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How To Make A Simple Piezo Doorbell - Duration Adjustable - Project#1 Electronics Learning Board

Picture of How To Make A Simple Piezo Doorbell - Duration Adjustable - Project#1 Electronics Learning Board
Hi Everyone!
I've been working very hard to make electronic block tutorials for my youtube subscriberes, as well as potential buyers of my electronics learning board.  The board has many different blocks, and there are 11x tutorial videos that I have to show you how each of them work. Each tutorial has a theory and lab section, so that the user can work through the theory, and witness the result!  This is a VERY simple, and introductory circuit.  The upcoming instructables will get more complicated, and MUCH more interesting!

This project is the first of twenty (Minimum) that this project board is capable of.   You can take the tutorial information learned in this instructable, and put it to use on your breadboard!  We will be discussing the 7805 5v regulator IC, the 555 Timer based monostable multivibrator circuit, and finally, a transistor based piezo buzzer driver circuit.  By using these three blocks, you will be able to create a buzzer doorbell that is activated by a button.  You can change the duration of the doorbell by adjusting the values of passive components (A resistor and a capacitor) on the 555 timer monostable circuit.  Each clock listed in this instructable will help you to create the following circuit.  I demonstrate on the learning board, but you can do it all on your own with a breadboard!

 
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Step 1: The 7805 5v regulator

Picture of The 7805 5v regulator
Our digital circuitry may very well be sensitive to over-voltage.  While the 555 timer circuit can handle a power supply of 5v, the 5v piezo buzzer cannot.  Most projects like this would require a 9v battery.  How to we easily regulate down to 5v?  Easily!  With the help of our trusty and inexpensive friend, the 7805 5v regulator IC.  This IC has an input port (1), a ground port (2), and a regulated output port (3).  The power supply circuit, including the 7805 is talked about in depth in the below video!  In order to regulate down to 5v, you need at least 7VDC at the input pin.  If after watching this video, you have any questions, please do not hesitate to post them below!  I'll do my best to answer!

Step 2: The 555 Timer In Monostable Mode (Adjust Pulse Duration)

Picture of The 555 Timer In Monostable Mode (Adjust Pulse Duration)
Next, we have our 555 timer circuit.  To set up a 555 timer based monostable multivibrator, you need to take the steps outlined in the video below.  Remember, our power supply line (VCC) is 5v in this case, as our input power supply is regulated down to 5v.   You can adjust the pulse width of the output by adjusting the values of the timing resistor and the timing capacitor.  There is also a power-on-reset circuit that is employed so that upon power on, no false triggering occurs.  It is an easy to follow video, when many examples, and I also show you examples on a breadboard.  The schematic in the picture is not complete. The triggering circuitry is not included, but if you watch the video, you will see the schematic in full, with full explanations.  This circuit will be used to drive our piezo buzzer circuit, which is driven to full potential by a transistor driver.  Please see the next step.



Step 3: The Piezo Buzzer Driver Circuit

Picture of The Piezo Buzzer Driver Circuit
While the 555 timer can easily output enough current to properly drive our Piezo buzzer on its own, many chips cannot.  In this case, you can use a transistor driver.  In the video below, you will not only see how you can drive a buzzer to full potential, but how to drive relays, motors, and speakers with a transistor driver.  In this case, we employ the trust 2N2222 NPN transistor.

The piezo buzzer is an "active" buzzer.  Many buzzers require a an applied frequency within the audio range to operate properly.  Active buzzers simply need a power supply to be added, as there is an internal oscillator circuit that power up when 5v is applied.  The transistor driver acts to complete the circuit when power is applied from the output of the 555 timer to the base of the transistor through a protective resistor.  If this happens, then current from the collector of the transistor can flow through to the emitter, which is connected to the ground line.  If you watch the video below, this will be explained in full.

Once you've watched the video, you should be able to use all three blocks to create your own doorbell circuit!  With ease!  On your breadboard!


Step 4: Questions // The Learning Board

Picture of Questions // The Learning Board
By now, you should be able to do this on your own!  It is a simple, yet introductory circuit, and I hope that you've been able to learn something.  If after you've watched the videos, and you've created this circuit on a prototyping board, or a breadboard, and you do not get the result that you wanted, talk to me.  I'll try to help you to figure out what is going on!

We can also be reached through:
http://www.engineeringshock.com
http://www.electroniclessons.com
http://www.paintballprops.com

I created this learning board so that users can watch the block electronics videos to learn how the electronics work.  It is a practical board, and while I'd like to interest you, I don't want for you to think that this is merely a promotional add.  I want for you, the user, to be able to use the tutorial blocks to create your own circuitry.  The learning board merely acts to save time relative to setting all of the circuits out on a breadboard.  The below video shows you some of the other project examples that can be achieved with this learning board!

Pre-Order (If you are interested): http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=171081822708


The following projects will be supported, and I will be making instructables for each of them as time goes on.
1) PIR Motion Detector (Buzzer)
2) Simple Doorbell (Mono button to buzzer)
3) Turn on a relay for a short duration with a switch
4) Triggering a relay with audio (clap circuit)
5) Sensitive Laser Circuit
6) Simple Laser Detector
7) Drive a 7-segment display
8) Counting Claps
9) IR receiver motor driver
10) Vibration Detector - Vibrator to comparator (Output low) to transistor driver buzzer
11) Light Sensor Circuit
12) Touch Sensor (wire to amplifier to monostable to buzzer)
13) Relay Toggling Circuit
14) Frequency Division - Astable 555 to counter (A/B/C/D) to motor driving transistor (speaker to motor output)
15) Laser alarm system (sensitive laser cirucit - amplifier/comparator to monostable to counter toggle to buzzer driver
16) Earthquake detector (vibrator to comparator output low to monostable to counter toggler to LED
17) Quick and dirty Audio amplifier (mic to amplifier to transistor driver to motor output (Speaker)
18) Infrared toggler
19) Audi transfer through Lasers
20) Reed Switch Delay + Toggler