Our August 2024 rotating exhibit consists of our Light Emitting Diode (LED) Lab that we use for our STEM events. We are preparing the museum for our OMSI Science Festival 2024 where we will conduct multiple tours on two different days as part of their community outreach.

The lab consists of a TM504 mainframe with a PG501 Pulse Generator, DM501A Digital Multimeter, and a PS503A Power Supply, and a MSO4104-6 Oscilloscope.

The purpose of the lab is to introduce test and measurement equipment and allowing students to actually turn knobs and see things happen. Two tri-color RGB LEDs are used. The first LED is hooked up to the PS503A power supply and DM501A DMM. This experiment is to show the different materials used to make the different color LED die have different threshold voltages where they turn on. Turning the supply voltage slowly allows the student to see the different colors light up and measure the different voltages. This demonstration also shows how combing red, green and blue light produces white light.

The other RGB LED is hooked up to the PG501 pulse generator. The PG501 has the ability to vary the duration of the pulse width. The oscilloscope shows the pulse signal and allows the student to see the correlation between the width and the corresponding brightness of the LED. This is method of dimming is commonly used in cell phones. It makes it easy to see how dimming the backlight can save power and battery life.