The Fab Academy Assignment make and program a board

The Project: Fab ISB

The FabISB was designed by David Mellis. It is an in-system programmer for AVR microcontrollers. Mellis designed it so that it could be produced in a Fab. It’s based on the USBtiny and V-USB firmwares, allowing the ATtiny44 to communicate over the USB connection. It can be programmed with avrdude. See Mellis’s site for more details.

Skills Learned

This was my first board that I put together and programmed at Fab Academy

I learned how to:

• mill a board
• stuff a board
• program a board
• troubleshoot a board

I had a alot of trouble initially with this board and I made at least 6 of these at various stages of completion before I got the final one working. Some of the issues were due to my inexperience and need of practice with soldering and troubleshooting, but I discovered later that many of the problems were also due to the programmer I was using (see below).

Tools Used

• ATMEL Mini AVR ATMEGA STK500 USB Programmer ISP (initially)
  • I had a lot of trouble with this programmer. I could not get it to green light on most of my boards - and when I did get a green light, it was unreliable. It would often go green - then yellow - then red. I would unplug it and then plug it back in and get flashing yellow or green.
  • I also wanted my own programmer to work with at home (the Ateml Mini belonged to the lab), so I purchased the very inexpensive USBtinyISP kit. This turned out to be a great solution. I occasionally have an issue with it heating up the boards a bit, but it doesn’t give me flaky results like the Atmel mini. Without the USBtinyISP, I would not have been able to complete any of the electronics / board related assignments with fabbed boards.

• USBtinyISP AVR Programmer Kit
  • I found this programmer much easier to use than the Atmel Mini.
  • available from Adafruit Industries
  • post on putting it together here (link to post)

I built Shawn's modified FTDI version of the step response board and got it working, I'll edit this entry to add pictures later.

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I'll admit it: I've been having trouble with traces ripping up after repeated use of the surface mount pin headers we've been using in the lab. Here is a solution: a development board for the Attiny45 that is easy to use with a breadboard or to incorporate into a project with through-hole wire connections. It also has a sturdy six pin header for an FTDI USB to TTL cable. The Eagle schematic and board files are linked below:

Schematic

Board

I demonstrate soldering components onto a step response circuit board that was milled on a Modela CNC router. My technique is informed by my soldering experience in silversmithing.

At first, the camera wouldn't focus on close- up shots. Brandon had the great idea of placing a magnifying lens in front of the camera. This setup worked wonderfully!

Today I milled out my first PCB on the Modela. Technically it is not a “printed circuit board”, but machined out of copper-clad PCB stock.

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Fab Academy Assignment

The assignment is to design a circuit board, mill it, and program it in assembly language. This post documents Part 1 of this process which entails:

• Designing the board (For this board I used the already created Fab ISB board file - I plan to design a board for a later project).
• Machining the board

Part 2 will document the process of putting the components into the board. Each student had to become acquainted with the following work flow:

• Stuffing components
• Programming

The first step in making a board is to create a tool path to send to the machine:

To Mill the Board:

• Import a PNG image into cad.py.
• Create the tool path in cad.py
• Send to the Modella

To Cut through the Board:

• Import the border PNG image into cad.py
• Create the tool path in cad.py
• Send to the Modella

Published in the MAKE Blog.

Our assignment this time around was to design a circuit board, mill it, and program it in Assembly language. Each student had to become acquainted with the following work flow:

• Designing the board
  
• Machining
  
• Stuffing components
  
• Programming
  

Makeda Stephenson in the Providence Fab Lab

In a Fab Lab, circuit boards are either milled from copper-clad PCB stock or cut on a vinyl cutter from copper tape with conductive adhesive. We try to avoid the etching process in order to limit the used chemistry we have to deal with. Whether etching or cutting, the first step is to choose one of the options for creating a tool path to send to the machine:

1. Draw the circuit as a black and white PNG image and bring it into cad.py for tracing.

2. Draw the circuit using Eagle, a free PCB drafting tool, and export Gerber files, a standard format for PCBs. Gerber files can be converted into PNGs using gerbv or the online tool from circuitpeople.com. Bring the PNGs into cad.py for tracing.

3. Draw the circuit in Eagle and use Eagle's CAM processor to generate mill and drill files that can be sent directly to the machine. This process was described by Marc Boon in a workshop at the Amsterdam Fab Lab in 2008.