After building my 6 DOF robot arm, I needed a way to control it through the PC using a Qt graphical interface. Having already developed my Qt-Arduino interfacing class, I decided to up the complexity of the project by using an Arduino Pro Mini, instead of an Arduino UNO.
As you can see, the pro mini is and come without headers pin, so it can be customised into whatever configuration you like.
So, to control my robot arm with a Mini Pro, I would need to design and fabricate a 6 servo controller circuit that would connect to the PC over the serial communications line and translate commands to servo motor impulses that would activate the robot.
I started by designing the circuit using Fritzing. All I really needed was to tap output from the 6 PWM capable pins on the Mini Pro to a sort of “Array” of 6 servos. I also added some blank female headers (just in case I needed to upgrade sensors/ control later on). Power supply is connected to the Arduino’s RAW pin. A 6 pin female header provides connectivity to the PC through serial interface.
After completing the design, I printed it out on a laser printer. and prepared a copper cladded PCB board by cleaning thoroughly, sanding with 400 grit paper and cleaning again with iso-propyl alcohol.
I placed the printout on the PCB board and using a hot iron, transferred the toner ink. The iron needs to be set to its highest setting, and you need to make sure that the heat and pressure are applied evenly and thoroughly for at least 2 minutes.
Once it cools, the paper should be stuck to the PCB board. Place them in water, and after a few minutes, the paper can be pulled away. Any paper residue can be cleaned off with an old toothbrush.
Check to see if all the lines have been transferred correctly. If not, use a thin permanent marker to fill up any gaps. Place the board in Ferric Chloride solution and gently agitate every 5 mins or so. If you are making the solution from crystals, be careful….the reaction is exothermic and will generate heat and steam when the crystal touch the water. Its good idea to use gloves and avoid contact with the solution.
Now clean away any solution on the board with water and gently clean off the toner ink with acetone solution (not mandatory) and a scrubbing pad. This will leave only the copper tracks behind, ready to drill and solder.
Here is my final circuit board, with the Arduino Pro Mini in place.
I decided to get a little creative and etched an ambigram “Korulas” logo on the PCB as well. Save the image and flip it upside down…it reads “Korulas” both ways!!