Metronome Generator using NE555

Here is a simple circuit using IC NE555 which will be used to generate metronomes.Such a circuit is incredibly helpful to people who learns music. The circuit is nothing however an astable multivibrator wired around NE555 .The elements|parts R1,R2&C1 determines the output frequency.

Notes.

• The circuit can be wired on a general purpose PCB or common board.
• The circuit can be powered from a 9V PP3 battery.
• The POT R1 can be used to adjust the rhythm of the sound.
• The POT R2 can be used as volume control.
• The speaker k1 can be a n 8 Ohm tweeter.

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LED flasher Circuit using NE555

This is a LED flasher Circuit using NE555. This schema consumes more power, but its advantage is when you need a variable flash rate, like for strobe diagram. You can actually use this schema as a remote control for strobes that have a remote input. Of course, it has many other applications besides strobes.

• R1, R2, C1 and the supply voltage determine the flash rate. Using a regulated power supply will do much to insure a stable flash rate. For a variable flash rate, replace R1 with a 1 megohm pot in series with a 22k resistor.
• The duty cycle of the schema (the percentage of the time LED 1 is on to the time it is off during each cycle) is deterimed by the ratio of R1 to R2. If the value of R1 is low in relationship to R2, the duty cycle will be near 50 percent. If you use both LEDs, you will probably want a 50 percent duty cycle. On the other hand, if R2 is low compared to R1, the duty cycle will be less than 50 percent. This is useful to conserve battery life, or to produce a strobe type effect, when only LED1 is used.
• The NE555 timer chip can be damaged by reverse polarity voltage being applied to it. You can make the schema goof proof by placing a diode in series with one of the supply leads.
• The purpose of R3 and R4 is to limit current through the LEDs to the maximum they can handle (usually 20 milliamps). You should select the value of these according to the supply voltage. 470 ohms works well with a supply voltage of 9-12 volts. You will need to reduce the value for lower supply voltages.
• Rainbow Kits offers several kits to build the above schema. You can also order these kits from RadioShack.com. The Radio Shack catalog numbers (and web pages) are as follows: standard kit with two 5mm red LEDs, (990-0067), kit with two red, two green and two yellow 3mm LEDs, (990-0063), kit with jumbo green LEDs, (990-0048), kit with jumbo red LEDs, (990-0049). You can also buy all the parts to build the schema at your local Radio Shack store, including a schema board (276-159B).

I have built a miniature strobe schema as follows. Use a 250k pot in series with a 4.7k resistor for R1. The 4.7k resistor sets the upper flash rate limit. Use 2.2k for R2. That sets a really short duty cycle. For this schema, you dont use LED 2 or R4. For LED 1, I used a two Radio Shack white LEDs in series and no R-3. The schema runs on a 9 v battery.

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NE555 IC Timer

The 555 Timer is an integrated circuit (chip) implementing a variety of timer and multivibrator applications. The IC was designed and invented by Hans R. Camenzind. It was designed in 1970 and introduced in 1971 by Signetics (later acquired by Philips). The original name was the SE555/NE555 and was called "The IC Time Machine".

The 555 gets its name from the three 5-k Ohm resistors used in typical early implementations. It is still in wide use, thanks to its ease of use, low price and good stability. As of 2003[update], 1 billion units are manufactured every year.

The 555 timer is one of the most popular and versatile integrated circuits ever produced. It includes 23 transistors, 2 diodes and 16 resistors on a silicon chip installed in an 8-pin mini dual-in-line package (DIP-8).

The 555 has three operating modes:

* Monostable mode: in this mode, the 555 functions as a "one-shot". Applications include timers, missing pulse detection, bouncefree switches, touch switches, Frequency Divider,Capacitance Measurement, Pulse Width Modulation (PWM) etc

* Astable - Free Running mode: the 555 can operate as an oscillator. Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse position modulation, etc.

* Bistable mode or Schmitt trigger: the 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is used. Uses include bouncefree latched switches, etc.

The connection of the pins is as follows:

Nr. Name Purpose

1 GND Ground, low level (0V)

2 TR A short pulse high → low on the trigger starts the timer

3 Q During a timing interval, the output stays at +VCC

4 R A timing interval can be interrupted by applying a reset pulse to low (0V)

5 CV Control voltage allows access to the internal voltage divider (2/3 VCC)

6 THR The threshold at which the interval ends (it ends if U.thr → 2/3 VCC)

7 DIS Connected to a capacitor whose discharge time will influence the timing interval

8 V+, VCC The positive supply voltage which must be between 3 and 15 V

In the astable mode, the high time from each pulse is given by

high = 0.693.(R1 + R2).C

and the low time from each pulse is given by

low = 0.693.R2.C

where R1 and R2 are the values of the resistors in ohms and C is the value of the capacitor in farads.

Specifications

These specifications apply to the NE555. Other 555 timers can have better specifications depending on the grade (military, medical, etc).

* Supply voltage (VCC) 4.5 to 15 V

* Supply current (VCC = +5 V) 3 to 6 mA

* Supply current (VCC = +15 V) 10 to 15 mA

* Output current (maximum) 200 mA

* Power dissipation 600 mW

* Operating temperature 0 to 70 °C

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