Integrated Circuits, or ICs, or Chips are lots of transistors and other components all joined together on a single piece of silicon. They are called integrated, because they have all the circuit components joined or integrated together on the chip of silicon.

And because there are many different circuits that you could design, there are many different types and designs of chips. In fact, the number is growing daily, and by now there are millions of designs.

Each design needs its on data sheet on what the circuit is inside the chip. It also needs to describe how to connect to it.

When you look at a chip, you do not how to connect to it unless you know which one it is, and you have read and understood the data sheet. Some data sheets are over 1000 pages long.

So although these devices all have a common name – chip – there are many many different types, doing lots of different functions.

The phrase - computer chip – means only a very general thing. To electronic engineers, they need to know its model number and use its data sheet to know how to design circuits around it.

The first Integrated Circuit chip we will use is called a 555 timer. We can use this chip to easily make a flashing LED. Flashing LEDs are common in lots of things from toys to phones to cars to planes.

So, how do we make something flash? We need two things – something to time how long the LED is off, and something to time how long it is on.

The 555 timer has all this circuitry inside it, integrating lots of transistors inside it to make the timers. Below is the circuit inside the chip. This is a very simple chip compared to almost all other ones these days. But it is very complicated compared to all the other circuits we have made earlier. All these components take up a space less than 1mm x 1mm. The package we connect to is much bigger to protect the chip, and make it easy to connect and solder to.

So to connect to the chip, we do not have to know all the details inside. The manufacturer of the chip gives us information on how to connect to it with examples and values.

Above is the information from the manufacturer on how to make an oscillator. We can use this circuit to make an LED flasher.

Below is a conversion of the circuit above to one we can wire using croc leads. You have to be very careful when connecting the leads to the chip, as the chip is really designed to be soldered onto a circuit board.

Make sure none of the croc leads touch each other. You can bend the legs of the chip a bit to make it easier to connect. Connect the battery last to make it safe as you wire up the rest of the circuit. Take your time..

Connect the white croc leads to the LED, capacitor and the chip. Note which leg goes where.

Connect the green croc leads to the resistors  and the chip.

Connect the two yellow leads. From the capacitor to the chip. From the resistors to the chip.

Connect the black croc leads to the battery, chip and capacitor.

Connect the red leads to the battery +, the resistors and the chip. Connect the battery last to make it safe as you wire up the rest of the circuit.

The LED will start flashing if you have connected everything correctly.

If the circuit does not work, check every lead is connected correctly.

It is very common for circuits not to work the first time  - the reason is nearly always because they have not been connected up correctly. Occasionally there is a broken component, but this is very rare.

So check your circuit carefully.

• Electricity is the flow of electric charges. In most cases with everyday circuits, this is the flow of ELECTRONS.
• Electrons are super small. If you look the word up in a good dictionary, electron will be defined as :
• A lepton with
• a negative charge of 1.6022 x 10^-19 coulomb
• Rest mass 9.1096 x 10^-31 kilogram
• Radius 2.818 x 10^-15 metre
• Spin ½

• There are an incredibly large number of electrons flowing through the wires in a second – about 100,000,000,000,000,000 or so..

• LED stands for Light Emitting Diode
• Diodes only conduct electricity in one direction.
• To connect properly, connect the positive or + side of the battery to the LONG lead of the LED.
• Directly connecting an LED across a battery can break the LED. It can get hot, and so can the battery. The LEDs used will tolerate a few seconds of direct connection. However, the circuits have been designed to use the fingers or the carbon circuit board to limit the current flowing. To minimise the number of components, extra current reducing resistors have not been used. See the web site for alternative circuits.
• Some modern LEDs are so sensitive and efficient that they will glow even from the small amount of electricity that can flow through a person using a 9volt battery
• The more electrons that are flowing through the LED, the brighter it will be.

• The transistor being used has three terminals called:
• Base
• Emitter
• Collector
• Transistors can be considered as switches or amplifiers or multipliers.
• Multipliers are probably the easiest word for most people to understand. The number of electrons flowing through the base is amplified or multiplied by the gain of the transistor. This result is then how many electrons will flow through the collector and the emitter (almost)..
• The gain of a transistor is a characteristic of each transistor, based on its fabrication style and parameters. The BC108 transistor being used has a gain of about 300. So for every electron that flow through the base, about 300 will flow though the collector/emitter part of the circuit.
• In the transistor circuits, you can see that the transistor has amplified the number of electrons flowing through your fingers or PCB, because of the difference in the brightness of the two LEDs in the circuit.