The 74HC138; 74HCT138 decodes three binary weighted address inputs (A0, A1 and A2) to eight mutually exclusive outputs (Y0 to Y7). The device features three enable inputs (E1, E2 and E3). Every output will be HIGH unless E1 and E2 are LOW and E3 is HIGH. This multiple enable function allows easy parallel expansion to a 1-of-32 (5 to 32 lines) decoder with just four '138 ICs and one inverter. The '138 can be used as an eight output demultiplexer by using one of the active LOW enable inputs as the data input and the remaining enable inputs as strobes. Inputs include clamp diodes. This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC.

Main Content

8x8x8 RGB LED Cube

“An animated cube made with 512 RGB LEDs driven by an ATmega328.”


“I have previously done a project about “INTERACTIVE RGB LED TABLE” with A2 size, 16x16 RGB LED matrix on foam sheets. I gifted it to my friend. Today, I will share how to implement this project by designing an INTERACTIVE …

Multi-Effects Internet Clock

“I have six red matrix LEDs in my warehouse, it seemed I bought them when I was a student about 15 years ago. It’s surprising that theyre still in good condition. Today I’d like to share how to …

Led Matrix Touch Control

“This time Ill share how to integrate touch control into the bi-colors led matrix 16x32. It can be used to control indoor devices via led panel or carry out some interactive effects by touch action. It may sound strange but …