A Trinket clone using only through-hole components
The goal of this project was to create a Trinket clone using only through-hole components.
- Use only though-hole components. Since there are no through-hole mini-USB B sockets, I opted for a USB A etched right on the board (similar to the Digispark)
- Small footprint. Get it at least as small as the original Trinket.
- Optional fuse. I'm really fond of my USB ports, so for extra peace of mind I added a poly-fuse. I choose a surface-mount ptc fuse, as they tend to be faster than through hole versions. This fuse is optional (as it would break the first goal).
- Different bootloader. I slightly altered the bootloader, to have it go into programming mode, only when the reset button is pressed. So when you power it up, your code will run immediately, instead of after 10 seconds.
- No voltage regulator. The ATtiny85 will work on 2.7-5.5V. If you power your project using batteries, a voltage regulator will just decrease battery file. Just choose a battery with less than 5.5V. Also, I didn't have room for it.
Creating the board
Assembling the board
Since the led has to be at the top (the same side as the copper), I put the leads down, and then back up in the holes next to it. Otherwise you can't have the led flush with the board, as you have to be able to put the soldering iron underneath it.
Here come the brains. I've already flashed my altered bootloader onto it.
Bend over the pins.
I also scraped away the trace between the two pads of the poly-fuse. If you don't add the poly-fuse you should just leave it there.
Here I've also tinned the USB connector. This will make it fit better into the USB socket, and prevent the copper from oxidizing and wearing out.
For a bit of extra bling, I added a few layers of nail varnish. This will prevent accidental short, oxidation and tin-whiskers (just kidding on the last one). I added some extra layers at the top right, where the board might touch the outside/shielding of the USB socket.
Too scale. The board ended up fractionally shorter (29.5mm) than the board of the real Trinket (note that mini-USB sticks out even more). It is however slightly wider. I could just cut away some more of the board, but I'd have to slightly move some components in the layout to match the width of the Trinket. Win some, lose some
Thank you for watching!