hi all, this is my first instructable, i hope you enjoy, and if you have any questions dont hesitate to ask me either by sending me an E-mail (Ahmedyasserahmed@gmail.com) or simply comment and i will do my best to answer all of your questions.
in this instructable i will explain how to build a simple 555 circuit that will blink a led and sound a buzzer, this has many application for example you can connect an LDR between the power source and the circuit and then put it in your closet where it is dark and when someone opens the closet the alarm will sound, or connect it to a transistor LDR circuit (which i will explain how to build in another instructable) and put it next to your door so if any one passes by the LDR his shadow will cause the alarm to sound.
Materials that are required:-
1- 10 kohms resistor
2-4.7 Kohms resistor
3- 470 ohms resistor
4- 555 IC circuit
5 Jumper wires
6-LED
7-capacitor (47 uf)
8-Buzzer
9-Battery and holder (rpeferably 9v but anything between 5-12 will work)

## Step 1: Connecting the Brain

IC555 is the brain of your circuit it controls everything,we start by attaching it in the middle of the bread board

## Step 2: Connecting the Capacitor

now we need to connect our capacitor between pins one and two (make sure the negative side points towards pin 1) here i used a 47 uf capacitor you can change it but according to the capacitance the frequency of the led flashing (and the buzzer) will vary.

## Step 3: Connecting Pins 2 and 6

Now we need to connect pins two and six using a jumper wire
in a breadboard there is a gap between the 2 sides in the power supply row be sure to connect them (look at the photo)

## Step 4: Pins 4 and 8

now we connect pins 4 and 8

## Step 5: Resistors Time!

now we get the 10k resistor and connect it between pins 6 and 7

## Step 6: Next Resistor

now we connect the 4.7k resistor between pins 7 and 8

## Step 7: One Last Resistor

now we get the 470 ohms resistor ( you can also change this one but this will also affect the frequency (on the circuit board i used a 100 ohms resistor)).and we connect it one leg in ground (negative row) and the other in an empty slot

## Step 8: Connecting the Led

we connect the short leg of the led (negative leg) to the resistor and the other leg to an empty slot ( used yellow but you can change it red is good)

## Step 9: Connecting the Led to the Brain

now using jumper wires connect pin 3 of the IC to the positive leg of the led.

## Step 10: Connecting the Buzzer

we connect the buzzer parallel to the led make sure of correct polarity.

## Step 11: Feeding the Brain

We connect pin 1 to ground and pin 8 to positive.

## Step 12: Finishing Up

we connect positive to the poristive row and negative to the negative row.
And there you go attach your battery.

## Step 13: Working and Troubleshooting.

here is a video of it working if yours doesn't work please tell me and i will help you out.
if you want it to be light sensitive connect an LDR between the battery and the circuit.
Have fun
u will find the schematic attached.
<p>This works great! thanks for posting it. At first, I thought it was not working because I could not hear the 8 Ohm 0.5W speaker. Then I realized the speaker was clicking very quietly at about two clicks per second. You can either listen to the speaker or unplug the speaker and watch the LED blink at the same rate.</p>
<p>how do you make it so the led continues on blinking and so with the alarm (will continue on buzzing?) i made the circuit but the alarm only went off once, and the led blinked only once too. thanks</p>
<p>blinking depend on time constant which is tau = RC. try making tau greater than 1 second. you would be able to see the LED blink. Use 220 uF capacitor and a 100ohms resistor if you want to see the LED blink. </p>
<p>hi,</p><p>am not sure what do you mean.</p><p>do you mean that they dont blink together at the same time?</p>
<p>i am using a 5v buzzer and it doesn't buzz</p><p>just a little tic</p>
<p>Remove the buzzer and check if LED id glowing, if not try using lower capacitance value. 0.047uF worked for me </p>
Am not sure y a 5v buzzer wont buzz but could you try connecting it to a transistor
<p>im sorry but i didn't realize that i have AC buzzers :P </p><p>i tried it with DC buzzer and worked perfectly</p>
can the buzzer be replaced with 8ohm speaker?
<p>yes</p>
My led is not blinking continuosly it only blinks once pls help
My led and buzzer are not blinking continuously it only blinks once. Can you figure it out?
With some modifications :D
Shematic is last image
check the last step ;) <br>
ok i will :) <br>
<p>What spec of buzzers can be used?</p>
thanks for commenting and i hope you enjoyed
Nice. Easy to understand. Fun simple lil project. Thanks 4 posting it.
nice, <br> i did it and it totally works i added the LDR as you told us and it works perfectly