We'll cover soldering to large copper pads, like you find on Circuit Playground Express, and soldering to smaller through-hole connections like you'll find on the Feather.

This page will show you the simplest way to connect strips, for smaller low-power projects. If you have more than around 100 pixels, you'll want to connect the power separately, as drawing too much power through the micrcocontroller can cause problems.  See this Powering NeoPixels page for more info.

Do Not Solder to Live Electronics

Be sure your microcontroler is NOT PLUGGED IN while you're soldering to it: not plugged into a battery, not plugged into a wall socket, and definitely not plugged into your computer via the USB port. Only solder to electronics that are completely powered off. Don't get lazy about this, or you may make some very expensive mistakes.

Prepare Your Strip

Follow the steps on the previous few pages to get your strip or ring ready to connect to your controller. Or, if you're using a new strip with wires already attached:

Find the IN end of the strip. Look for little arrows on the strip pointing away from the IN end and toward the OUT end. This is important -- if you solder to the wrong end of the strip it won't work.

If there's a connector, go ahead and cut it off. Also trim off any "extra" power wires, so you're left with just one red, one black, and one white/colored wire. 

These extra wires are there for larger installations where you need to power the strip separately instead of through the microcontroller.

Microcontrollers with Large Copper Pads

Some boards have big, friendly copper pads which make soldering easy. This is not a comprehensive list by any means, but here are some of my favorites:

Step 1: Prepare Wires

Trim your wires so they're more-or-less the same length. If you want to be extra tidy, trim the white wire just a little bit shorter than the other two.

Strip about 1/4" of shielding from each wire.

Step 2: Connect Wires

Twist the stripped wires so they're neat and tidy. Insert each wire through the correct pad or hole on the microcontroller and wrap it around. Connect it firmly, so it wants to stay put on its own. Keep the strands tidy -- you want to avoid any strands touching other pads.

  • Red --> VOUT (or BATT, on some controllers)
  • Black --> GND
  • White --> A1 (or your chosen digital i/o pin from your code)

The labels on the pads may vary based on which microcontroller you're using, but the above is a good rule-of-thumb for most projects.

Step 3: Solder

First, be sure your microcontroller is unplugged and not connected to power. Soldering on live electronics is an open invitation for a visit from the Blue Smoke Monster. He will destroy your board and then laugh while you open the window and try not to cry.

Press your soldering iron to the copper pad right next to where the strands wind through. Leave it there a few seconds so everything gets nice and hot. 

Unspool a bit of solder and touch it to the hot copper pad. It will melt and soak into the stranded wire, creating a good strong electrical connection. It should be shiny and smooth. Use enough solder so the wire gets completely coated and won't come free if you tug on it. 

I like to add enough so the entire hole gets "closed" with solder.

Step 4: Test

If you haven't done so yet, upload some test code to your microcontroller. Here's some test code you can use with the Circuit Playground Express or a Gemma M0 that will run a rainbow along your strip if you attach it to pin A1.

  1. Download the appropriate UF2 file
  2. Plug your microcontroller into your computer with a good USB cable. The lights on the face will turn green. If they don't, click or double-click the tiny "reset" button in the center of the board until they do.
  3. A drive will appear on your computer called CPLAYBOOT (for Circuit Playground) or GEMMABOOT (for Gemma M0). Drag the file you downloaded onto this drive. You're done!

If you're having trouble, head over to the Circuit Playground guide to get things working.

Microcontrollers with Small Through-Hole Pads

There are too many to list, but here are some of my favorites:

Step 1: Prepare Wires

Trim all 3 wires to exactly the same length. Strip about 1/4" of shielding from each wire.

Step 2: Tin Wires

These little stranded wires can break your project if they get "fuzzy" and touch the surrounding holes, which can be maddeningly close by on the smaller boards. 

"Tinning" the wires means adding a bit of solder so all the strands are stuck together. In effect, you're trying to make just a little bit of solid wire, so it will go into the hole easily. The idea is to get all the strands to bond together as one, without making the wire so bulky that it won't fit through the hole.

Use the smallest amount of solder you can, and don't be afraid to trim off any extra solder that balls up at the end of the wire.

Turn on your soldering iron and wait until it's fully heated. If it has a temperature gauge, set it to 750 degrees. Otherwise, just wait about 3-5 minutes so you can strike while the iron is hot.

While you're waiting, get the little sponge in your soldering iron stand wet so you can clean off the tip of your iron. Go ahead and clean it off now, once your iron is hot. It's easier to solder with a clean iron.

Bend your wires up so they're away from your work surface a bit, or use a third hand to hold them steady. Give the ends a twist to be sure all the little wire strands are stuck together.

Heat the exposed wire with your soldering iron, and touch your solder to the wire at the same time. The solder will melt and flow along the wire just a little bit so it gets coated. I like to "stroke" the wire just a bit with the tip of the soldering iron to spread the solder out and make it nice and even.

Do this for all three wires.

If you end up with a ball of solder on the tip of the wire, snip it off with your flush cutters. 

Step 3: Insert Wires into Holes

Which wire goes to which hole will depend on your project's wiring diagram. Here's the wiring that will work with the test code below.

For Feather M4:

  • Red --> BAT (if your project is battery powered) or USB (if you're powering via USB)
  • White --> A1
  • Black --> GND

 

For Trinket M0:

    • Red --> USB (if you're powering via USB) or BATT (if you're using battery power)
    • White --> D1
    • Black --> GND

Step 4: Solder

Make sure your soldering iron is fully heated and the tip is nice and clean.

Press your soldering iron to the copper pad and the wire so it's touching both at the same time. Wait a few seconds until everything gets nice and hot. 

Unspool a bit of solder and touch it to the hot copper pad. It will melt and flow up the wire until you have a nice, shiny blob of solder covering the whole pad and looking a bit like a hershey's kiss.

Snip off any extra wire that's sticking out of the top.

This takes a bit of practice, and there are plenty of exciting ways to get it wrong. Head over to Adafruit's Guide to Excellent Soldering for a whole lot of tips and tricks and troubleshooting. Getting the perfect solder joint is a bit of an art form, and it's something to be very proud of!

Once you get the hang of it, order yourself a soldering sticker. You've earned it!

Step 5: Test

If you haven't done so yet, upload some test code to your microcontroller. Here's some test code you can use with the Trinket M0 or a Feather M4 that will run a rainbow along your strip.

  1. Download the appropriate UF2 file
  2. Plug your microcontroller into your computer with a good USB cable. The lights on the face will turn green. If they don't, click or double-click the tiny "reset" button in the center of the board until they do.
  3. A drive will appear on your computer called TRINKETBOOT (for Trinket M0) or FEATHERBOOT (for Feather M4). Drag the file you downloaded onto this drive. You're done!

If you have a different board, not to worry: all Adafruit's boards have a dedicated guide with test code and pinouts and all kinds of goodies. Just do a search in the Learn System search box to find your board and learn all about how to use it.

This guide was first published on May 13, 2020. It was last updated on May 13, 2020.

This page (Soldering to Microcontrollers) was last updated on Nov 06, 2020.