What if we can see the current in a circuit?

Warning: this blog need basic knowledge on basic electronic components.

This circuit below allow the three LED to light up and die out in sequence. It is very impressive to know that a circuit made up of only wires, capacitors and transistors can achieve such an amazing effect.

Original circuit

(quite amazing actually)

However, it is difficult to understand how this circuit and many other similarly amazing circuits work. If there is a way that we can “see” how current moves in the wires, the power of electricity may be known to more people.

The simplest way of detecting a current is to add an LED on the wire. However, LED effects the current a lot. (my LEDs need 3V to breakthrough and the out put current is greatly reduced)

Attempt 1

a LED is added in one of the wire, and the whole circuit stopped working…

(Don’t worry, that blue led is still fine)

The second idea comes from my experience in building logic gate (part of the project is also uploaded on my personal website). In that project, I learnt to use transistors, which can control a strong current with a weak signal(0.7V). However, this still doesn’t work.

Attempt 2.1

The input current and output current are both connected to the base of the transistor. At this moment, the current just don’t effect the transistor.

Attempt 2.2

The input current is connected to the base of the transistor and the output is directed from the emitter. At this moment, the whole circuit breaks down.

The third idea is about relays. Relays are simply electrical switches. The input current is directed to a coil, and the coil will turn the switch on and off.

The problem is that the switch will not turn on unless the input current is more than 5V, and it can’t be reach by simply adding batteries.

Attempt 3.1

The relay can’t move the switch because the voltage is too low. (Though I used a 9V battery for power)

Attempt 3.2

The relay works this time, but the wire it is connected to is not that important to understanding the circuit.

(More leds are used due to the high voltage)

(But this is the only successful attempt)

The last video will show what I want to achieve.

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