LEDs Ring Oscillator

This is a simple ring oscillator.

Each of the three transistor circuit work as an inverter and the oscillation is made possible with a feedback loop.

I found a circuit on this website and reduced the number of components

https://hackaday.io/crazycircuits

https://hackaday.io/page/6973-three-transistor-osc...

You can make an oscillator from just two transistors:

https://instructables.com/cheapcomponents:

https://instructables.com/Transistor-Blinking-...

You do not need high power resistors (that you see in my photo) for this circuit. However, you might need high power capacitors.

Parts: general purpose bipolar junction (BJT) NPN or PNP transistors - 5 (you might need spare just in case), 10 kohm resistor - 5, 100 ohm resistors - 5, 1 kohm resistors - 5, 470 uF capacitors - 4, matrix board - 1 (10 cm by 10 cm), insulated wires.

Tools: pliers, wire stripper.

Optional parts: solder, heat sinks, heat transfer paste.

Optional tools: soldering iron.

I drawn the circuit via old PSpice simulation software.

The advantage of this oscillator over a two transistor oscillator is that it allows the sequential switching of each of the three LEDs. You can add additional two LED and two transistors to make a sequential switching of five LEDs.

You can also try swapping positions of capacitors and Rb resistors.

Simulations show that the transistor collector voltage does not increase about 1.5 V. This is due to high transistor current gain.

In practise the transistor current gain could be lower.

I used three 470 uF capacitors. However, you can try 1000 uF capacitor for lower oscillation frequency of 100 uF for high oscillation frequency.

I made the circuit with three AY8139 NPN BJT transistors (TO-39 package).

Testing showed that might circuit was working.

The oscillation might not be oscillating if transistors are not saturating. Initially I tried using 1,000 ohm Rc resistors and the transistors were not saturating. Then I increased the Rc resistors values to 10,000 ohms and my circuit started working.