Door Alarm

Two Parts:Gathering MaterialsBuilding the Alarm

Whether you want to protect your room from a nosy sibling or you're looking for a cheap, do-it-yourself home security system, you can easily make a loud and effective door alarm from home. Here's how to do it!Part 1 of 2: Gathering Materials

1. Go to your local hardware store and buy all the materials you'll need. Your best bet is to go to a large, name brand hardware store. Everything should be relatively cheap, probably no more than $30, depending on what you already have. You should also check your garage before you go shopping to see if you have any of the materials. Here's what you'll need:

   • Insulated wire (buy as small a spool as possible)
   • 1.5 volt battery
   • 1.5 volt mini-buzzer (if you can't find this at a hardware store they'll have one at an electronics store)
   • String (3-5 feet long)
   • Clothes pin
   • Plywood (at least 4 inches by 12 inches)
   • Glue
   • Electrical tape
   • Wire stripper or scissors
   • Removable hanging strips (optional)
   
   
2. 2
   Attach the plywood to the wall next to your door. Use removable hanging strips or tape to secure the wood on the wall. This will be the base of your door alarm.

   • Attach it close to the top of the door, about a foot from the door frame.
   • Alternatively, you can place the alarm flat on your desk or bookshelf so you don't have to hang everything.
   • If you want the alarm to be harder to deactivate, you can place it further away from the door. You can also hide the alarm or place it high on the wall where somebody can't reach it to turn it off. Where you place the alarm is up to you.
3. 3
   Cut three strands of insulated wire. Each strand should be about a foot long. If you don't have wire cutters, use scissors.

   • Try bending the wire where you're trying to cut. If scissors don't work, use a knife.
4. 4
   Strip the ends of each wire. That means you should cut off about two inches of insulation on the ends of each wire.

   • Use a scissors or wire strippers to peel off the insulation. Cut until you hit the wire on the inside, and then pull off the insulation.
   • If the insulation is difficult, use pliers or your teeth to pull of the insulation.
   
   

Part 2 of 2: Building the Alarm

1. 
   1
   Tape the battery and buzzer onto your wooden board. Use electrical tape to attach them to the wood. Place them as shown in the picture.
2. 
   2
   Wrap the stripped wire around the ends of the clothes pin. Use one end from each of your wires. Twist the stripped wire around until it's tight.

   • Make sure the wires touch when the pin is closed.
3. 
   3
   Connect another one of the stripped ends of wire to the battery. Make sure the wire is directly touching the end of the battery. Use electrical tape to keep the wire in place.
4. 
   4
   Connect the other wire from the clothes pin to the buzzer. Use electrical tape again and make sure the wire is connected directly to input on the buzzer. There should be a small opening to insert wiring.
5. 
   5
   Connect the last wire from the battery to the buzzer. Use the same method as before, making sure the copper wire is touching the metal on the battery and the metal inside the buzzer. Secure all the ends with electrical tape.
6. 
   6
   Test the switch by opening and closing the clothes pin. When the clothes pin is closed, the buzzer should turn on. If not, check the wiring again.

   • If the buzzer doesn't turn on, one of the connections of wiring is loose. That means the metal on the wire and the metal on the battery or buzzer are not touching or not touching firmly enough. Redo the connections and make sure they are firmly together.
   • To improve the connection on the battery, try this method.
   • To improve the connection on the buzzer, strip the wire more. The more copper wire exposed the more connection there is. If the buzzer has a screw to fasten the wiring, put the wire in the insert and fasten the screw to clamp the wiring in place. If there is no screw, use plenty of electrical tape.
   • Make sure the ends of stripped wire on the clothes pin are firmly touching. If they aren't or are just barely touching, wrap more wire around until the connection is strong.
   • Alternatively, you could be using a faulty battery or buzzer. Try a different battery. If that doesn't work, and you're certain your connections are strong, bring the buzzer back and get a new one. They should reimburse you for the faulty buzzer.
7. 
   7
   Place a piece of cardboard in the clothes pin to separate the wires. This will stop the buzzer from going off.

   • Any non-conductive material like paper, wood, or rubber works.
   • Your best bet is to rip off a piece of cardboard from a box. Fold it over a few times to make it thicker.
8. 8
   Glue the clothes pin to the wood. Keep the clothes pin close to the battery and buzzer.

   • Tape down any excess wiring to the wood with electrical tape.
9. 
   9
   Attach the string to the piece of cardboard between the clothes pin. Make sure the string is tied tightly to the center of the cardboard.
10. 
    10
    Tape the other end of the string to your door. Adjust the length of string and placement of the alarm so that the string is taut between the alarm and the door. When the door opens, the string should pull the cardboard out, setting off the alarm.
    
    

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Tips

• Remember to check your garage or work shed for materials before you go shopping. There's a good chance you already have most of the materials you need!
• Scissors work well for stripping wire. Cut until you hit the internal wire. Then pull the insulation using the scissors.

Warnings

• Use sensible precautions when working with electricity.
• If your alarm is for home security, don't put any part of the electrical circuit in a place where a burglar could break it. Remember, a stealthy break-in requires only for the circuit to be broken.
• Be careful when cutting and stripping the wires. Cut away from you and keep you fingers and limbs away from the knife.

Things You'll Need

• Insulated wire (2 strands)
• 1.5 volt battery
• 1.5 volt mini buzzer
• Electrical tape
• String (3-5 feet)
• Spring-type wooden clothes pin
• Piece of plywood (4 in x 12 in or greater)
• Glue
• Wire stripper or scissors
• Removable hanging strips

DOORBELL

Step 1: Gathering Tools & Materials

Materials:
NAME RANGE NO
Resistor - 100R - 1
Capacitor - 220uf/25v - 1
Transistor - BC 547 - 2
BT66T19L 1
Speaker - 4 ohm - 1
Wire ----- required
Battery - AA size - 2
Common PCB ------- required
Push Button Switch - 1
Soap Box
Plastic Bush
Small Tic Tac box
Super Glue
Battery Cap
TOOLS&EQUIPMENT
-Soldering Iron
-Soldering Wire
-Hot Glue Gun
-Wire Cutters
-Insulating Tape

Step 2: ASSEMBLING THE CIRCUIT

Mark the required size on PCB board and cut it out.
Assemble the circuit by give plan.
Solder the wire on the terminals of speaker and connect the speaker to the circuit board.

Step 3: MAKE THE COVER FOR DOORBELL

Because of choosing the Soap Box for this project, normally it contains holes on bottom this will help to spread the speaker sound.
Take the Soap Box; this contains two parts top and bottom parts.
We are going to fix the speaker on Soap Box bottom side ( hole side) by using the Glue Gun.
Mount the plastic bushes on bottom of the circuit board by the help of Super Glue.
Take the top part of the Soap Box; place the circuit board on it by the help of Super Glue.

fm transmitter

Description:
After getting several comments from young electronic students , I am rewriting this article to make the FM transmitter making process more clear.
This tutorial is for making simplest FM transmitter using one transistor. You can make this project with less components and it is an easy and simple project for beginners.
Before you proceed, please see the schematic given below. In the schematic, you will see the components required for making an FM transmitter.The transmission range of this circuit is approximately 10-20 meters.

The schematic of FM transmitter is given below:

You need the following components for this experiment:
1. Q1- Transistor- 2N3904

2. Capacitors- 4.7pF, 20pF, 0.001uF, 22nF.
Note: 0.001uF has code 102 and 22nF has code 223.
3. Variable capacitor: VC1. It is also called trimmer capacitor. You can buy one from your local store. The capacitance range should be 0-100pF or 10-100pF. If you cannot get one, try to get a trimmer capacitor that has minimum capacitance of 20pF. You can also get such capacitor from your broken radio, but you may need assistance in getting that out from your radio.

4. Resistors- 4.7 kilo Ohm, 470 Ohm
5. Condensor/ Electret Microphone

On your electret microphone, you will see that on one of the pins, there is solder pad connected to the case of microphone. Remember that pin is always negative.

6. Inductor- 0.1uF.
6-7 turns using 26 SWG wire.
You need to scrap the ends of inductor, otherwise, the inductor won’t work. Check the video given below to know how to make an inductor.

Or you can also use another inductor.
0.1uH
Learn to make an inductor for FM transmitter
7. Antenna: Use 15cm to 1 meter long wire for antenna. If you have a long antenna, the signal transmission will be better.
The following picture shows the components used for making FM transmitter. You can simply follow the steps shown below.
On the image shown below, you can notice that I have not used a trimmer/variable capacitor. I have used a fixed 20pF capacitor instead. So, if you don’t have a variable capacitor, you can use a fixed capacitor also.


Insert transistor, resistors and capacitors on breadboard. You can see the values of the components on the previous picture.

Then insert electret microphone.

NOTE: terminal touching the casing is -ve


Use 15cm long antenna. You can use a normal wire for antenna.






Then, with a non-conductive tool, adjust the capacitor for the clearest reception, rotate it till the receiver receives a sound from the microphone of transmitter. Use the following formula for determining the frequency.