With the help of LEDs you can produce optoelectronic display units which can be used to show numbers or other characters. The anode of each LED on the display presented containing seven segments is connected to a common positive potential (that is, connected in parallel by segment). The desired LED can be switched on by connecting the cathode of the individual LEDs to the negative potential. Each segment on the enclosed picture consists of at least two LEDs, therefore a power supply source of at least 4.5 volts is needed. 1. Switch the LEDs’ cathode to the negative potential so that the LEDs indicated the digits from 0 to 9! 2. Display for instance the letter L by using the LEDs!

Implements required for the experiment

– 14 LEDs, or prism-shaped LEDs
– Hard paper
– 4.5 V power supply source