Recent Blog Entries

Breadboards are great and so are protoboards that are based on breadboard layouts. Well most of the time . They both have problems when you need to use IDC connectors, dual row headers or any other component that has 2 rows of connectors on a 0.1" (2.54mm) grid.



The problem is due to the fact, that you need the connectors on each row to connect to a different terminal strip or protostrip. This cannot be done because each set of terminal strips/protostrips is separated by a 0.3" (7.62mm) gap.

The Prototyping Board, full size, style 2 with IDC support addresses this problem...

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When you were a kid, you may have made a lemon battery for a school science project. These are very simple to make and involves inserting dissimilar metals into a lemon. Typical materials are copper staples and zinc plated nails. This combination usually gives you 0.7V and a few milliamps.



The chemical reaction that happens in a lemon battery is called "Galvanic corrosion" and it also happens when 2 dissimilar metals touch each other. For galvanic corrosion to occur, the following factors must be present:

• There must be two (electrochemically) dissimilar metals present
• There must be a conductive path between the two metals (eg they are touching)
• There must be a path for the charged ions to move between the metals (In the case of the lemon battery, this is the lemon juice)

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Breadboards are invaluable for experimenting with electronic circuits. They allow you to created temporary circuits that can be easy changed. This tutorial explains the basics of how breadboards work and how to use them.

A typical breadboard consists of 100's of holes called tiepoints. These tiepoints are aligned on a 0.1" (2.54mm) grid. The board consists of 2 main sections

• Power Busses
• Prototyping area

The tiepoints in the prototyping area are typically arranged in groups of 5 which are connected together. These are referred to as terminal strips and are shown in the photo below...

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This weekend we released the lastest version of our 28 pin avr board. This version includes 7 improvements which we are pretty excited about.



The changes include:

• Updated external crystal block in ground plane for better isolation
• Updated AVCC block with room for bigger inductors
• 6 pin ISP interface in addition to the existing 10 pin interface
• 300mil (7.63mm) gap between I/O port and 5 hole protostrips. A resistor, piece of wire, dip switch
  or other component of choice may be used to bridge this gap
• Power rails are double sided to allow for greater current
• Better pin layout for reset switch
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Ever wanted to drive you etch-a-sketch from your computer, well one guy did and this is how he did it!



The concept is pretty straight forward. The interface to the notebook is via a parallel port, there are a pair of stepper motors that turn the knobs on the etch-a-sketch, and an ATMEGA8 sits in the middle.

One of the design challenges was that the stepper motors were rated at 24V and also drew a fair bit of current. A pair of uln2803 darlinton arrays were used with 2 channels used for each step. Each channel on the array can handle up to 500ma, so this provided adequate current for the motors.

To find out more, have a look at http://www.unfocusedbrain.com/site/2009/03/03/the-cnc-magic-screen-machine/.

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