The Famous NE555 Timer-IC, Original and a Bit Larger

Integrated circuits (IC) are indispensable today. They're made up of many thousands of electronic components (transistors, diodes, resistors, etc.) and still don't take up much more space than a fingernail. One of the most well-known ICs is the NE555 timer chip.

The NE555 integrated circuit is an active electronic device that turns an output on or off under certain conditions. It is very suitable for time controls and clock generators and is sometimes even used in switched-mode power supplies. The NE555 – often abbreviated to just the 555 – was first introduced in 1972 by the US semiconductor manufacturer Signetics. Due to its robustness and reliability, it is still used today, with its areas of application ranging from toys to space travel. The NE555 is the world's best-selling integrated circuit.

For the discrete model of the NE555 Timer-IC you will need the following parts:

• 12 pcs. BC557 pnp-transistors
• 12 pcs. BC547 npn-transistors
• 2 pcs. 1N4148 diodes
• 7 pcs. 4.7 kohm resistors
• 2 pcs. 10 kohm resistors
• 1 pcs. 820 ohm resistor
• 1 pcs. 1 kohm resistor
• 1 pcs. 100 kohm resistor
• 1 pcs. 100 ohm resistor
• 1 pcs. 220 ohm resistor
• 1 pcs. 6.8 kohm resistor
• 1 pcs. 3.9 kohm resistor
• 1 pcs. 15x8 cm prototype soldering board (ebay)
• 8 pcs. of aluminum for the IC-legs

The entire discrete circuit is placed on a 15x9 cm prototype board. On the underside you have to connect some parts of the circuit with cables. The IC has a total of 8 legs. I made these out of aluminum.

My discrete NE555 measures around 10x10x4 cm, which corresponds to a volume of 400 cm³. The original NE555 is only 1x1x0.5 cm, which is 800 times smaller compared to my model. Today it is possible to make an even smaller IC (look at the picture). You don't have to forget that this 8pin NE555 has been developed 50 years ago.Today millions of transistors find place on just 1 cm².

With the NE555 you can implement a lot of different timer circuits. The most important are the monostable multivibrator, the bistable multivibrator and the astable multivibrator.

With the monostable multivibrator, the output of the NE555 goes HIGH for an adjustable time after a button is pressed and then automatically drops to LOW.

With the bistable multivibrator, the NE555 changes its state after pressing a button, i.e. changes from LOW to HIGH, then from HIGH to LOW and so on.

With the astable multivibrator, the NE555 automatically changes its state without pressing a button. So it constantly jumps from LOW to HIGH and back again. The times in which it is in the LOW state and HIGH state can be set with an external resistor and an external capacitor. An astable multivibrator is therefore a blinker with an adjustable lighting time and dark time.

I've tested the astable multivibrator and it worked well. With the two potentiometers R1 and R2 in combination wit the capacitor C you can adjust the lighting time and the dark time.

If you are interested in further physics projects visit my homepage or my youtube channel. In this sense stay curious and eureka