Friday, July 29, 2016

DIY ATMEGA8 & ATTINY2313 TQFP SOIC adapters to DIP (THT) from single sided PCB

A few days ago I went to the website of the shop where I usually buy electronic components and they had ATMEGA8A and ATTINY2313 MCUs at 50% off, a very good deal (the equivalent of ~1 US dollar). The catch is that they weren't selling the DIP version of the chips, but the TQFP-32 and SOIC ones.

I wanted to use a few of them in some of my older projects but the PCBs were designed for the DIP packages, so some sort of adapters were needed. After thinking a bit, I wanted them to:

  • Be compact enough to fit the socket of the DIP package
  • Have good mechanical strength so they're not easy to break when using them for prototyping
  • Use a single sided PCB for reduced complexity
  • Be easy to build at home with hobbyist tools

This is what came out:

Atmega8A-AU and ATTINY2313a-SU DIP adapters (front)

Atmega8A-AU and ATTINY2313a-SU DIP adapters (back)

Building took about 10 minutes for each model. Materials you'll need:

  • photosensitive PCB (I used Bungard laminate)
  • 0.6 - 0.7 mm copper wire (like the one found in UTP cables)
  • precision drill with 0.7 - 0.8 mm bits
  • soldering equipment and materials

Steps to build:

- Download and print the PCBs (the PDFs with the layout are available at the end of the article). Use an A4 sheet when printing and don't forget to disable auto-scaling in the PDF viewer.

- Prepare, etch, cut and drill the PCBs using the printed template

Etched PCBs
- Solder the MCU in place, but please be careful at the orientation. The 1st pin is marked with the circle

- Place the PCB with the MCU perpendicular to the one with the DIP template, hold it into place and tack it in 2 - 3 places. Pin no.1 is square and must have the same orientation as pin 1 on the MCU.

AVR soldered and PCBs aligned and tacked together

- Proceed to solder all the other points on this side then insert and solder 1 cm pieces of wire


Adding wires to  the left side of the adapter

- After finishing, prepare some longer pieces of wire for the other side of the PCB. I used a length of 3.5 cm here which was a bit too much but they can always be trimmed later. Bend one of the sides of the wires at a 90 deg. angle.

Preparing wires for the right side of the adapter

- Insert the wires then solder them on both boards

Right side wires added and soldered




- Trim the wires to the desired length

Adapter with trimmed wires

That's it, enjoy your new adapters!

Adapter used in an AVR Doctor circuit


Link for the layout (PDF, A4 size) for both ATMEGA8 / 328P and ATTINY2313:

Solder side:
https://drive.google.com/open?id=0B7qGmYL2UHFNSlVzNk5IUWhXbFE

Silkscreen:
https://drive.google.com/open?id=0B7qGmYL2UHFNNTZJMWpqeklLVlU

Note that the solder side layout is mirrored. When using it make sure you're able to see the text normally through the template.