The GPIO LED Board for Raspberry Pi

DIY Electronics Project


Designer: jschrempp
Description: The GPIO LED board for Raspberry Pi
Assembly Time: 1 hours
Skill Level: Intermediate

The Raspberry Pi is an excellent experimenter's Linux platform. Not only do you get a full Linux system, but it has a number of pin outs that can sense and control other devices.

The RPi board has a standard 26-pin connector called the GPIO. All the pins needed to run LEDs are in this connector, but how do you get those pins to your LEDs? The GPIO LED board solves that problem.

Once assembled you can connect the GPIO LED board to your Raspberry Pi and start using software to turn the LEDs on and off. A good place to start is the WebIOPi application that is available for free in the Raspberry Pi Store application on your RPi desktop.

Required tools and components:

Qty.
Description Manufacturer Part No.
10
Resistor, CF, 2.2KΩ, 1/2 Watt CF1/2W222JRC
10
LED, 3MM, T1, Green, DIFF LTL-4231
1
Header, 26 Positions, Straight 7000-2X13SG
1
PCB ---

Sample Code
Soldering iron and solder
Wire Clippers
Raspberry Pi GPIO 2x13 cable

Mounting the Connector

Place the circuit board on the table in front of you with the square outline facing up as shown. Place the short end of all 26 header pins into the circuit board. Use a small piece of tape to hold the pins in place and solder the header pins.

2x13 Pin Header2 x 13 Pin Header
Header TapedHeader Taped

Mounting the Resistors

Turn the board over so that the connector is on the bottom. The resistors will be placed on the OPPOSITE side of the board from the connector. Locate the holes for the 8 resistors as shown in the photo. Bend the wires for the resistors, place them in the holes and solder them in place.

Resistor MountingResistor Mounting

Mounting the LEDs

The LEDs will go on the circuit board on the SAME side as the resistors. Locate the 8 pairs of holes. Note that each LED has two leads, one of them slightly longer than the other (the longer lead is the (+) lead). The longer (+) lead MUST go in the hole that is closest to the resistor for each LED position.

LED MountingLED Mounting

If using your GPIO LED board with the Shrimpware Bread Box, mount each LED slightly above the PCB.

The photo on the left shows the LED inserted into the board. The leads are bent about 1/8th inch below the board. The photo on the right shows the LED pushed up into the position where it is ready to be soldered.

Wire Tie TipWire Tie Tip


Tip: Place a small plastic wire tie under each LED as shown in the photo to the right. This places all LEDs at the same distance above the PCB. Once you have soldered the LEDs in place remove the wire tie.

A Raspberry Pi with WebIOPi installed

Before connecting the GPIO LED board to your Raspberry Pi, you need to carefully inspect it. Look at each solder pad and make sure that there is no solder crossing between pads. This is particularly important at the 26-pin connector. Any solder that bridges two pins can permanently damage your Raspberry Pi.

If you have an ohm meter, you can test the resistance between the ground pin and the 5VDC pin; there should be infinite resistance. There should also be infinite resistance between the ground pin and the 3.3VDC pin. If either of these tests fail do not connect you GPIO LED board to you Raspberry Pi.

Once you are sure that the GPIO LED board is correctly assembled, connect the ribbon cable to the 26-pin connector. Connect the cable so that the white stripe is near the LEDs and resistors.

Ribbon Cable ConnectionRibbon Cable Connection

Bend the cable as shown in the photo above. The other end of the cable attaches to the 26-pin GPIO connector on the Raspberry Pi. The white stripe goes towards the RPi's edge.

Open a remote desktop to your RPi and access the Raspberry Pi store application to download the free WebIOPi application. Once it is installed go to the "My Software" tab in the RPi store and double-click the WebIOPi application to bring up the WebIOPi control page.

Your LEDs are connected to GPIO number 17, 18, 21, 22, 23, 24 and 25. (Note that in the WebIOPi screen shot below pin 13 is incorrectly labeled GPIO 27. It should be GPIO 21.) On the WebIOPi page click to make the pins OUT. Then click the square of each pin to watch the corresponding LED light up.

PIN DiagramPIN Diagram