How to Make Circuits in the Fab Lab

Making a circuit requires several mini-projects:

Design and Architecture

Decide what function your circuit board should have

A good approach is to write down in words how the circuit board should work.

• download a cad file from the hello-world circuits section on the http://fab.cba.mit.edu/about/fab/ or from hello world electronics
• Look for open hardware solutions on the internet.
• Or design custom circuit

Create the schematic and board layout in a CAD program

Use e.g. Eagle or Cad.py, ,or Gimp (drawing tool), Inkscape or Open Office or draw it with black pen and scan and trace. The gap should be the right size and shape.

• Eagle

Physical Fabrication

Machine the board

Physically milling or cutting out the board which connects components

• Making circuit boards on Modela
• Making circuit boards on Camm with e.g. copper foil.
• Making circuit boards on Epilog Laser

"Stuffing": Solder components on to the board

Solder the components to the board. If you want to where the components should be you could look at the file design, in .cad file or you can check out

• Soldering -> Gisli
• Good Vs. Bad Soldering
• Circuit descriptons. pdf
• Scotts new Hello World Circuits description

Microcontroller Programming

Make a programming cable

There are several different types of cables used to program the AVR microprocessor. The cables are different based on the number of wires used, the types of connectors on either end, and the program used on the computer for downloading hex code to the processor.

• DASA programming cable uses the serial port on the computer and the program avrdude. The microcontroller end may use an MTA connector, 6-pin ISP connector, or programming clip. Consult this guide for making cables with MTA connectors.
• DAPA or BSD programming cable uses the parallel port on the computer and the program avrdude or uisp. The microcontroller end may use a MTA connector, 6-pin ISP connector, or programming clip.

Write the Program

Write the program (in e.g. assembler or C) , compile the program so that the microcontroller will understand it -> Jan

Programming the microcontroller

If you are using the Fab Labs, AVR microcontrollers

• Use ICP (In Circuit Programmer), sometimes often called ISP (In System Programmer)
• AVRDUDE
• Few Linux commands used to program AT Tiny 45

-> Jan

Testing and Troubleshooting

Test the microcontroller

Plug the microcontroller in.

• Is the power on?

Troubleshooting

If your board is not working, follow the step to troubleshoot it:

Check	Problem	Possible solution
Battery voltage	Voltage too low	Replace the battery
Microcontroller voltage terminals	No voltage or too low (it should be around 3,3 V to 5 V for the hello boards)	Follow the track and check every component voltage (capacitor, voltage regulator) Check the solder there is no electrical continuity If the solder is ok, replace the component (Learn here how to un-solder properly)
Solder	Doesn't do what I wanted	Check every single solder (Learn here how to solder properly) Check the voltage
Code	Doesn't do what I wanted	Take a breath and review your code

If you cannot download your code to the microcontroller, follow the step to troubleshoot it:

Check	Problem	Possible solution
If the cable is done right	Software avrdude gives error: avrdude:AVR device not responding; avrdude: initialization failed, rc=-1 Double check connections and try again, or use -F to override this check.	Follow the Making serial cables tutorial to build a cable Check for electrical continuity at the cables end
Permissions on accessing port 0	Error running avrdude: avrdude: can't open device "/dev/parport0": Permission denied avrdude: failed to open parallel port "/dev/parport0"	Type the following to see the permissions on the parallel port 0 ls -l /dev/parport0 Type the following to change permissions to users sudo chmod 0766 /dev/parport0 Type the following to check if the permissions were changed ls -l /dev/parport0

External Links

• [http://sound.westhost.com/troubleshooting.htm]
• [http://www.morsex.com/building/atoz4.htm]