THE FIRST COMPUTER EVER BUILT

In pictures: Transistor history 

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Early computers, such as the ENIAC, used vacuum tubes - similar to light bulbs - to do calculations and took several people to operate

Vacuum tubes were replaced by transistors - a type of electronic switch - invented by William Shockley, John Bardeen and Walter Brattain at Bell Labs.

The first working transistor was shown off just before Christmas in 1947, but was only revealed to the public six months later.

In 1965 the Intel co-founder Gordon Moore, writing in Electronics magazine, correctly predicted that the number of transistors on a chip would double every year.

MAKING A LIGHT / DARK SENSOR

MAKING A LIGHT / DARK SENSOR

  Above is a simple light/ dark sensor. This can be connected as an input or switch to another circuit. The sensors has three green wires (1, 2 and 3). Wire 2 should always be connected to one of the inputs. If wire 1 is also connected then the sensor acts as a dark sensor. If wires 2 and 3 are connected to the inputs then sensor operates as a light sensor.The preset resistor allows the person using the circuit to alter its sensitivity to light/dark.

CONSTRUCTING A CIRCUIT USING SIMULATION SOFTWARE
	All circuits are drawn on software such as Crocodile Clips. Using this software the individual components can be joined together on the screen. Once the circuit is drawn its operation can be simulated to see if it works. If it fails it can be corrected on the computer screen and tested again. Using software to test circuit designs saves time as there is no need to physically solder together components. It also saves money as components and materials are not wasted on failed circuits
The circuit is then made into a PCB (Printed Circuit Board). Components are added and soldered in position (See PCB Section of this website). Two views of the same circuit are shown below. How do they differ?