Circuit Prototyping and Fabrication
The 555 timer/oscillator integrated circuit has been around since 1971 and is the biggest selling IC in the history of the electronics industry. They are in use in many capacities from toys to spacecraft and the original design has not changed since its invention.
The 555 timer can be used in a number of modes. In this activity it will be configured as an astable multivibrator or free running oscillator. In simple terms, the chip will produce a train of electronic pulses which when connected to a speaker will produce a tone. The pitch or more precisely, the frequency of the tone, is determined by the value of the resistors and capacitor in the circuit.
PART 1: Prototype
Since the 555 timer forms the focus of this circuit place it on the proto board first. This will act as a reference to place the connecting wires. Make sure the dot which indicates pin 1 is in the position as shown in the next illustration. Also make sure it is placed in the exact location shown. Place all the wires as well.
Next insert the electronic components:
Next, double check your circuit and make sure the wires and components are exactly placed as shown. Is the dot on the 555 timer (pin1) in the bottom left corner?
If you have a Vernier Labpro or a USB Oscilloscope you can measure the frequency output and compare to the predicted value. The activity will open in a new window.
Part 2: Fabrication
In this part you will make a permanent circuit using a pre-etched and drilled printed circuit board. Start by soldering the 8 pin DIP socket. The components are mounted on the top side of the board and the pins are soldered on the "copper" side. The socket is used in case the chip "burns out" and needs to be replaced.
Next insert and solder the connecting wires. Here are a few hints:
Next insert and solder the electronic components:
Since the circuit will be used as a test device, a pair of alligator leads will be used to connect external devices. solder the leads exactly where the 100K resistor should be. Make sure the wire insulation is close to the PC board. Note: In this exercise the 100K resistor (R1) has been soldered "inline" with one of the leads. It doesn't matter which way the leads are placed.
Finally, use a cable tie to secure the alligator clip leads to the PC board. If not, the leads will eventually be pulled out of the PC board. The battery can be secured to the PC board with a piece of double sided tape. Before you connect the battery read the following hints: