The Level Shifter Guide

FOR: RASPBERRY PI + WS2812B LEDs

COMPONENT: 74AHCT125
STATUS: APPROVED

1. POWER SUPPLY (5V)

V+ (5V)

V- (GND)

2. RASPBERRY PI

USB PWR

GPIO 18 (Pin 12)

GND (Pin 6)

3. LEVEL SHIFTER (74AHCT125)

TOP VIEW (Notch Up)

1: 1OE (GND)

2: 1A (IN)

3: 1Y (OUT)

4: NC

5: NC

6: NC

7: GND

14: VCC (5V)

4. LED STRIP

5V (RED)

DIN (DATA)

GND (WHT)

1 Power the Chip

The chip needs its own power to amplify the signal.

Locate the Notch (dimple) on the top of the chip. Orient it UP. Connect Pin 14 (Top Right) to your 5V Power Supply (Red Wire). Connect Pin 7 (Bottom Left) to Ground/GND (Black Wire).

2 Enable the Channel

The chip has an "On/Off" switch called Output Enable (OE). It is "Active Low", meaning you connect it to Ground to turn it ON.

CRITICAL STEP: Connect Pin 1 (Top Left) to Ground/GND. If you forget this, the lights will stay dark!

3 Route the Data

We are going to enter the chip with weak 3.3V signal and exit with strong 5V signal.

INPUT: Connect Raspberry Pi GPIO 18 (Physical Pin 12) to Chip Pin 2 (1A). OUTPUT: Connect Chip Pin 3 (1Y) to the DIN / Data In on your LED Strip. (Optional) Place a 470Ω resistor between Pin 3 and the LED strip to protect the first pixel.

4 Common Ground Check

Ensure the entire system shares a "floor" voltage.

Verify PSU GND is connected to Pi GND. Verify Pi GND is connected to Chip Pin 7. Verify Chip Pin 7 is connected to LED Strip GND.

✅ Why are we doing this?
The Pi outputs 3.3V. The LEDs consider anything below 3.5V as "undefined" or "low". The Level Shifter takes the Pi's 3.3V "1" and boosts it to a 5V "1", ensuring perfect glitch-free colors.