2-Layer Circuit Boards Using Laser Cutter / Chemical Etching

I've kind of been obsessed with trying to make circuit boards on my laser cutter since I got it. Other people had already done this by using spray paint as resist - then laser-etching the paint off non-trace portions of the board. This process still requires chemical etching - which I've been trying to avoid.

I had some success several months ago - making crude PCBs by laser cutting thin steel - but those boards aren't good enough for surface mount components or anything complicated.

So - if I can't make good boards without chemical etching - I figured maybe I could use chemicals in conjunction with the laser cutter to make some decent 2-layer boards.

After a few failures - I came up with the process documented in the video. It works pretty well! I suspect if streamlined a bit - you could go from Eagle to working board in under 90 minutes.

My first project is a demo board for the ATtiny43u - a nifty little microcontroller that uses a voltage booster to run on as little as 0.7 volts. The booster can even power small external devices requiring a higher voltage - like an LED.

Resources:
Eagle files for ATTiny43u Board
Etching with Copper Chloride in Aqueous Hydrochloric Acid Solution
Atmel ATtiny43u
Youritronics - Double layer pcb home made vias

Money Shredding Alarm Clock

A while back I fumbled into Acid Cow's idea for a Money Shredding Alarm Clock.

I figured turning the concept into reality shouldn't be too hard.

All I needed was a few main parts:

SparkFun's ClocKit
A USB Powered Paper Shredder
TIP120 Darlington Transistor
(I also used an Atmel AVR programmer I already had)

Surprisingly the ClocKit managed to use every single pin on the Atmega328 it runs on - leaving me without an obvious control pin for the shredder.

I noticed that two I/O pins were being used for the alarm buzzer - which seemed unnecessary. I reconnected one of the buzzer pins to ground - and the buzzer continued to work fine - freeing up the needed pin to connect the TIP120 to.

About 30 seconds worth of code changes - and my alarm clock was working!

I swapped in a larger 5v / 1 amp power supply after seeing a "reboot" when the shredder fired up (probably voltage sag). Seemed to address the issue.

Tip - check the voltage on wallwarts with a multimeter before connecting them to anything sensitive like a microcontroller. A cheap 5v wallwart might put out closer to 8v unloaded.

Laser Cut Circuit Boards

I've had my laser cutter (Full Spectrum 40-watt CO2) for about 1.5 years - and over that time have spent a good amount of time trying to make circuit boards on it.  To be clear - I wanted to cut circuit boards.  Others have used their lasers to remove resist - to ultimately chemically etch boards.  

The barrier was cutting the metal.  I tried various tricks to cut copper - with little luck - even with unimaginably thin "copper leaf".

Then an employee of a local commercial hackerspace mentioned he'd cut .001" stainless steel shim. Stainless isn't solderable - but it made me wonder if mild steel could also be cut (which is solderable).  Turns out you can!  (stay tuned for a future blog post on cutting metal with lasers...)

It's taken a bunch of tweaks - but I can now reliably produce boards that are good enough to be used with 0.1" DIP components.

All is revealed in this video:



Quick summary (step-by-step / more details in video):
1. Attach .001" steel shim to cast acrylic sheet with mounting tape (leave paper backing on acrylic)
2. Cut out though-holes and board itself at 6.5 mm/s (2 passes)
3. Cut traces at 15 mm/s (2 passes)
4. Peel off non-trace segments from board surface (including tape and paper backing)
5. You have a circuit board!

Pros:
Fast - can make a simple board in only a few minutes
No chemical etching needed
Boards can be any color acrylic comes in - including transparent!
Laser can be used to cut through-holes / cut the board out in any shape

Cons:
Steel isn't a great conductor / may be an issue for some circuits
Boards are not as sturdy as etched ones
Traces limited to minimum of around 1/16" wide - not suitable for SMD
Soldering smaller (DIP) components can be a bit finicky

Click here to download the SVG for the 555 LED flasher

555 LED Flasher Circuit Details:
+Vin: About 3v (depending on LED)
R1: 10k ohm resistor
R2: 10k ohm resistor
C1: 33uf electrolytic capacitor
LED: An LED

This board was manually designed in Inkscape.  I'm very interested in how it goes if anyone tries this process with a board designed using EAGLE or other real software. 

If you try this project - please post your own tips / tricks here!

-Rich

PuzzleCut OpenSCAD Library

I just put together an OpenSCAD Library - PuzzleCut - http://www.thingiverse.com/thing:35834

It lets you easily cut objects into 2 or 4 (theoretically as many as you like) interlocking pieces for 3d printing or laser cutting.

I created it after realizing a project I was working on wouldn't actually fit on the bed of my soon-to-be-shipped Replicator 2.

There are a few other tools that do similar things - but they didn't have the flexibility I wanted.

A few features:
Position puzzle cuts anywhere on X and/or Y axis.
Adjustable cut size
Adjust kerf for tighter or looser fit
Easily render individual puzzle pieces for export to STL

Code should be easy to tweak if you want more than 4 puzzle pieces / different angles / or bunny-rabbit-shaped cuts.

Enjoy!

Fix the Fresco

Apple finally approved my new app (for iPad and iPhone), Fix the Fresco:

http://itunes.apple.com/app/fix-the-fresco/id557433478?mt=8
http://www.nothinglabs.com/fresco/

It took them 11 days to approve it - reducing the prospects of building any inertia with the news story fading...

  

Can you fix the damaged Fresco?

In Borja, Spain an elderly churchgoer attempted to restore a cherished 19th century fresco damaged by time.

Her well-intended efforts left the fresco severely disfigured.

Can you do any better?

Use 4 different brushes and colors from the actual painting to restore the fresco.

Start with the damaged fresco - or for a real challenge - try to correct the botched restoration!

Includes views of the original undamaged painting, fresco with damage and the botched restoration.

Share your restored fresco with others via Twitter, Facebook or email!

Tub Mate - Dry Ice Carbonated Yerba Mate

I finally got around to publishing my recipe / instructions for "Tub Mate" on Instructables.

For those unaware - Yerba Mate is a caffeine containing plant used similarly to tea or coffee by many South American cultures.

I have become a fan of a carbonated soda version from Germany - Club Mate - and decided to take a stab at brewing my own.

This version of mate is carbonated using a very small amount of dry ice as opposed to the usual equipment.

Check it out:
http://www.instructables.com/id/Tub-Mate-Dry-Ice-Carbonated-Yerba-Mate/

Please follow the instructions - otherwise you might die.

LaserTweet - Twitter Projecting Laser Show

A little over a year ago I shared my Arduino Powered Laser Show on Instructables.

LaserTweet is a modification of the laser show that uses a Python script to search Twitter for tweets with certain hashtags - and then display them.

I've also put together an instructable for it at:
http://www.instructables.com/id/LaserTweet-Twitter-Projecting-Laser-Show/

Plan is to show it of at toorcamp in a few weeks.

The "home" for both projects is at:
http://www.nothinglabs.com/laser/