Here is a quick tip for soldering up the Raspberry Pi Zero GPIO connector.
The Raspberry Pi Zero and Zero W are amazing little microcomputers that can be obtained with very little cash outlay. Starting at just five dollars these little wonders sport HDMI outputs for full HD video, USB OTG (On The Go) connectors and even a port for the Raspberry Pi Camera. But one thing is missing – the Raspberry Pi GPIO connector for expanding the boards with Raspberry Pi HATs.
To be fair they had to cut costs somewhere and in actual fact the GPIO connection is there, it just lacks header pins. In many cases you won’t miss it, your project may not need any I/O pins or it might just use a couple that you can solder wires to and use as they are. But if you want to install a HAT you’ll need to solder in a 40-pin GPIO connector.
The GPIO Connector
All Raspberry Pi microcomputers have been equipped with a General Purpose Input/Output or GPIO connector of some sort. The early models used a 26-pin connector, starting with the Raspberry Pi 2 this was expanded to 40 pins. Both the Zero and Zero W use this 40-pin standard.
The GPIO connector allows you to expand your Pi by attaching additional circuit boards known as HAT’s (Hardware At Top). You can get HAT’s that have fancy displays, that drive motors or that read sensors, and you can make your own HAT’s as well. You can also connect a “T-Cobbler” to your HAT, this is a device that uses a cable and a T-shaped circuit board to bring out the connections from your Raspberry Pi to a solderless breadboard so you can run your own experiments.
A diagram of the pinouts of the 40-pin GPIO connector is shown here:
One thing to keep in mind when experimenting with Raspberry Pi inputs and outputs is that they use a 3.3 volt logic levels, unlike most (but not all) Arduino’s that use 5 volts. Bear that in mind if you plan to connect external devices to your Pi.
Get the bits Together First
So let’s mate a Raspberry Pi Zero with a 40-pin GPIO connector.
First of course you’ll need a Pi Zero or Zero W, as the demand for these little gems is high they can sometimes be a bit difficult to obtain. However since you are reading this I will assume you either have one or that one is on order now.
Next you’ll need the header, a 40-pin male 2-row header to be specific. If you can’t find one you can take a 40-pin male single-row header (which are very easy to find) and cut it into two pieces.
Naturally you’ll also need a decent soldering iron or soldering station and some solder, but I’m sure you know that already! Make sure your iron has a small tip, if you do any electronics work you probably have that covered.
If this is your first attempt at soldering I suggest you practice a bit first on some scrap printed circuit boards to get a feel for it, rather than risk damaging your little Pi – even though it costs less than you probably spent last time you went out for lunch.
Now for the fun part!
The subtitle is a bit of a misnomer, there isn’t really anything tricky about soldering a 40-pin header to your Pi Zero. The ”tricky” part is getting everything held together so that you can make a good connection.
First let me tell you how I don’t do it. You’ll find several instructions on YouTube that instruct you to use a solderless breadboard to hold the header in place. This actually works very well, however it isn’t the best thing to do to your breadboard. The pins on the header are a bit thicker than the wires and test leads that you use with your breadboard, so when you mount them on your breadboard you’ll expand the tiny connections a bit. After a few times of this kind of treatment those connections will start to make poor connections with jumper wires or the pins of integrated circuits. Poor connections on a breadboard are no fun!
Of course if you’re willing to sacrifice a breadboard just for soldering headers (Pi Zero and other headers) then by all means go for it, breadboards do make a nice base to hold everything together. But if you value your breadboards then consider my method.
Perfboards are those circuit boards that are full of little holes and that are used for prototyping circuits. No experimenter should be without a good supply of them.
There are differences in the quality of perfboards. Good quality perfboards have connections on both sides and the connections are plated through, just like on a professional PCB. Make sure you have a few of these around for your next electronic project, but don’t use them for my “Header Trick”!
What you actually want are cheap, single sided boards. Ones that are not plated through. The lowest quality ones you can find. Seriously!
You see these boards are not really worthy of your fine electronics designs but they are wonderful at holding in header pins. Just shove them into the board and you’ll see that they are a tight fit. Which makes them perfect for holding a GPIO connector.
If by chance your cheap perfboard doesn’t hold the pins perfectly just use a second one beneath it, that should do the trick.
So place your 40-pin header (or two 20-pin single headers) into a perfboard and mount the Raspberry Pi Zero onto it, upside down as shown below. Then just put the whole assembly into a circuit board holder or “third hand”. And get ready to solder!
Outer Pins First
When you are soldering the header to the Pi Zero start with one of the corner pins. Make a nice connection, remember to heat the header pin and to let it melt the solder (don’t just melt the solder directly with the iron and expect it to stick) . Don’t linger on it too long as you don’t want to damage the board, although the Pi Zero PCB is of excellent quality and is pretty tough.
After you do the first pin move over to the pin on the opposite diagonal corner and solder it. Put a bit of pressure on the Pi circuit board so that you are sure the header is mounted with its pins inserted as far as they can go.
Once you have the two diagonal corner pins soldered you can solder up the rest in any order that feels comfortable to you. Take your time and inspect each connection to be sure you don’t have any solder bridges.
After you solder the Pi Zero GPIO Connector to the board you’ll inevitably have some flux residue left over. If it doesn’t bother you it can be left there, but if you want it to look professional use a bit of Flux Remover (available at your local electronics store, assuming you have a local electronics store) to clean it up. A cheap (unused) toothbrush is really good for scrubbing the connection with flux remover. Be careful not to splash any of it into your eyes.
Once you have cleaned up your connection and inspected it again for solder bridges you’re done! Your Raspberry Pi Zero now has a GPIO connector, ready to accept any compatible HAT.
Now all that’s left to do is to figure out what you are going to use it for. As there are at least a few thousand applications I’ll have to leave that up to you!
And hang on to those cheap perfboards, they’ll come in handy the next time you need to solder headers to any circuit board.
Raspberry Pi Official Site – The official website of the Raspberry Pi Foundation
Raspberry PI GPIO – A cool utility that helps you understand the GPIO connections
Understanding the Pi GPIO – A detailed explanation from the Raspberry Pi Foundation