I don´t have any engineering or electronics background (actually i am a surgeon), but i love to make stuff and i am self teaching electronics with the help from Google and instructables.com . This is my first instructable and English isn´t my native tongue, so bear with me please...
DISCLAIMER: If following this guide anything/anyone/yourself damages i shall not be held responsible.Do it at your own risk. Take all the safety measures (goggles, gloves, etc)
Step 1: Bill of Materials:
-0.01uF ceramic capacitors= 2
-1uF electrolitic capacitor = 1
-180 k resistor = 1
-56 k resistor= 1 (i did it on the weekend with no opened stores, so i used 47k + 10k series resistors)
-Piezo buzzer= 1 (i used a Hycom HY-07 that i took from an old modem)
-Button cell batteries= 3
-Battery holder (from a cheap-o pen/flashlight i had)
-hot glue gun
Step 2: Let the Stripping Begin..
Step 3: Test 1,2,3
I found a buzzer circuit ( http://electronic-circuits-diagrams.com/alarmsimages/alarmsckt5.shtml ) the easiest and simple circuit i could find and tried it on the breadboard. It worked out fine, except i changed de 10k resistor (pins 7 and 8 of the 555 IC) for a 180k resistor because i liked the tone better.
Step 4: Avengers Assemble
Step 5: Adding the LED, Buzzer and Switch
-The (+) leg of the LED and the pin 4 of the 555 (through the on/off switch) to the positive pole of the battery pack.
-The secondary probe (another used pen) with a wire wrapped around the tip to the negative pole of the battery pack
When the two probe tips touch each other (or through a conductive material such as a wire or a circuit track) the circuit closes and the LED lights up and the buzzer vibrates with a nice tone.
The buzzer can be turned off with the switch, while the LED still lights up with continuity.
Step 6: Mounting the Switch, the Buzzer and the Battery Holder
The buzzer and the battery holder are housed in the cap that clips on the end (that was reattached with a hole so wires can pass through and hot-glued). This allows me to change the batteries when they die.
Step 7: Continuity Tester Completed
Step 8: It�s Alive!!
You can see the LED light (obviously you can´t hear the buzzer), maybe later i upload a video.