LEDs) it has only 4 leads; one cathode for each colour (RGB), and the common anode (CA). Usually, the common anode of the LED package is the second pin from the flat side of the LED package. It is also the longest of the four leads. This lead will be treated as the “common” pin of the RGB LED.

The RGB LED Module

As said, the circuit is built around CD 4029 IC and a few other external components. The finished module can be powered from any “clean” 5-Volt dc supply source for driving the RGB LED connected at the output of the circuit. In addition, the module calls for a suitable clock pulse at its input which can be supplied from a suitable clock generator wired around discrete components, or from a microcontroller based circuitry. Needless to say, this inputted clock signal determines the color pattern and intensity balance of the RGB LED’s aesthetic visual output. Refer the following application circuit:

RGB LEDs have differing forward voltages (VF) for the red, green, and blue LEDs. When drived by a 20mA per LED current, the red LED element of the RGB LED used here has a forward voltage of about 2V. The green and blue LEDs have forward voltage levels of about 2.4V and 3.6V respectively. Note that the forward voltage drop for each LED within the RGB LED need to be well-equalized in order to match LED performance over the operating range. These ballast resistors are used in the prototype; RR = 150R , RG = 120R, RB = 68R.

The Clock (CLK) Signal

Since the CARRY-IN (CI/pin 5) and PRE-SET ENABLE (PE/pin1) inputs of IC1 (CD4029BE) are held at low level, the counter is advanced one count at the positive transition of clock signal fed through the clock input (CLK/pin 15). Advancement is inhibited when PRESET ENABLE input (pin1) is pulled to a high-level (here by Q4 output of IC1). Based on this, we can feed a suitable clock signal to the module (through J1) for driving the onboard RGB LED as per our requirement. For testing your finished circuit, just try out an external clock pulse generator centered around the single most useful integrated circuit in history, the 555 timer chip. Refer the following sample application circuit:

Here, when wipers of P1 and P2 are bolted at their mid-travel (ie. 5K value), output from NE555 is about 0.952 Hertz (frequency) @ 67 % (duty cycle). However, adding a 1N4148 diode between pins 7 and 6 of NE555 ( its anode to pin 7 & cathode to pin 6), this will changes to near 1.429 Hertz @ 50 %.

Hooked to CD4029?

Recently we published an “Improved Impulse detector” circuit based on the same chip CD4029. At that time CD4029 was wired as an upward counting decade counter. But now the same CD4029 works as a binary counter whose outputs continuously count in a binary progression between 1 to 7. These outputs drive the 2N3904 transistors (T1, T2 and T3) which, in turn, control each of the three colours of the RGB LED. Now it’s your turn; refer the CD4029 datasheet, and carefully walk through both circuits to find out the typical configuraton tricks used by us!

Author by: T.K. HAREENDRAN

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Dual Sensor 555 Timer Alarm

This electronic circuit project is a very simple alarm circuit that is based on the 555 timer integrated circuit. This alarm circuit can be used with many types of sensors like : light or temperature sensors. As you can see below some types of sensors that can be connected at this type of alarm circuit ( darkness , light , cold and heat sensor ).

Dual Sensor 555 Timer Alarm Circuit Diagram:
 

If the sensor detects that the temperature or light is outside of the desired range the alarm will be activated .By turning the  potentiometer from the base of Q1  you will modify the sensibility of the sensor . When the alarm is activated the Q2 transistor acts as an audio amplifier and speaker driver for the 16 ohms speaker .

This alarm circuit require a 12 volts DC power supply circuit:

 

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Police Lights associate crystal rectifier

This circuit uses a 555 timer that is setup to each runn in associate Astable operative mode. This generates a nonstop output via Pin three within the type of a sq. wave. once the timer's output changes to a high state this triggers the a cycle the 4017 4017 decade counter telling it to output consecutive sequent output high. The outputs of the 4017 ar connected to the LEDs turning them on and off.

Police Lights associate crystal rectifier Project:

 
Parts List:

1x - NE555 Bipolar Timer
1x - 4017 Decoded Decade
6x - 1N4148 Diode
1x - 1K Resistor (1/4W)
1x - 22K Resistor (1/4W)
2x - 4.7K Resistor (1/4W)
6x - 470 Resistor (1/4W)
1x - 2.2µF Electrolytic Capacitor (16V)
2x - BC547 NPN Transistor
2x - LED (Blue)
2x - LED (Red)
1x - 9V Voltage Battery

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IC 555 Design Note

The popular Timer IC 555 is extensively used in short duration timing applications. IC 555 is a highly stable integrated circuit functioning as an accurate time delay generator and free running multivibrator. But one of the serious problem in 555 timer design is the false triggering of the circuit at power on or when voltage changes. The article describes how IC555 is designed perfectly to avoid false triggering.

555 IC pin functions

• Pin1 Ground
• Pin2 Trigger
• Pin3 Output
• Pin 4 Reset
• Pin 5 Control voltage
• Pin 6 Threshold
• Pin 7 Discharge
• Pin 8 Vcc

Functional aspects of pins

Trigger Pin 2

Usually pin2 of the IC is held high by a pull up resistor connected to Vcc. When a negative going pulse is applied to pin 2, the potential at pin 2 falls below 1/3 Vcc and the flip-flop switches on. This starts the timing cycle using the resistor and capacitor connected to pins 6 and 7.

Reset pin 4
Reset pin 4 can be controlled to reset the timing cycle. If pin 4 is grounded, IC will not be triggered. When pin4 becomes positive, IC becomes ready to start the timing cycle. Reset voltage is typically 0.7 volts and reset current 0.1 mA. In timer applications, reset pin should be connected to Vcc to get more than 0.7 volts.

Control Voltage pin 5

Pin5 can be used to control the working of IC by providing a DC voltage at pin5. This permits the control of the timing cycle manually or electronically. In monostable operation, the control pin5 is connected to ground through a 0.01 uF capacitor. This prevents the timing interval from being affected by AC or RF interference. In the Astable mode, by applying a variable DC voltage at pin 5 can change the output pulses to FM or PWM.

Threshold pin 6 and Discharge pin 7

These two inputs are used to connect the timing components- Resistor and Capacitor. The threshold comparator inside the IC is referenced at 2/3 Vcc and the trigger comparator is referenced at 1/3 Vcc. These two comparators control the internal Flip-Flop of the circuit to give High or Low output at pin 3.When a negative going pulse is applied to pin 2, the potential at pin2 drops below 1/3 Vcc and the trigger comparator switches on the Flip-Flop. This turns the output high. The timing comparator then charges through the timing resistor and the voltage in the timing capacitor increases to 2/3 Vcc.( The time delay depends on the value of the resistor and capacitor.

That is, higher values, higher time).When the voltage level in the capacitor increases above 2/3 Vcc, the threshold comparator resets the Flip-Flop and the output turns low. Capacitor then discharges through pin 7.Once triggered, the IC will not responds to further triggering until the timing cycle is completed. The time delay period is calculated using the formula T= 1.1 Ct Rt. Where Ct is the value of Capacitor in PF and Rt is the value of Resistor in Ohms. Time is in Seconds.

How to eliminate false triggering?

The circuit diagram shown below is the simple monostable using IC 555. To eliminate the false triggering resistor R1 and Capacitor C1 are connected to the reset pin 4 of the IC. So the reset pin is always high even if the supply voltage changes. Moreover capacitor C3 connected close to the Vcc pin 8 acts as a buffer to maintain stable supply voltage to pin 8. Using this design, it is easy to avoid false triggering to a certain extent.

555 Monostable circuit 

 
A ready recknor to select timing resistor and capacitor

 

Theoretically long interval is possible with IC 555,but in practical conditions, it is difficult to get more than 3 minutes. If low leakage Tantalum capacitor is used, this can be increased to 5 minutes or more. If the value of the timing capacitor is too high above 470 uF, charging time will be prolonged which will upset the timing cycle and the output remains high even after the desired time is over.

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LED Display Brightness Controller

Even if you are designing a microcontroller-based LED display system, often it may calls for a manual option to control brightness of the LED display unit. On the otherhand, if it is based on discrete components, such an option is a crucial requirement. Here is an economical solution for such situations. The visible brightness of an LED display can be continuously varied by applying a pulsed-signal and varying its duty cycle. Usually, almost all 7-segment decoder ICs have a blanking input (RBI) connection to imply this type of brightness control. Because, the frequency in picture is above 50 Hz, unwanted flickering effect will not be noticeable.

In the practical world, CD4033 is a very popular CMOS IC used with 7-segment LED displays. CD4033 consists of a 5-stage Johnson decade counter and an output decoder which converts the Johnson code to a 7-segment decoded output for driving one stage in a numerical display. This IC is particularly advantageous in display applications where low power dissipation and/or low package count is important. Another one is the TTL IC 74LS47 which is a BCD decoder/driver for seven segment common anode (CA) displays. Note that, the IC 74LS48 also makes the same work, but designed for seven segment common cathode (CC) displays. CD4511 is the CMOS version BCD decoder/driver for seven segment common cathode displays, with latch ability.

The solution described here is nothing but a simple add-on, built around the 555 chip (IC1) wired in ‘freerunning’ mode. Modified configuration using the 1N4148 diode (D1) provides a control over duty cycle without changing the output pulse frequency. As a consequence, the output frequency of 555 remains unaffected while its duty cycle is varied over a wide range by the 100K brightness control potetntiometer (P1). Output of the 555 IC (pin 3) can be applied to the decoder’s blanking input through the 2N2222 driver transistor (T1).

LED Display Brightness Controller Circuit Diagram:

Pointer:

According to datasheets, in CD4511, when the input of the light test (LT) is activated in LOW, regardless the values of the rest of the inputs, all the segments of the display are lit up. When the blackening input (BI) gets activated in LOW with the light test input HIGH and regardless of the values of the rest of the inputs all the segments of the display are turned off (blackened). Similarly, in 74LS4X, when the light test input (LT) is activated in LOW, all the segments (a-g) of the display are lit up. The terminal BI/RBO functions as an input or an output. It becomes an output when the input RBI is activated in LOW. When the blackening input BI is activated (LOW), the display is blackened, meaning that the outputs become OFF. By activating the RBI input (LOW), the terminal BI/RBO changes into a blackening output RBO and is turned into LOW. Note that, ‘blanking’ means none of the segments of the LED display is turned on.

Note: This is an unorthodox attempt to draw your attention to the working of 7-segment LED display driver ICs, especially their ripple blanking input/output (RBI/RBO) features. You can learn more about these less-known features by referring related articles/ tutorials/datasheets published elsewhere in this website/internet. As a bonus, you can build your own LED display brightness controller circuit using the ubiquitous 555 chip!

Author by: T.K. HAREENDRAN

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Motor Bike and Car Turning Signal Indicator with 555 Timer IC

Here is electronic circuit project for Motor Bike and Car Turning Signal Indicator. In our daily life we see vehicles turning indicators when they turn left or right. It looks like Simple LED Blinking. But it's not only simple blinking LEDs inside indicators of vehicles. Here we are building a fancy Car/Bike Turning Indicator Circuit using 555 Timer IC, with four LEDs glowing one by one in a particular pattern and we can control the speed or frequency of this LED indicator by simply turning a Potentiometer.

Motor Bike and Car Turning Signal Indicator Circuit Diagram:

Parts List:

• BC547 or MPS A42 NPN transistor -4
• Bread Board -1
• 555 Timer IC -1
• 1K -1
• 10k POT -1
• 10K -6
• 68K -1
• Power Supply
• LED -4
• 10uF Capacitor -1
• 470uF -1
• 1N4148 Diode -2
• 9V Battery -1
• Jumper wire

In this Bike Turning Signal Indicator circuit, we have used one 10K and 1K resistors and a capacitor for generating a delay. The 1n4148 diode is connected in reverse bias at the output pin of 555 timer IC to maintain a constant current. Due to base current BC547/MPS42A (NPN) Transistor drive, the LED’s ON and OFF. LEDs are connected to the transistor through a 220ohm resistor with respect to Vcc. This 220ohm resistor will save LED to may get damaged.

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False Triggering Eliminator for Timer 555

Normally, false triggering of timer IC 555 takes place during power on, resulting in unwanted output, which starts the timer’s time cycle. The circuit becomes inefficient especially when the load has to be energised only when desired. Here is a simple circuit to eliminate false triggering of timer 555.

The circuit is wired in monostable mode and grounded via N/O contact of RL(b) as well as switch S2. When power switch S1 is switched on, the circuit will not be grounded until switch S2 is momentarily pressed. To provide the triggering pulse to the timer at pin 2, press switch S2 momentarily.

False Triggering Eliminator for Timer 555

To activate the relay for operating the load, switch on the power to the circuit by pressing switch S1 and then S2 momentarily. The resulting output at pin 3 goes high and energises relay RL to operate the load. Now after momentarily pressing S2, the circuit remains on as GND gets connected to N/O contact of RL(b). At the same time, pin 2 is disconnected from N/C contact of RL(b), which prevents further triggering.

The time period of relay energisation (approximately 3 minutes) can be easily changed by changing the values of resistor R1 and capacitor C1 according to the requirement to operate the load. At the end of the cycle, the relay gets de-energised and the circuit becomes ungrounded again.

Author : Ajay Singh - Source by :EFY

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12V Power Inverter using 555 Timer

This 12V power inverter circuit is very useful when you want to use a 240 volts consumer powered by a 12 volts car battery .In contrast to the usual feedback oscillator type of inverter, the oscillator of this inverter use a 555 timer connected as an astable multivibrator that is separate from the output stage, which allows easy adjustment of the oscillator frequency to suit different applications.

This 12V power inverter circuit can be used to power small power devices that need a 240 volts .

12V Power Inverter using 555 Timer Circuit Diagram:

The output of the 555 timer drives the base of T1 and T2 transistors . The wattage of this 12 volts inverter circuit depend on the driver transistors and the output transformer used . The output of this circuit will provide a 240v at 50Hz.

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TV Remote Control Jammer

This circuit confuses the infra-red receiver in a TV. It produces a constant signal that interferes with the signal from a remote control and prevents the TV detecting a channel-change or any other command. This allows you to watch your own program without anyone changing the channel !!    The circuit is adjusted to produce a 38kHz signal. The IR diode is called an Infra-red transmitting Diode or IR emitter diode to distinguish it from a receiving diode, called an IR receiver or IR receiving diode. (A Photo diode is a receiving diode).

TV Remote Control Jammer Circuit Diagram:

There are so many IR emitters that we cannot put a generic number on the circuit to represent the type of diode. Some types include: CY85G, LD271, CQY37N (45¢), INF3850, INF3880, INF3940 (30¢). The current through the IR LED is limited to 100mA by the inclusion of the two 1N4148 diodes, as these form a constant-current arrangement when combined with the transistor and 5R6 resistor.

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False Triggering Eliminator for Timer 555

Normally, false triggering of timer IC 555 takes place during power on, resulting in unwanted output, which starts the timer’s time cycle. The circuit becomes inefficient especially when the load has to be energised only when desired. Here is a simple circuit to eliminate false triggering of timer 555.

The circuit is wired in monostable mode and grounded via N/O contact of RL(b) as well as switch S2. When power switch S1 is switched on, the circuit will not be grounded until switch S2 is momentarily pressed. To provide the triggering pulse to the timer at pin 2, press switch S2 momentarily.

False Triggering Eliminator for Timer 555 Circuit Diagram:

To activate the relay for operating the load, switch on the power to the circuit by pressing switch S1 and then S2 momentarily. The resulting output at pin 3 goes high and energises relay RL to operate the load. Now after momentarily pressing S2, the circuit remains on as GND gets connected to N/O contact of RL(b). At the same time, pin 2 is disconnected from N/C contact of RL(b), which prevents further triggering.

The time period of relay energisation (approximately 3 minutes) can be easily changed by changing the values of resistor R1 and capacitor C1 according to the requirement to operate the load. At the end of the cycle, the relay gets de-energised and the circuit becomes ungrounded again.

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Negative Ion Generator 555 Timer

This negative ion generator is a high voltage generator circuit that use a 555 timer circuit to generate square-wave pulses. The square wave pulses are applied to the Q1 transistor ( Tip120 ) that provide enough current to the Q2 (2N3055) transistor to turn it on.

Negative Ion Generator 555 Timer Circuit Diagram:

Each time when the Q2 transistor is turned on current flows through the high voltage auto-transformer, T2 ,to the a 10 kilovolt high voltage diode (D1 IMD5210). The polarity of the D1 IMD5210 diode is biased to place a negative charge on C3 and C4, leaving the discharge point negatively charged.

Voltage from  the discharge point negatively charges the air forced past it by the fan.
The output of the T1 transformer must provide 12 volts . Be careful if you want to construct this project , may be dangerous.

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Light Dependent Tone Generator 555 Timer

Here is a very simple 555 timer circuit Light dependent tone generator is presented in this circuit diagram. What is so special at this 555 timer IC project? this circuit use a LDR (light dependent resistor) to modify the frequency of the circuit.  

Light Dependent Tone Generator 555 Timer Circuit Diagram:

If the circuit is placed in a constant light the speaker will emit a sound with a constant frequency but we change the intensity of the light the circuit will generate a sound with a frequency that depends of light intensity. If the tone generator circuit is placed in a dark place the circuit don’t emit any sound.

The 555 timer IC is connected in a astable mode and the oscillation time depends of the R1, R2, C1 components value . The speaker connected at the output terminals of the circuit must have a 8 ohms impedance and a power between 0.2-0.5 watts.

The transistor used in this tone generator circuit must be BD136, 2N2905 type or equivalent .

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Open Door Alarm with 555 Timer

In this electronic circuit project Open door alarm a very simple 555 timer Open door alarm circuit project can be designed using an linear hall effect device like in this circuit diagram. This 555 timer Open door alarm circuit is based on the TL3103 linear Hall Effect device used for detecting the angle of rotation. The TL3103s are centered in the gap of a U-shaped permanent magnet.

Open Door Alarm with 555 Timer Circuit Diagram:

This type of circuit can sense the opening of a refrigerator door. When the door opens, a triac could be activated to control the inside light. The figure shows a door position alarm. When the door is opened, an LED turns on and the piezo alarm sounds for approximately 5 seconds. This door alarm electronic circuit uses a TL3019 Hall Effect device for the door sensor. This normally open switch is located in the door frame. The magnet is mounted in the door. When the door is in the closed position, the TL3019 output goes to logic low, and remains low until the door is opened.

Usually a 555 timer circuit is triggered by taking the trigger, pin 2, low which produces a high at the output, pin 3. In this configuration with the door in the closed position, the TL3019 output is held low. The trigger, pin 2, is connected to Vi the supply voltage Vcc .When the door opens, a positive high pulse is applied to control pin 5 through a 0.1 uF capacitor and also to reset pin 4. This starts the timing cycle. Both the piezo alarm and the LED visual indicator are activated.

This door alarm electronic circuit project must be powered from a 5 volt DC power supply .
The TL3019 hall effect device can be replaced with A3121EUA hall effect device manufactured by Alegro Microsystems and the 555 timer from any manufacturer should be working fine.

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Square Wave Generator with 555 Timer

This electronic project is a piece of test equipment designed using a 555 timer circuit. It's a square wave generator with 6 selectable frequencies from 1Hz to 100kHz, incrementing in decade values . This square wave generator electronic project is based on the popular 555 timer IC and generates six preset frequencies from 1Hz to 100khz. It has a wide operating voltage range and even provides visual indication of the output.

This square wave generator project is most useful as a Signal Injector for radios and TV's. A square wave is the most suitable for testing the IF (Intermediate Frequency) strip as the signal will pass through the IF transformers without any attenuation, no matter what the tuned frequency of the circuit.

Circuit Diagram:

The 555timer is configured for astable operation, meaning that it will trigger itself and free run as a multivibrator. The timing elements are resistors R1, R2 and one of the capacitors (C1-6).
For the values shown in this diagram , the six frequencies generated are 1Hz, 10Hz, 100Hz, 1khz, 10khz and 100khz.

If you want to generate a variable frequency you can replace the 68k resistor with a 100k mini trim pot , connected in series with a 10 k resistor . This square wave oscillator electronic project can be powered from a power supply that can provide an output voltage between 5 and 18 volts DC , but typically it’s recommended to use a 9 volt DC power supply .

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Electronic Alarm Project of Piezo with 555 Timer

This is a very simple Electronic Circuit Project of piezo alarm circuit. Piezo alarm which will generate a sound around 110dB can be designed using this diagram. This Piezo alarm siren circuit diagram use some common components like 555 timer ic, you can use two 555 timer circuits or one 556 circuit.

Electronic Alarm Project of Piezo with 555 Timer Circuit Diagram:

This Piezo alarm siren circuit project use two piezo sounders with high efficiency and can be powered from a wide input voltage, between 5 and 15 volts. This circuit is very easy to build, maybe you will have a little trouble with the T1 and T2 auto-transformers. Both auto-transformers used in this project are the same type and require between pin 1and 2 1500 turns of 44 SWG wire and 220 turns between 2 an 3 using 40 SWgG wire.

In this circuit the IC1:B closest to the piezo elements is set to oscillate around their resonant frequency. The frequency is then varied via input pin 11 from the other 555, IC1:A. This modulating input is a low frequency oscillation. However, instead of using the square wave output from the first 555, the step function is converted to a triangular wave by the RC network R3 & C3. The result of this is a frequency swept output which ensures that the output frequency definitely passes through the resonant frequency of the piezo elements sometime during each modulation cycle.

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Simple 40 LED Bicycle Light

How to build a 40 LED Bicycle Light Electronic circuit Project? This is a very Simple to build This electronic circuit project of 40 LED bicycle light.  The 555 circuit below is a flashing bicycle light powered with four C,D or AA cells (6 volts). Two sets of 20 LEDs will alternately flash at approximately 4.7 cycles per second using RC values shown (4.7K for R1, 150K for R2 and a 1uF capacitor). Time intervals for the two lamps are about 107 milliseconds (T1, upper LEDs) and 104 milliseconds (T2 lower LEDs). Two transistors are used to provide additional current beyond the 200 mA limit of the 555 timer.

Simple 40 LED Bicycle Light Circuit Diagram:

A single LED is placed in series with the base of the PNP transistor so that the lower 20 LEDs turn off when the 555 output goes high during the T1 time interval. The high output level of the 555 timer is 1.7 volts less than the supply voltage. Adding the LED increases the forward voltage required for the PNP transistor to about 2.7 volts so that the 1.7 volt difference from supply to the output is insufficient to turn on the transistor. Each LED is supplied with about 20 mA of current for a total of 220 mA.

The circuit should work with additional LEDs up to about 40 for each group, or 81 total. The circuit will also work with fewer LEDs so it could be assembled and tested with just 5 LEDs (two groups of two plus one) before adding the others.

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Simple 555 Amplifier

The 555 can be used as an amplifier. It operates very similar to pulse-width modulation. The component values cause the 555 to oscillate at approx 66kHz and the speaker does not respond to this high frequency.  Instead it responds to the average CD value of the modulated output and demonstrates the concept of pulse-width modulation. The chip gets very hot and is only for brief demonstrations.

Simple 555 Amplifier Circuit Diagram

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Simple Metal Detector Using 555 Timer

This metal detector electronic project schematic circuit is designed using a simple 555 timer integrated circuit . As you can see in the schematic circuit , this metal detector electronic project requires few external electronic parts . This circuit detects metal and also magnets.

Metal Detector with 555 Timer Circuit Daigram

When a magnet is brought close to the 10mH choke, the output frequency changes. This metal detector project can be powered from a power supply that can provide an output DC voltage between 6 an 12 volt . If a metal is closer to the L1 coil , will produce a change of output oscillation frequency, that will generate a sound in the 8 ohms speaker

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