The other useful web page I found was a post in the Raspberry Pi Forums, where Bertwert had published a Python script to turn one of these displays into a clock. It’s also easy to detach from the Pi without undoing and messing up all the wiring. I wired it directly to the Pi the first time, but when I wanted to re-order the wiring, I found it much easier to use the RasPiO ® Breakout. For a 12-wire project, this is extremely useful. This means you can do all the wiring “off-Pi” and then attach the project all at once. I used one of my RasPiO ® Breakout boards and a 170 point mini-breadboard to wire up the 7-segment display. Here are the connections you need to make… But if you connect these segments directly to a 3V3 source off-Pi without current-limiting resistors, you will damage or kill the leds in the segments (yes of course I tried it). In reality, we’re switching fast, so each segment should only be ON for a short time. I’ve opted for 100 Ohm, which gives the LEDs a little protection. We also need some current-limiting resistors. We need some Python code to handle this for us, and we’ll do it using 12 of the Pi’s GPIO pins (4 to switch the digits and 8 to switch the segments). Using the same circuitry to control more than one ‘thing’ is called multiplexing.

The way that you get each digit displaying something different is to switch them on and off again, in turn, faster than the eye can observe. But How Can We Use That? It’s Impossible? So if we had 12, 9, 8 & 6 all connected to GND, and 7 & 4 HIGH, all four digits would display the number 1. If you connect pin 12 to GND, the first digit will activate (9 = second, 8 = third, 6 = fourth).īringing each of the other 8 pins HIGH activates a specific segment on all currently active digits. Common cathode 4-digit 7-seg pinouts How Does It Work?

Html font style 7 segment display