A Few Tips & Tricks: Arduinos, PCB Tricopter Frames, Home-made Acid Etchant for Copper

By: Gabriel Staples
Written: 28 May 2013
Updated: 30 Oct. 2013
-added link to LadyAda's Arduino Uno FAQ
-added link to Arduino Nano V3.0 on Ebay

Other Articles You May Be Interested in Reading:

• Getting into Scratch Building - 20+ Planes with ONE Motor & ONE Power Pod!
• Beginner RC Airplane Setup
• Thunder AC680/AC6 Charger & Computer Data-Logging Software
• Parallel Charging Your LiPo Batteries

So, this month I've been dabbling into a few new RC airplane areas that I have previously not looked into.  You may wonder how these topics in the title relate to RC airplanes?  Well, for me, everything does :), so let's briefly discuss:

Arduino & Microcontrollers:

What is Arduino?  Well, Arduino is a small interface board which connects to your computer via a USB cable, and consists of an Atmel microcontroller chip, or "brain," which can do a variety of functions and processing, as well as circuitry to enable you to connect to it via a USB cable, in addition to a voltage regulator and input and output ports.  Basically, it is a development or experiment board which allows you to plug in sensors and circuitry and do anything you can imaging via your own personal ingenuity and programming skills---yet it is inexpensive and simple enough that anyone can get started.  It is especially designed for the non-programmer.  Here is Arduino's description of themselves.  A few things that make Arduino unique are its price, ease of use and programming, and the fact that it is open-source.  Open-source means that its parts, pieces, construction, and coding are all available to the public, and that its software is FREE.  This is the counterpart to "proprietary," which means that something is owned by a company and its internal workings are generally guarded and kept secret in order to prevent others from duplicating it.

You might not know it, but the microcontroller, or MCU, which is the heart of the Arduino, is a very common-place item in today's electronics.  Modern RC radio transmitters use them, for example, as well as ESCs (Electronic Speed Controllers) and "smart" battery chargers such as the Thunder AC680.
 Many UAVs (Unmanned Aerial Vehicles) use microcontroller-based autopilots!  Now, with Arduino,
you can put this computing power into your own hands, and by following online tutorials you can make it do anything from blinking an LED to having it automatically send you a text message or email whenever someone walks past a motion sensor.  I am planning on using one to create an altimeter and datalogger, as well as a current sensor and datalogger.  All of these things are easily possible.  Arduino microcontrollers are exceptional also in their prices, as they can cost as little as $10 on HobbyKing, or ~$22 on Amazon!  I recommend you get on Amazon now and do a search for Arduino just to see some of what is available.  

Though I am a brand new Arduino hands-on user, I’ve done a lot of online research on it and seen many amazing projects done with it.  Arduino is a very powerful tool, and will certainly enhance any engineer’s skill-set as well and make them a much better engineer.  It will also open up a whole new world to RC hobbyists and enable you to do virtually anything you can imagine but didn't otherwise know how to make happen.  Below, you will see many links.  The tutorials in the links range from very simple (blinking an LED) to very complex (sending you an automated email when someone walks past a motion-sensor). 

• Arduino homepage:  http://arduino.cc/ 
• More Information on Arduino
• Arduino Uno FAQ by LadyAda
• Examples of where to purchase:
• Arduino Uno on Amazon, $21.95.
• Arduino starter kit on Amazon, $31.99.
• Arduino Mega on HobbyKing (this is a FANTASTIC price), ~$20.  
• Arduino Ethernet Shield on HobbyKing (allows you to connect your Arduino to the internet, but requires a separate stand-alone Arduino board), ~$18
• Here it is on Amazon for $28.50
• Arduino Ethernet on Amazon, $56 --this is the stand-alone version of the entire internet-capable Arduino & microcontroller interface board--no separate Ethernet Shield required!
• Arduino-based Autopilot on HobbyKing, $76
• Arduino Nano V3.0 for <$9 WITH SHIPPING, on Ebay! (Note, in case the link goes bad when the listing ends, the name of the listing is "Mini USB Nano V3.0 ATmega328P 5V Micro-controller Board For Arduino-compatible," and I've seen this same one sold by sellers "axeprice" and "comelili.").  I own this one, from Ebay, and it works great!  The nano has all of the same features as the Uno, except it is smaller is all.  

• 
  
• and many more; Google it!
• USBasp AVR(Atmel microcontroller) Programming Device (you don’t need this to get started, but you will need it to reload the bootloader onto an Arduino, which is sometimes necessary, so I *highly* recommend it!)
• FREE Online Tutorials:
• THESE LOOK VERY GOOD: http://www.ladyada.net/learn/arduino/index.html
• More tutorials-ALSO LOOK VERY GOOD (including an Arduino selection guide, and lessons 0-17): http://learn.adafruit.com/category/learn-arduino
• Books: 
• Programming Arduino Getting Started with Sketches[Paperback], by Simon Monk, $11.29
• Arduino Cookbook, by Michael Margolis, $27.23
• Electronics: you’ll need a breadboard, jumper cables, LEDs, resistors, etc, according to the project you are working on, or what you want to experiment with or try on your own.  Amazon and Radioshack have some great stuff to get started with Arduino.  However, hands down, the cheapest prices I’ve ever found for basic electronics like resistors, breadboards, jumper wires, capacitors, transistors, voltage regulators, etc, are from Chinese or other Asian vendors on Ebay when you use the “Buy it Now” option.  You can even add stuff to a shopping cart on ebay and pay for it all at once.  Note: these are NEW items on Ebay, NOT used.  Many people don’t know that eBay is beginning to function more like Amazon now in the sense that there are stores and vendors on Ebay selling new items.  Their prices are incredible.  For example, I got a pack of 600 assorted resistors on eBay for ~$3.50 with FREE shipping.  A similar item on Amazon is >$9.  These prices for basic electronics easily (usually) beat RadioShack, Amazon, Digikey, Mouser, etc.  The advantage of Amazon is shipping time.  Ebay items usually take 3~5 weeks to arrive, whereas Amazon items can be there in 2 days.  Your choice.
• Arduino-based Autopilot, called the "ArduPilot."  (The online user manual wiki is here:  http://ardupilot.com/). Get your vehicle to navigate autonomously.  Also check out diydrones.com and click on --> ArduPlane, ArduCopter, and ArduRover to see or purchase airplanes, multirotors, and ground vehicles all controlled autonomously using an Arduino-based autopilot.  You can also purchase an "ArduPilot"-based autopilot on HobbyKing for only $76 here!

PCB (Printed Circuit Board) Tricopter Frames:

As of late, I am working on a tricopter frame.  I am following, somewhat at least, David's fantastic tutorial here, which uses a PCB frame from his earlier tutorial here.  In order to do follow his steps, I did some research and purchased the cheapest PC Board money could buy.  I found it on Ebay.  I got 5 pieces of 10x15 cm, 1.5mm thick, PC Board, here for only $8.99 with FREE shipping.  You can find it by clicking the previous link, or by searching for the words "5pcs 10 x 15CM Single-sided PCB" on Ebay.  When I got to David's step which said, "To remove weight I etched away the copper from the glass fibre laminates," I thought that this sounded like a good idea.  I also wanted to remove the copper in order to minimize any interference that might occur with my receiver or telemetry transmitter.  However, I was ignorant and thought that to "etch" meant to scratch away with a knife.  After unsuccessfully attempting for a few minutes to scratch or peel off the copper with a knife, I did some research.  Three hours later I had discovered a few things and done a lot of reading and learning.  I learned that 1) Etching in this case means "to chemically dissolve."  2) Ferric Chloride is the most common etchant, and is available from Radio Shack for only $11.49 here.  If you use this to etch away, or dissolve the copper, do *not* throw away the used copper etchant solution.  It is a hazardous material and cannot just be disposed of on the ground or in the sink or toilet.  Rather, put it back in the bottle and reuse it again and again.  Eventually it will lose its effectiveness and you'll have to properly dispose of it and buy more.  3) Why use Ferric Chloride, which costs $11.49 for 2 measly cups, when I can instead make gallons of infinitely reusable copper etchant for the same price? Not only that, but it's more fun to make my own etchant.  That leads me to my next topic:

Home-made Hydrochloric Acid and Hydrogen Peroxide Copper Etchant Solution

I discovered this fantastic tutorial here on instructables.com:  Stop using Ferric Chloride etchant! (A better etchingsolution.) by The Real.  I then went to Home Depot and bought Muriatic Acid (or Hydrochloric Acid; see Wikipedia here) (costs ~$13 for 2 gallons), and I went to Wal-mart and bought hydrogen peroxide in the pharmacy section for $0.88 for a large bottle.  I cut the top off an old laundry detergent bottle to use as a soak-pan for the PC Board, and I got an empty and rinsed milk jug for the storage container of my etchant.  I poured 1 part (2/3 cup in my case) hydrochloric acid into 2 parts (1 1/3 cup in my case) hydrogen peroxide, in the laundry detergent bottle, then placed in the PC board.  It immediately began to bubble and fume.  I did NOT do this indoors.  The solution is VERY powerful and harmful.  I did it outside in my driveway.  I wore rubber gloves and had on safety goggles. DO NOT BREATHE THE HYDROCHLORIC ACID FUMES.  THEY ARE VERY STRONG.  With some gentle agitation, the copper was all dissolved in only 6.5 minutes or so.  I am storing the solution in my garage, as it is capable of dissolving virtually all metals, including nails and copper, and aluminum too from what I've read, and I don't want it in the house.  It also seems to dissolve asphalt.  

Now, I have a pretty green solution for future use dissolving more copper!

PLEASE POST ANY QUESTIONS OR COMMENTS BELOW.