The ATtiny85 chip is a simple $2 way to get into Arduino.
It's the basis of low-cost microcontrollers like the Digispark, the Picoduino, the Trinket, and for e-textiles, the Gemma, and the LilyTiny.
These off-the-shelf boards are brilliantly designed and great for one-offs. If, however, you need a bunch (or you're feeling crafty), you can make your own wearable board.
Stripboard (aka veroboard)
Chip - ATTiny85. Learn more about it here.
Chip socket - 8 pin
Dremel with cutting wheel (or a box cutter)
Soldering workstation (soldering iron, safety goggles, fume extractor, tip cleaner, etc.)
Programming shield for ATTiny85
Chip extractor tool
Step 1: Cut the stripboard
Clamp the board so you can cut it.
Using the dremel, cut the board to size: for an 8 pin chip, I cut a board 4 rows x 10 holes.
(Don't breathe the dust!)
Next, on the copper side, lightly cut a groove down the middle through the copper layer only so your 4 rows are now 2 columns.
Use a multimeter to make sure the left columns are completely separate from the right.
Note: You could do this with a boxer cutter instead of a dremel. Score the board by running the box cutter along a ruler clamped in place. Snap it along the score. Cutting this way is less accurate so make the board larger to compensate. The box cutter will also work on the copper traces.
Step 2: Bend your leads
Gently bend the leads of your chip socket out on each side, so they're parallel to the socket.
Try bending against a flat surface like a table top.
(You could also skip the chip socket and solder your chip to the board this way. Make sure you program your chip and sew on your board before you solder!)
Step 3: Solder the leads
Lay your chip socket (or chip) on top of the board and clamp it in place.
Heat up each lead/copper pad with the wet tip of your soldering iron. Feed in your solder. Tin the rest of the copper pad as well.
Next, solder whatever connections you'll be using.
***If you're working with conductive thread, see my instructable on soldering conductive thread. ***
Note: you could just poke the leads through the holes without bending them, the way stripboard is designed to be used. I do it this way to avoid leads poking out the back and conductive surfaces that could short on wires underneath. (Also, I like the way it looks.)
Step 4: Connect your board
Sew the board to your fabric, like you'd sew a button. I used a beading needle and "invisible" thread.
Solder (or sew) the lines from the board to wherever they need to go.
Finally, program your chip, and gently press it in to the chip socket.
(Congratulate yourself on being awesome.)
I used my board to make a collar with a heartbeat, on a knitted circuit.
*If you need to re-program, you can remove the chip with the chip extractor. It's possible to do this with your fingers or a pair of mini screwdrivers, but be very careful not to bend the legs as you pull it out-- easier said than done. Practice on a throw-away chip before you do.