DIY 555 Door Bell

Updated: Nov 21, 2018

Recently, I came across the Autodesk Circuits. It is a web based electronics design software, where you can make breadboard circuit, simulation and PCB design.I can say, it is the easiest way to learn electronics and Arduino programming.

To learn the Autodesk Circuit,I went through few of the YouTube tutorials in the Autodesk website, and found it is really simple.After spending few hours, I learned the PCB design. To test my learning, I started a simple Door Bell project based on the 555 timer .First I made the project on breadboard and then on a perforated board.After testing the prototype,finally I designed my PCB.I am really happy with the outcome.

In this tutorial, I will teach you how to make your own PCB from the Prototype.I took my 555 Door Bell circuit as an example to demonstrate the entire process. In the last step, I have attached the PCB file for this little project. You can download it.

Full Project is also available on Instructables

Step 1: Parts and Tools Required

Parts :

1. 555 Timer ( NE555N ) : Amazon

2.Electrolytic Capacitor ( 1 x 10uF and 1 x 100uF ) : Amazon

3. Ceramic Capacitor ( 3 x 10nF ) : Amazon

4. Diode ( 2 x IN4148 ) : Amazon

5. Resistor ( 4 x 47K ) : Amazon

6. Speaker ( 8 Ohm ) : Amazon

7. 9V Battery : Amazon

8. Push Button : Amazon

9. Battery Clip : Amazon

Tools :

1. Soldering Iron : Amazon

2. Nipper : Amazon

3. Desoldering Pump : Amazon

Step 2: How the Door Bell Circuit Work ?

The Door Bell Circuit is based on 555 timer in astable mode ( no stable states ).

555 timer in Astable mode :

The connection diagram of 555 timer for astable multi vibrator is shown in the above picture (fig - 3 ).

Pin 1 is grounded; pins 4 and 8 are shorted and then tied to supply +Vcc, output (VOUT is taken form pin 3; pin 2 and 6 are shorted and the connected to ground through capacitor C1, pin 7 is connected to supply + VCC through a resistor R1; and between pin 6 and 7 a resistor R2 is connected, pin 5 is grounded by a capacitor C2.

Explanation :

In the 555 block diagram ( fig -1 ) there are two comparators, one at pin -2 ( Inverting ) and other at pin -6 (Non Inverting ).

When the input voltage at pin -2 is less than 1/3 rd of the Vcc, the comparator output goes high.But as this output is hooked to Set terminal of the flip flop, the out put ( Q ) goes HIGH and complementary output ( Q comp) goes LOW. It is connected to the base of the discharge transistor, so the transistor will turned Off.

When the input voltage at pin-6 is greater than 2/3rd of the Vcc, the comparator output goes high and Reset the flip flop,the output ( Q ) becomes LOW and the complementary output goes HIGH. The discharge transistor will turned On.

Come to the external components ( fig-3 ) ,the capacitor ( C1 ) will charge through, R1 and R2. The capacitor voltage rises ,when the voltage at, pin 6, reached 2/3Vcc ( 2/3 x 9V = 6V ) , the discharge transistor turned On, and capacitor (C1) starts to discharge through R2. During discharging, the capacitor voltage will gradually falls and when it is less than 1/3rd Vcc ( 9x 1/3 =3 V ) , the output ( Q ) goes high and discharge transistor turned off. So again charging process starts,capacitor voltage rises and this process repeats again and again in cyclic manner.

Conclusion : The output is a periodic signal consists of High and Low.If you hooked a LED to this circuit, it will flash.But if you connect a speaker, it will generate a sound depending on the frequency of the out put wave.

Door Bell Circuit :

In the door bell schematic ( fig -4 ), when switch (S1) is pressed, both the diode will turned on. So pin - 4 is raised to Vcc ( neglecting the diode voltage drop ). In the block diagram, you can see a not gate is attached to the pin -4.So the 555 timer will reset.During this period only two resistors are in the capacitor( C4) circuit.( Bypassing the resistor R1 ).

So when you press the switch, charging time constant is ( R2 + R4 ) x C4 and when switch is released, the charging time constant changed to ( R1 + R2+ R4 ) x C4.

Step 3: Prototyping and Testing

For making a professional grade PCB, you have to make a prototype first. However, while you are prototyping a design, it is a very good practice to test out your design before you start getting PCBs manufactured. Every time you find something wrong with your design and have to get a new batch of PCBs made, you will be increasing costs, both in time and in money. It is far better to get the design as perfect as possible before making the PCB.

Prototyping :

1. Breadboard :

First, we will make the circuit on a Breadboard.The main advantage of a solderless breadboard is that it’s, solderless. Thus you can easily change the design just by unplugging components and leads as you need to.

2. Perforated Board:

After making the breadboard testing, I made the circuit on a Perforated Board. To make it follow the instruction below

i) First insert all the parts in to the hole of the Perforated Board

ii) Solder the all the component pads and trim the extra legs by a nipper.

iii) Connect the soldering pads by using wires as per the schematic.

iv) Use stand off to isolate the circuit from ground.

The perforated board circuit is really strong and can be deploy in a project permanently.

After testing the prototype,if everything works perfectly we can move to design the final PCB.

Autodesk circuits have a great feature of " Breadboard prototyping ".You can make the same circuit and then simulate it without using the physical parts. You do not have to install the software also.Its a web based platform.

So in the next step, we will learn it. To get started click here and sign up.

Step 4: Making the Bread Board Circuit

To make the breadboard circuit on Autodesk Circuits follow the following steps

1. Open Electronics Lab -> New Electronics Lab

2. A default breadboard will come automatically.But you can choose the desired Breadboard by clicking on the " + Components" and then search Breadboard.

3. Populate the components by searching in the components list.

4. For multiple numbers of same components, use copy ( Ctl +C ) and paste (Ctl +V ).

5. For changing the value of the components, click on the components and then change it in the dialog box.

6. Arrange the components on the Breadboard.

7. Make the circuit by using color wires.For changing the wire color, click on the wire and change it in the dialog box.

8. You can bend the wires when desired by clicking the left mouse button. For more details, you can go through the following link,

9. To simulate the circuit click on " Start Simulation ".

Note : To rotate the components use " R " on your keyboard.

Step 5: Drawing the Schematic

To draw the schematic click on the " PCB design " in the left-hand side menu bar then a new page will open

2. Click on new " New PCB Design ". 3. To add the Components , click on " + Components " on the top right corner.Then search the desired components and click on " Add "

4. Follow the same procedure to add all the components.

5. For duplicate the component use copy ( Ctl +C ) and paste (Ctl +V ).

6. For changing the value of the components, click on the components and then change it in the dialog box.

7. Arrange the Components.

8. With all of the Components added to the schematic, it’s time to wire them together.

9. By default, the schematic is an unnamed file .So it is good practice to name this file and save it.( Top left corner )

Note : To rotate the components use " R " on your keyboard.

Step 6: Making the PCB

1. After completing the schematic, switch to PCB view.This icon is located at the top right corner.

2. All of the components you added in the schematic should be there, stacked on top of each other, ready to be placed and routed.

3. The green gold lines, called airwires, connect between pins and reflect the net connections you made on the schematic.

4. Drag the components by grabbing on its pads.Then place it inside the rectangular border line.

5. Arrange all the components in such a way that the board occupies minimum space.Smaller the board size , cheaper will be the PCB manufacturing cost.

6. It will be useful if this board has some mounting holes on it so that it can bemounted in an enclosure. Now is a good time to add the holes, before we start routing the air wires.

7. After arranging the components and drilling the holes drag the border line.

8. Now you have to route.Routing is the most fun part of this entire process. It’s like solving a puzzle! Your job will be turning each of those green airwires into top ( red ) or bottom ( blue )copper traces. At the same time, you also have to make sure not to overlap two different tracks.

9. Click on " Copper Trace" and then select the track size ( power line or signal line ).Now follow the green wire path to complete the tracks.

10.Whenever you face the overlapping of the tracks, switch to the bottom layer and follow the same procedure.

11. If there is an error, a yellow spot with the error message will appear.Correct the error.

12. You can add label on any layers by hitting the " label ".

Step 7: Adding Copper Pours

Copper pours are usually a great addition to a board. They look professional . Usually, when you’re adding a copper pour it’s for the ground signal.

1. Click on the " Copper Pour " in the top left menu bar.

2. Click on any ground terminal of the components and make a border line ( dotted line ) just outside the main border.Once the path is closed it automatically pours copper to the entire board.

3.Switch to the bottom layer and follow the same procedure.

Step 8: Download the Gerber File

After making the PCB, we have to generate the files that can be sent to a PCB fabrication company that will in due course send us back some real PCB.

Generating Gerber file from PCB is pretty easy in Autodesk Circuits.

Just go to overview page and click on " Download Gerber ".

A zip folder will be downloaded.The zip folder contains 8 files

1. Bottom Copper: . gbl

2. Top Copper: .gtl

3. Bottom Soldering Masks: .gbs

4. Top Soldering Masks : .gts

5. Bottom Silk Screen: .gbo

6. Top Silk Screen: .gto

7. Drill: .drl

8.Outline: .outline

You can download my 555 Door Bell gerber file from Instructable Step-8

Step 9: PCB Manufacturing

Now it is time to find out a PCB manufacturer which can turn our gerber files to a real PCB.For maker like us OSH park, Seeed Studio and Dirty PCB are providing really good service.

For small quanity of PCB, I always prefer OSH park.They charge $5 for 3 numbers of one square inch board.

Follow the steps :

1. Go to OSH Park web site

2. Click on " Get Started Now".

3. Click on " Select a file on your Computer". Select the downloaded gerber file ( .zip ) in the earlier step.

4. Now you can give a name and some description about the project.Then click on " Continue". A new page will open, where you can find pictures related to all the gerber files discussed earlier.

5. If everything looks fine, you can place the order by clicking " approve and Order ".

Step 10: Soldering the Components

After receiving the board from PCB fab house, you have to solder the components.

For Soldering you will need a decent Soldering Iron, Solder , Nipper , Desoldering Wicks or Pump and a multimeter.

It is good practice to solder the components according to their height.Solder the lesser height components first.

You can follow the following steps to solder the components :

1. Push the component legs through their holes, and turn the PCB on its back.

2. Hold the tip of the soldering iron to the junction of the pad and the components leg.

3. Feed solder into the joint so that it flows all around the lead and covers the pad.Once it has flowed all around, move the tip away.

Congratulations !!! . Now your board is ready.

Hope you enjoyed and can make your own PCB. I am eagerly waiting for your first PCB pictures in the comment.

Thanks for reading this article. If you liked it,don't forget to share it.

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