IC Orientation

It is vital that integrated circuits are fitted the right way round.

Here's how to find pin 1 on a DIL (Dual In-Line) IC:

A DIL chip always has a physical marker to tell you where pin numbering begins. There are two main things to look for:

The notch — most ICs have a small U-shaped notch cut into one end of the chip. Pin 1 is always at the top-left when you hold the chip with this notch facing towards you.

The dot — some chips also have a small circular indent or dot printed near pin 1, just to be extra clear.

Once you've orientated the chip with the notch at the top (or the dot visible top-left), the pins are numbered like this: starting at the top-left (pin 1), count down the left side, then continue back up the right side. It's a U-shape, going anticlockwise when viewed from above — down the left side, up the right side.

One extra tip for beginners: when a chip is in a socket or soldered onto a board, always double-check the orientation before applying power. Getting it backwards (even briefly) can destroy the chip instantly!