Supreem Circuits Diagram and Projects: 555

555-IC Timed Beeper Circuit Diagram

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This is a simple t<b>imed beeper circuit diagram</b> of beeper using 555 timer. This circuit can be  employed to energize lights, horn, or other signaling device at any  desired interval when the mercury switch is triggered. Since the current  handling capability of mercury switch is not so high, an SCR is used to  handle current drawn by the <b>555 timer circuit</b>. Chose the SCR  current  rating of 500mA at minimum to safely drive the 555 IC and the relay. The  relay is not needed when the current drawn by alarm is less than 200mA,  in this case the alarm can be installed to directly replace the relay  coil.  Here is the schematic diagram of the circuit.</div>
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<b>555-IC Timed Beeper Circuit Diagram</b><br />
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555-IC Timed Beeper Circuit Diagram

This is a simple t imed beeper circuit diagram of beeper using 555 timer. This circuit can be employed to energize lights, horn, or othe...

Simple 555 Timer Circuit key cod

555 05:53

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A very simple electronic key code lock circuit that require few external  components can be constructed using this schematic diagram . This  electronic key code lock circuit is based on a common <b>555 timer circuit</b>  and some other common components .<br />
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This low cost key code circuit use six switches that needs to be pressed  to open the lock, but only two switches at a time. In many other , more  expensive electronic circuits the key code is formed by pressing some  switches one by one , not like in this case two switches . If you don’t  like to press two switches in the same time you can eliminate one switch  , but in that case the code can be more easy to guess by someone ells  .Thus a total of three sets of switches have to be pressed in a  particular sequence. (Of these three sets, one set is repeated.)<br />
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An essential property of this electronic code lock is that it works in  monostable mode, i.e. once triggered, the output becomes high and  remains so for a period of time, governed by the timing components,  before returning to the quiescent low state.Pin 2 of <b>555 timer</b> is the  triggering input pin which, when held below 1/3 of the supply voltage,  drives the output to high state. The threshold pin 6, when held higher  than 2/3 of the supply voltage, drives the output to low state. By  applying a low-going pulse to the reset pin 4, the output at pin 3 can  be brought to the quiescent low level. Thus the reset pin 4 should be  held high for normal operation of the IC.<br />
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Three sets of switches SA-SC, S1- S8 and S3-S4 are pressed, in that  order, to open the lock. On pressing the switches SA and SC  simultaneously, capacitor C3 charges through the potential<br />
divider comprising resistors R3 and R4, and on releasing these two  switches, capacitor C3 starts discharging through resistor R4. Capacitor  C3 and resistor R4 are so selected that it takes about five seconds to  fully discharge C3.</div>
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Depressing switches S1 and S8 in same time, within five seconds of  releasing the switches SA and SC, pulls pin 2 to ground and IC 555 is  triggered. The capacitor C1 starts charging through resistor R1. As a  result, the output (pin 3) goes high for five seconds.Within these five  seconds, switches SA and SC are to be pressed momentarily once again,  followed by the depression of last code-switch pair S3-S4.<br />
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These switches connect the relay to output pin 3 and the relay is energised.<br />
The contacts of the relay close and the solenoid pulls in the latch  (forming part of a lock) and the lock opens. The remaining switches are  connected between reset pin 4 and ground. If any one of these switches  is pressed, the IC is reset and the output goes to its quiescent low  state.</div>
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Simple 555 Timer Circuit key cod

A very simple electronic key code lock circuit that require few external components can be constructed using this schematic diagram . Thi...

Using 555 Timer - Voltage Controlled Switch

555, SWITCHS 05:39

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In this circuit the 555 timer is used in a novel way, as a voltage  controlled switch.The old and omnipresent NE555 can be very good at  something it was not meant for: driving relays or other loads up to 200  mA. The picture shows an example circuit: if the input level rises over  2/3 of the supply voltage - it will turn on the relay, and the relay  will stay on until the level at the input drops below one third of the  supply voltage.<br />
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If the relay and D1 were connected between pin 3 and ground, the relay  would be activated when the input voltage drops below one third, and  deactivated when the input voltage goes over two thirds of the supply  voltage. It is also a nice advantage that the input requires only about 1  uA, which is something bipolar transistors can't compete with. (This  high impedance input must not be left open.) A large hysteresis makes  the circuit immune to noise. The output (pin 3) can only be either high  or low (voltage-wise), and it changes its state almost instantenously,  regardless of the input signal shape.<br />
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The voltage drop across the NE555's output stage (at 35-100 mA) is  0.3-2.0 V, depending on the way the relay is connected and the exact  current it draws. D1 is absolutely vital to the safety of the integrated  circuit.</div>
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Using 555 Timer - Voltage Controlled Switch

In this circuit the 555 timer is used in a novel way, as a voltage controlled switch.The old and omnipresent NE555 can be very good at s...

Simple Ignition Timer Schematic

555 06:59

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This circuit is a tester for flywheel<span style="font-size: medium;"><b> </b></span>based  ignition systems in small aeroplane engines. Basically the same  ignition coils are also seen in other small combustion engines used  in/on mopeds and lawn mowers  in brief, engines without a battery. The  part to be tested comprises a primary coil in parallel with the contact  breaker. The timing of this contact breaker has to be adjusted  correctly.<br />
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Since the coil’s primary has a very low resistance it is difficult to  determine whether the contact breaker is open or closed.  However, you  can determine that reliably with this circuit, using an LED  and a beeper. The circuit is implemented twice because aviation engines  (Cessna, Piper and similar) always have two ignitions in parallel to  increase reliability. For two-cylinder engines, well the purpose is  obvious.<br />
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<b><span style="font-size: medium;">Ignition Timer Circuit Diagram</span></b><br />
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The circuit consists of a 555 and a few transistors. The 555 supplies a  square wave of about 3000 Hz. This signal goes to power transistors T1  and T2; these can supply quite a bit of power and are robust enough to  withstand the voltage transients from the big coils. The test connection  (K2 and K3 respectively) are connected in parallel with the contact  breaker to be tested, which itself is in parallel with the ignition  coil. The frequency of 3000 Hz is either short circuited by the contact  breaker or if the points are open  is amplified somewhat by the  resonance of the coil itself. <br />
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This allows you to reliably detect  the difference bet ween a closed and open contact breaker, despite the  low resistance of the coil, which is in parallel with it. When the  contact breaker is open the amplified pulses will turn on T3 and T4  respectively, so that the relevant LEDs turn on and the buzzer will  sound.<br />
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The components are not critical, but do use a sensitive  type for the piezo buzzer. The power supply is 3 V (2 times AA or AAA  batteries).</div>
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Simple Ignition Timer Schematic

This circuit is a tester for flywheel based ignition systems in small aeroplane engines. Basically the same ignition coils are also se...

Long Duration Timer using ATtiny2313

555 05:32

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This timer circuit is designed to switch on a 12 V load in a  solar-powered installation for a preset period at the press of a button.  When the period has expired a latching relay disconnects both the load  and the controller circuit from the 12 V supply. The length of the  period can be configured by making suitable changes to the  microcontroller’s source code.<br />
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<a href="http://3.bp.blogspot.com/-Jsj6VFNiAa8/URFdbR_OH3I/AAAAAAAAL8Y/KzjpNwizTCA/s1600/Long+Duration+Timer+Software.png" style="margin-left: 1em; margin-right: 1em;"><img alt="Software" border="0" src="http://3.bp.blogspot.com/-Jsj6VFNiAa8/URFdbR_OH3I/AAAAAAAAL8Y/KzjpNwizTCA/s1600/Long+Duration+Timer+Software.png" title="Long Duration Timer Software" /></a></div>
When button S1 is pressed a voltage appears across relay coil L1, and  the relay switches the load on. Since the relay is a latching type, it  remains in this state when the but ton is released. There is now a  supply to the 78L05 voltage regulator (a low-dropout type such as the  LP2950CZ-5.0 may also be used) and the microcontroller is powered up. In  the microcontroller the timer program runs until the configured time  interval has elapsed. Around 90 % of the way through the time period LED  D2 lights as a warning that the load will shortly be switched off, and  this time can also of course be configured by changing the software.<br />
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When the full time interval has elapsed the microcontroller sets an  output (pin 7) high, which triggers the CNY 17-3 optocoupler and in turn  drives relay coil L2. The relay returns to its initial state,  disconnecting the load as well as the controller (which is also powered  via the relay contact) from the 12 V supply.<br />
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<b><span style="font-size: medium;">Long Duration Timer Circuit Diagram</span></b><br />
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The author used a miniature 16 -by-2 LCD panel type HMC16223SG in his  prototype, measuring just 52 mm by 20 mm. It is of course possible to  use any standard LCD module that uses an HD44780-compatible controller.  Note that P1 is used to adjust the contrast of the LCD: if the display  appears blank it is worth checking the contrast set-ting before  suspecting a more serious problem! If desired, the LCD can be dispensed  with, along with the corresponding parts of the source code.<br />
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The upper line of the LCD shows the total time period, in seconds, for  which the soft-ware is configured, while the lower line shows the time,  in seconds, since the button was pressed.<br />
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The screendump shows the LCD settings under BASCOM-AVR. The source code for the program is available for <b><a href="http://www.elektor.com/080584" rel="nofollow" target="_blank">download</a></b><span style="font-size: medium;">. <a href="http://www.circuitsproject.com/" target="_blank">Link</a></span></div>

Long Duration Timer using ATtiny2313

This timer circuit is designed to switch on a 12 V load in a solar-powered installation for a preset period at the press of a button. Whe...

Simple Police Siren

555, Audio 23:23

Simple Police Siren

The simple Police Siren circuit uses two 555's to produce an up-down wailing sound. The first 555 is wired as a low-frequency oscilla...

Touch Switch II

555, SWITCHS 02:56

Touch Switch II

This circuit uses a 555 timer as the bases of the touch switch. You can learn more about 555 timers in the Learning section on my site. ...

Visitor Alarm Circuit Diagram Using IC 555

555, Alarm and Security 00:30

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<b><br /></b> <b>Description</b><br />
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                  Figure shows the circuit diagram of the 'Visitor  Alarm' . Here I have used a LDR and a mono stable Multi Vibrator for  making this circuit . When who breaking the LED ray, the LDR has high  resistance so the transistor will be OFF and the pin number two of the  IC 555 is negative then the IC 555 will be triggering so the output is  ON. When who don't breaking the LED ray, the LDR has low resistance so  the transistor will be ON and the pin number two of the IC 555 is  positive after that the IC 555 doesn't triggering so the output is OFF.</div>
<a href="http://www.blogger.com/blogger.g?blogID=6157106112802119563" name="more"></a><b><br /></b> <b>Circuit Idea</b><br />
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<b><br /></b><b>Making Of LDR and LED</b><br />
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           Cover both items with a black insulation tape. See the below images for further details. <br />
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LDR</center>
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<b>Arrangement Of LDR and LED</b><br />
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<b><br /></b> <b><br /></b> <b>Parts List </b><br />
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<tr><td>Component No:</td><td>Value</td></tr>
<tr><td>R1</td><td>10K</td></tr>
<tr><td>R2</td><td>10K</td></tr>
<tr><td>R3</td><td>680R</td></tr>
<tr><td>R4</td><td>10K</td></tr>
<tr><td>C1</td><td>10MF</td></tr>
<tr><td>C2</td><td>103pF</td></tr>
<tr><td>Q1</td><td>BC548</td></tr>
<tr><td>D1</td><td>White LED Or LASER</td></tr>
<tr><td><br /></td><td>LDR</td></tr>
<tr><td>U1</td><td>NE555</td></tr>
<tr><td>B1</td><td>6V Buzzer</td></tr>
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Visitor Alarm Circuit Diagram Using IC 555

Description Figure shows the circuit diagram of the 'Visitor Alarm' . Here I have used a LDR an...

Police Lights associate crystal rectifier Project

555, LED 10:25

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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. <br />
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<b>Schematic</b><br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg5RIrrca7dApdgYxRcXNWZp2AYnRhms27O3xw42tti2KX2nHf48VBsXo7gK63MU8V80KLwR_vLswatlY4V6qAZl8smZBymzTO1m9duZaAg4BwZ5oXm8EQPGe_1i8FmCT4Fjc2z08vonqY/s1600/circuit-police-lights.gif" style="margin-left: 1em; margin-right: 1em;"><img alt="Police Lights and LED Project" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg5RIrrca7dApdgYxRcXNWZp2AYnRhms27O3xw42tti2KX2nHf48VBsXo7gK63MU8V80KLwR_vLswatlY4V6qAZl8smZBymzTO1m9duZaAg4BwZ5oXm8EQPGe_1i8FmCT4Fjc2z08vonqY/s1600/circuit-police-lights.gif" title="Police Lights and LED Project" /></a><br />
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<b>Parts List</b> <br />
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1x - NE555 Bipolar Timer<br />
1x - 4017 Decoded Decade<br />
6x - 1N4148 Diode<br />
1x - 1K Resistor (1/4W)<br />
1x - 22K Resistor (1/4W)<br />
2x - 4.7K Resistor (1/4W)<br />
6x - 470 Resistor (1/4W)<br />
1x - 2.2µF Electrolytic Capacitor (16V)<br />
2x - BC547 NPN Transistor<br />
2x - LED (Blue)<br />
2x - LED (Red)<br />
1x - 9V Voltage Battery </div>
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<a href="http://streampowers.blogspot.com/2012/08/police-lights-associate-crystal.html" target="_blank">Streampowers </a></div>
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Police Lights associate crystal rectifier Project

This circuit uses a 555 timer that is setup to each runn in associate Astable operative mode. This generates a nonstop output via Pin...

IC 555 Design Note

555, Projects 12:37

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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.<br />
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<b>555 IC pin functions</b><br />
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Pin1 Ground<br />
Pin2 Trigger<br />
Pin3 Output<br />
Pin 4 Reset<br />
Pin 5 Control voltage<br />
Pin 6 Threshold<br />
Pin 7 Discharge<br />
Pin 8 Vcc<br />
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<b>Functional aspects of pins</b><br />
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<b>Trigger Pin 2</b><br />
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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.<br />
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<b>Reset pin 4</b><br />
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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.<br />
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<b>Control Voltage pin 5</b><br />
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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.<br />
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<b>Threshold pin 6 and Discharge pin 7</b><br />
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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.<br />
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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.<br />
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<b>How to eliminate false triggering?</b><br />
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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.</div>
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<span style="font-size: xx-small;"><b>555 Monostable circuit </b></span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj-XcyZtwf6WZ7cUXQ7o_W47GZ_It_f3EA8MyjS8qRIgAjpQb-eqblGpsHkIxXABwsJVXi52rOAn_j7bFOR_sG3OZqEdz51W2wlHwO10afFHlpwn4bpR4BPxGKB0aTsK-Mu-36ELCe0y4o/s1600/555-Monostable-550x363.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj-XcyZtwf6WZ7cUXQ7o_W47GZ_It_f3EA8MyjS8qRIgAjpQb-eqblGpsHkIxXABwsJVXi52rOAn_j7bFOR_sG3OZqEdz51W2wlHwO10afFHlpwn4bpR4BPxGKB0aTsK-Mu-36ELCe0y4o/s1600/555-Monostable-550x363.gif" /></a></div>
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<b>A ready recknor to select timing resistor and capacitor</b><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjmv9sC5C48B1OxQWgPG804bjCNJhWxC27dbBBYngLugpepL-MI6P31KaS8Pbv6wYRMPYxlxJpgNR6MBkmEstFpFc80tFaToquFcfP59QlZbdhAS4cB19u1BRX8YmF0bBy1YUueUlmyOJg/s1600/MONOSTABLE-TIMING.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjmv9sC5C48B1OxQWgPG804bjCNJhWxC27dbBBYngLugpepL-MI6P31KaS8Pbv6wYRMPYxlxJpgNR6MBkmEstFpFc80tFaToquFcfP59QlZbdhAS4cB19u1BRX8YmF0bBy1YUueUlmyOJg/s1600/MONOSTABLE-TIMING.jpg" /></a></div>
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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.</div>
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<a href="http://streampowers.blogspot.com/2012/08/ic-555-design-note.html" target="_blank">Streampowers </a></div>
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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 f...

Simple Water Sensor Circuit Diagram using IC 555

555, Alarm and Security 00:04

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This is a water sensor /rain alarm circuit diagram; it can be used on motorcycle, car or other device that we want to protect from water, rain. This is a simple water sensor/rain alarm circuit that makes an alarm when water/rain falls on its sensor. This circuit is based on NE555/LM555 IC and two transistors (Q1&Q2). For  transistor Q1- BC547 or BC107 and for Q2-  2N825,BC548 or BC168 can be used in the circuit. </div>
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This rain detector circuit can be supplied from voltage source of +9V-12V DC. The resistor 470K ohm is a POT/Variable resistor; it is used to adjust the sensitivity of water/rain sensor. Use a 8 ohm,0.5w-1W  speaker to hearing  better alarm. Less than 8 ohm speaker could be harmful for the IC 555. </div>
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<b>Circuit Diagram of Water Sensor </b><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgtrnF7MIo_g70oIG0AFvdNrxAXJ6KL2NYcihyphenhyphen4UaNssB6x-YeUhRoTXQs-1iwiCtB6-R5YIJJPhKuBebMGZYCg8htA1eIEjAp9c3ZAgpuYbnSo3xoVpie6Yn8Vx8E6vKJc54lpqqeVzKeq/s1600/Water-Sensor-Rain-alarm-circuit-diagram.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img alt="Simple Water Sensor Circuit Diagram using IC 555" border="0" height="273" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgtrnF7MIo_g70oIG0AFvdNrxAXJ6KL2NYcihyphenhyphen4UaNssB6x-YeUhRoTXQs-1iwiCtB6-R5YIJJPhKuBebMGZYCg8htA1eIEjAp9c3ZAgpuYbnSo3xoVpie6Yn8Vx8E6vKJc54lpqqeVzKeq/s400/Water-Sensor-Rain-alarm-circuit-diagram.png" title="Simple Water Sensor Circuit Diagram using IC 555" width="400" /></a></div>
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 We can make the water sensor as shown in the image (Fig-1) using aluminu<span style="font-family: "Calibri","sans-serif";">m conductor like a naked wire </span>. Here can be used other conductor but we suggesting to use aluminum.<br />
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Sourced By: <a href="http://www.circuitsstream.blogspot.com/" target="_blank">Circuitsstream </a></div>
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Simple Water Sensor Circuit Diagram using IC 555

This is a water sensor /rain alarm circuit diagram; it can be used on motorcycle, car or other device that we want to protect from water, ...

40 LED Bicycle Light

555, LED 01:26

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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. 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.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgjeZMxlpWDkx02L6ExR4_w0KMVI5wDYKirDEYBc748YfDP2vBEeCuRzW83qPnH9K5nnoB4DpuUFoGhqJCbN9ifms-zCc8StdOriw2xv6A-539CYqrToJ7zZ_sahnHwpvqFmVK-vakK_Gc/s1600/555leds.gif" style="margin-left: 1em; margin-right: 1em;"><img alt="Circuit  Project: 40 LED Bicycle Light" border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgjeZMxlpWDkx02L6ExR4_w0KMVI5wDYKirDEYBc748YfDP2vBEeCuRzW83qPnH9K5nnoB4DpuUFoGhqJCbN9ifms-zCc8StdOriw2xv6A-539CYqrToJ7zZ_sahnHwpvqFmVK-vakK_Gc/s1600/555leds.gif" title="Circuit  Project: 40 LED Bicycle Light" /></a><br />
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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 20mA of current for a  total of 220mA. 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.</div>
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<span style="font-size: 18px;">Circuit Source: DIY Electronics Projects </span></div>
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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 alternatel...

555 Timer - Frequency and Duty Cycle Calculator

555, LED 04:36

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Enter values for R1, R2, and C and press the calculate button to solve for positive time interval (T1) and negative time interval (T2). For example, a 10K resistor (R1) and 100K (R2) and 0.1 uF capacitor will produce output time intervals of 7.62 mS positive (T1) and 6.93 mS negative (T2). The frequency will be about 70 Hz. R1 should be greater than 1K and C should be greater than .0005 uF. Scroll down page for basic 555 information (pinout and two basic circuits).<br />
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<b>Positive Time Interval (T1) = 0.693 * (R1+R2) * C <br />Negative Time Interval (T2) = 0.693 * R2 * C <br />Frequency                   = 1.44 / ( (R1+R2+R2) * C)  </b></div>
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First introduced by the Signetics Corporation as the SE555/NE555 about 1971.Pin connections and functions: (See schematic below for basic circuits)</div>
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<b>Pin 1 (Ground)  </b>  - The ground (or common) pin is the most-negative supply potential of the device, which is normally connected to circuit common when operated from positive supply voltages.</div>
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<b>Pin 2 (Trigger)</b>   - This pin is the input which causes the output to go high and beginthe timing cycle. Triggering occurs when the trigger input movesfrom a voltage above 2/3 of the supply voltage to a voltage below1/3 of the supply. For example using a 12 volt supply, the triggerinput voltage must start from above 8 volts and move down to avoltage below 4 volts to begin the timing cycle. The action islevel sensitive and the trigger voltage may move very slowly. Toavoid retriggering, the trigger voltage must return to a voltageabove 1/3 of the supply before the end of the timing cycle in themonostable mode. Trigger input current is about 0.5 microamps.</div>
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<b>Pin 3 (Output)</b>    - The output pin of the 555 moves to a high level of 1.7 volts less than the supply voltage when the timing cycle begins. The output returns to a low level near 0 at the end of the cycle. Maximum current from the output at either low or high levels is approximately 200 mA.</div>
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<b>Pin 4 (Reset):</b>    - A low logic level on this pin resets the timer and returns the output to a low state. It is normally connected to the + supply line if not used.</div>
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<b>Pin 5 (Control)</b>   - This pin allows changing the triggering and threshold voltages by applying an external voltage. When the timer is operating in the a stable or oscillating mode, this input could be used to alter or frequency modulate the output. If not in use, it is recommended installing a small capacitor from pin 5 to ground to avoid possible false or erratic triggering from noise effects.</div>
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<b>Pin 6 (Threshold)</b> - Pin 6 is used to reset the latch and cause the output to go low.Reset occurs when the voltage on this pin moves from a voltage below 1/3 of the supply to a voltage above 2/3 of the supply.The action is level sensitive and can move slowly similar to the trigger voltage.</div>
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<b>Pin 7 (Discharge)</b> - This pin is an open collector output which is in phase with the main output on pin 3 and has similar current sinking capability.</div>
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<b>Pin 8 (V +) </b>      - This is the positive supply voltage terminal of the 555 timer IC.Supply-voltage operating range  is +4.5 volts (minimum) to +16volts (maximum).</div>
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The pin connections for the 556 which is a dual 555 timer (2 in one package) areshown in table below. For example, the two outputs for the two timers of the 556 areon pins 5 and 9 which correspond to the output pin 3 of the 555. </div>
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555      556 timer #1        timer #2</div>
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Ground         1                  7               7 </div>
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Trigger        2                  6               8</div>
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Output         3                  5               9</div>
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Reset          4                  4               10</div>
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Control        5                  3               11</div>
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Threshold      6                  2               12</div>
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Discharge      7                  1               13+ </div>
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Power Vcc    8                  14              14</div>
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The schematics below show the two basic circuits for the 555 timer. </div>
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Below is a pictorial view of the 555 timer wired as a LED flasher and powered with a 9 volt battery. The LED will turn on during time T1 and off during time T2.<br />
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<img src="http://www.bowdenshobbycircuits.info/555led.gif" /><br />
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The 555 circuit below is a flashing bicycle light powered with three C or D cells (4.5 volts). The two flashlight lamps will alternately flash at a approximate 1.5 second cycle rate. Using a 4.7K resistor for R1 and a 100K resistor for R2 and a 4.7uF capacitor, the time intervals for the two lamps are 341 milliseconds (T1, upper lamp) and 326 milliseconds (T2 lower lamp). The lamps are driven by transistors to provide additional current beyond the 200 mA limit of the 555 timer. A 2N2905 PNP and a 2N3053 NPN could be used for lamps requiring 500 mA or less. For additional current, a TIP29 NPN and TIP30 PNP could be used up to 1 amp. A PR3 is a 4.5 volt, 500 mA flashlight bulb. Two diodes are placed in series with the PNP transistor base so that the lower lamp turns 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 two diodes increases the forward voltage required for the PNP transistor to about  2.1 volts so that the 1.7 volt difference from supply to the output is not enough to turn on the transistor. You can also use an LED in place of the two diodes as shown in the lower schematic.<br />
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<a href="http://www.risecircuits.blogspot.com/" target="_blank"><img src="http://www.bowdenshobbycircuits.info/555light.gif" /></a><br />
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555 Timer - Frequency and Duty Cycle Calculator

Enter values for R1, R2, and C and press the calculate button to solve for positive time interval (T1) and negative time interval (T2). Fo...

Extend Timer Range For The 555 Circuit Diagram

555 04:44

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Anyone  who has designed circuits using the 555 timer chip will, at some  time  have wished that it could be programmed for longer timing periods.   Timing periods greater than a few minutes are difficult to achieve   because component leakage currents in large timing capacitors become   significant. There is however no reason to opt for a purely digital   solution just yet. The circuit shown here uses a 555 timer in the design   but nevertheless achieves a timing interval of up to an hour! The  trick  here is to feed the timing capacitor not with a constant voltage  but  with a pulsed dc voltage. The pulses are derived from the un  smoothed  low voltage output of the power supply bridge rectifier.<br />
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<b>Extend Timer Range For The 555 Circuit Diagram</b></h3>
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The   power supply output is not referenced to earth potential and the   pulsing full wave rectified signal is fed to the base of T1 via resistor   R1. A 100-Hz square wave signal is produced on the collector of T1 as   the transistor switches. The positive half of this waveform charges up   the timing capacitor C1 via D2 and P1. Diode D2 prevents the charge on   C1 from discharging through T1 when the square wave signal goes low.   Push-button S1 is used to start the timing period. This method of   charging uses relatively low component values for P1 (2.2 MΩ) and C1   (100 to 200 µF) but achieves timing periods of up to an hour which is   much longer than a standard 555 circuit configuration.<br />
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Extend Timer Range For The 555 Circuit Diagram

Anyone who has designed circuits using the 555 timer chip will, at some time have wished that it could be programmed for longer tim...

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