Tuesday, November 13, 2012

Handmade/Homemade Board: "My Arduino III"

My Arduino III by Carlos RodriguesI love homemade boards, and this layout is by Carlos Rodrigues is lovely!  From Flickr:
Construir o meu próprio Arduino, fase 3: alguns upgrades.

Tem agora melhor protecção contra ruídos na alimentação, reset automático ao iniciar um upload, protecção contra excesso de corrente no USB, e o bootloader do Arduino Uno.
Translated by Google:
Build my own Arduino, phase 3: a few upgrades.

You now have better protection against noise on power, automatic reset to start an upload, protection against excess current in USB bootloader and Arduino Uno.


Friday, November 9, 2012

New Arduino Micro

Adafruit did a lovely job with the Arduino team on the new official Arduino Micro. Everything is tiny, with a smaller ATmega32u4 and parts on the top and bottom, some the smallest components available-- seriously micro! It's available now for $25.

Tuesday, November 6, 2012

Pantry Light Demo

The pantry light is installed and working perfectly: I'll post code and circuit details eventually, not much to it though.

Thursday, November 1, 2012

555-Based Dimmer 3D Circuit

I built this 3D, freeform circuit as a test project. I've seen a few lately and love the way they look, and after making this circuit, I'm excited about this method as an alternative to point-to-point soldering or etching for small, one-off boards.

It's a dimmer circuit: a 555-timer-based PWM generator driving a high power MOSFET.  I kept it simple and focused on a method, not on making anything particularly fancy.

Here's a video walk-through of the circuit:

I edited a schematic for a board I'd built earlier, adding a scrounged 10k audio potentiometer with switch.  The parts list was short:
  • 10k potentiometer with switch,
  • 2 2-pin screw terminals (input and output),
  • NE555 8-pin chip,
  • fat npn MOSFET,
  • 2 1N4148 diodes,
  • 2 capacitors: .1uF and 1uF,
  • 330 ohm resistor
The first step was the Eagle board layout.  With air-wires I moved things around for a while to get things close, and routed and rerouted a few times before setting some guidelines:
  • Put the major components where you want them first.
  • Pack the rest of the components in paying attention to keeping traces short.
  • Small 2-lead components can fit later, with one lead overlapping its signal, the other reached by a branch made from its lead.
  • Lay out a few long traces that hit the most pins and cover the most ground first.  Try to get those traces in a straight line or aligned in an L- or S- or U- arrangement, more or less.
  • Avoid branching, unless the branch can be a component's lead.
  • Small kinks and zig-zags are OK and may be built with straighter wire segments later, with pins bent to get where they need to be. 
  • Don't think much about top/bottom layering and about crossing lines.  There will be room to cross a wire here or there.  Try not to cross, but you can worry about top and bottom later.
Then on to building, which breezed by.  Pre-bent wires made it a straightforward, by-numbers sort of thing, and I used the components' leads instead where I could,  reducing the number of parts.  Building notes:
  • Print out a sheet to see the circuit different ways, to use as a pattern.  Run the same sheet through the printer, taking advantage of the print options:
    • Aligned top center, scale 2 or 3 (what will fit), with all layers drawn.
    • Aligned lower left, scale 1, with all layers,
    • Aligned lower right, scale 1, just the traces.
    • Note: also print scale 1 mirrored versions too, of all layers and traces only, to see things from the bottom, which is how things are soldered.
  • In the trace-only print-out, number the longest traces to make wires for them.
  • Strip a length of stripped solid-core wire for each long trace.  Bend them to shape with pliers, clipping to length, using the trace-only print as the pattern.
    • Small kinks in the pattern don't generally need to be bent-- wires and pins will bend during soldering.
  • Clip leads after soldering, unless it has to butt up as a T.  It's easy to clip after soldering, and wires can shift during soldering.
I kept it simple and methodical so I could scale it up to bigger circuits.  I have to say that the result surprised me in how quickly and easily the board came together.

I'm looking forward to using this on a few other cicruits, maybe a PIC-based USB-serial converter, or a multichannel MOSFET-based switcher or SSR or... good stuff from this :) Then there's the question of how to mount this, or cast it in some material.

3D Circuit Construction

Rupert Hirst's amazing resin-encased headphone amplifier is a work of art and shows a novel (to me) way of building a circuit without any mounting board. His buildlog shares many great details, especially about the casting process.

Mats Engstrom has shown a few 3D circuits lately too: a Little Wire programmer circuit built boardless with SMD components (at left) and encased in resin, and a Freeformed Nixie Tube clock with a beautiful radial design inside a box-like frame.

Kimio Kosaka files his incredible "Arduino Skeleton" board under "O'baka Project" which he says: "means a stupid project. This project is to make things which is not art and which is not usable. Now, I am making Arduino skeleton by using steel wires." Hmm, they look like usable art to me! Maybe a mis-translation. He lists instructions:
    How to make.
  1. Design single side PCB by EAGLE-CAD. (Base circuit is Metaboard)
  2. Print out this PCB pattern.
  3. Trace this PCB pattern by steel wire. (0.46mm in diameter)
  4. Soldering

    I used a flux of the strong acidity for the steel wire soldering.

His "One Chip Arduino" has no board either, stressing economy.

I find more examples the more I look, like this 3D alarm clock, video about using a CD as a circuit board, and Make: uses the tag "freeform" for freeform circuit layouts on its blog.

These inspired me to make one of my own, which turned out to be a faster, easier, cleaner way to make a simple 1-off circuit than home etching or point-to-point soldering, if the process is refined.