LED Bar Graph

This article shows a simple bar graph display that does not need any semiconductors, only the LED lights.

I also implemented a basic transistor bright LED driver in the same box.

The video shows how well this circuit is working.

Parts: 10 LEDs, 1 kohm resistors - 10, Other resistors - shown in the circuit, metal wire or insulated wire, matrix board/piece of cardboard/piece of plastic, power source (at least 4.5 V and not more than 9 V), battery harness.

Tools: pliers, scissors, variable voltage power source.

Optional tools: soldering iron, wire stripper, screwdriver.

Optional parts: solder, bright LED, a general-purpose transistor - 2, encasement, bolts, nuts, washers, and metal connectors.

I have drawn the circuit in the old PSpice simulation software.

The maximum LED current is about 8 mA. If you reduce the supply voltage to 4.5 V then the maximum LED current will fall to about 4 mA.

I used typical diodes instead of LEDs diode because the old software does not have an LED component.

The LEDs should not be supplied with a current that is more than 10 mA.

Each of the seven LED channels can be converter to Thévenin's equivalent. Thus you can calculate the maximum current by clicking on this link: https://en.wikipedia.org/wiki/Th%C3%A9venin%27s_th...

I did not use a soldering iron. I used pliers to connect the wires.

I implement the transistor inverter/LED driver with two BC558 BJT PNP transistors, two 1.2 kohm resistors, and a bright LED.

Testing shows that the bright LED is a good light source.

You can see this circuit working on the video.