Have you ever wondered on how to make your girlfriend happy and simultaneously keep the conventions of nerdiness? Why not use your geek powers, to make the ones you love happy!
A few Days ago, I was sitting on my bed, staring at a bottle of Iron III chloride, which I bought about three months ago. Since then I didn´t touch it again, because I had many doubts concerning the use of chemicals like these on the same table, that I eat on three times a day…
Now I decided to take the risk, because the chance to get away from stupid strip boards seemed to be more than worth it. Okay, an exposure unit with UV LED´s was already built (an article about that will follow soon), so I just had to start. After clicking together a simple test Layout with different structure widths, I directly had the wish to do something cool with that. So I thought about dedicating my first self-etched PCB project to my girlfriend :-)
Because I have never worked with SMD parts before, I decided to kill two birds with one stone and use them for a heart shaped LED arrangement. I now started with my test layout to figure out the exposure, development and etching times.
After having these results, I printed out my PCB layout with an inkjet printer on special inkjet transparency film. I did this two times, because the ink coverage wasn´t that good. After aligning and fixing both together, I removed the protective film from the PCB and took four little clamps to hold it all together. After 14 minutes exposing, I went on, putting the board into the development fluid for about 60 seconds. That looked very good so far (these little sprinkles were there from the very beginning)…
Now I started etching this thing. Using Iron III Chloride was my method of choice, because you can use this inside your room without the having any disgusting smells. I utilized a water bath, to bring it to its working temperature of about 40°C. After 20 minutes of moving the fluid, the board was done, and I was quite happy with the result (except from the test board, this was my very first try).
Now the fun part had to be done :-) I decided to use red PLCC-2 LEDs with ~700mcd and every LED should get it´s own resistor (330Ohm, 1%) to drive them with 5V. The soldering was easier than I thought and I think, SMD will be my choice in the future (okay, this actually wasn´t the smallest structure width :D). This is the assembled board.
After testing everything, I decided to add some extra spice to this, so the Adafruit Trinket I had on my desk came into play. I wanted the heart to fade in and out for having a more heart like effect. The tiny bit of code was written in no time and I now thought about hooking everything up. Hopefully for the last time, a little strip board was used, to hold a L7805CV Voltage Regulator (to power the LEDs with 5V separately from the Trinket) and a Mosfet (this for sure is bit of an overkill, but I had nothing more suitable laying around ;-) ) to control them. To switch this thing on and off, I came up with two tiny neodymium magnets (these have so be soldered carefully, as magnets loose their magnetic force if they get to hot). Now I put all things together in a plain white picture frame.
This was my little experiment on etching PCBs, my table still has nasty dark spots from the developing fluid :-) I´m looking forward to my next electronic projects, and I really recommend this method for prototyping and want to encourage all bread- and strip board users to give it a try :-)