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JOSE'S ELECTRONIC CALCULATOR
   
   
A BIT OF HISTORY
   

So, as the story goes, some 30 somewhat years ago, after my father had lost his job and with Christmas nearing he decided to manufacture Christmas gifts for his 3 children

The years was roughly 1973 and as I recall it he built a 3 story Barbie doll house for my older sister (with elevator and all), a Log Pig (on wheelers) for my younger sister, and for me a curious electric box with an engraved plate labeled "Tonio's Electronic Calculator)

Although.... "Electronic" might have been a bit of an overstatement. I do recall rapidly falling in love with the curious box full of lights and switches.

It was composed of two handcrafter 7 segment LED (like) boxes, and a series of switches that would enable the user to create different numerical characters ranging from 0 to 9

I remember turning off the lights to my room and plugging in the fascinating box and spending hours and hours trying to memorize the sequences, sometimes inventing a few of my own to create strange characters

After many years of growing up, enough confidence was gained to open up the box and start deciphering its mysterious ways, the basic layout were a series of wired Christmas bulbs (the larger 110V variety). Much in the spirit of Christmas he chose to use red bulbs for one of the 7 segments and green for the other

When the main switch was turned on, the diagram below the segments would light up enlightening the user as to which switches to flip to create the numbers, accordingly when the switches where flipped and only after pressing the magical "activate" button the segments would light up revealing the results.

Throughout the next 30 years the mysterious box was lost in time and space never to be seen again, although I was always left with the nagging desire to play with it again.

Move forward to the year 2011 in which it occurred to me that with my very elemental knowledge in electronics and circuit board creation I should be perfectly qualified to reproduce the project at a smaller more compact and efficient scale… and my Fathers birthday approaching in April would serve as an extra incentive to surprise him.

 

THE PROJECT (all photos can be right clicked and saved)
   
Step 1, the Design.

In My case I simply use Microsoft paint (NOT WINDOWS 7 Version) although there are much better applications out there designed for circuit board creation





Once the original design is completed the drawing must be flipped Horizontally as to creating a "negative" that we will use in the creation of our Printed circuit board, it is also recommended to convert to Black and white as to create a better impression on to the final board before etching

once we have the image just the way we want it, we must select the proper paper on to which we will be printing, after reading a whole bunch on this and reviewing my previous notes, I tried using simply cheap magazine glossy paper as shown in the photograph on the side





NOTE: Ultimately the best paper I found was from staples (PHOTO SUPREME) for Laser Printers,  , although photographs of process where created while testing on magazine paper

 MAKE SURE YOU GET LASERJET COMPATIBLE PAPER,  OTHERWIZE IT WILL MELT INSIDE YOUR PRINTER


Once we have selected proper paper, we must print ON A LASER PRINTER, the "Mirror image" of our design to be hard pressed onto a copper coated project board, it is EXTREMELY important to remember to flip the image before printing, we MUST use a NEGATIVE so after the pressing you end up with a positive.





Once we have our page ready to be pressed, it is time to begin the project board preparation, I purchased my project boards on eBay, Auction was for "8 pcs. Copper Clad Circuit Board Single Side PCB 4 x 8"







In preparation for pressing, the blank board must be thoroughly cleaned to ensure, our negative will "stick to it properly" as shown here I use regular Dish washing detergent, in a plate with water to begin the cleaning process





After allowing the the board to soak for a couple of minutes, I use a "scotch bright" pad to  thoroughly scrub the board removing any grease or other impurities from it







Carefully remove the board from the cleaning station, and rinse it off with plain tap water, it of of utmost importance NOT to touch the surface with your fingers, as even the slightest amount of skin oil can ruin the stamping process





Use a paper towel to dry the board without touching its surface, again extreme caution not to pollute the surface of the board, after drying I usually use a compressed air can to blow off any remaining derby from the paper towel.






We must now align our printed surface with the copper coated side of the project board, if you pay close attention on my design I included a hair thin line in my design to allow me to properly align up the printout with the project board





As shown in the image, I have aligned the printout to the circuit board and laid it flat on my "heating press" I am in the process of covering it with a towel so the paper does not stick to the upper portion of my press




The press shown here, is a standard T-Shirt image pressing unit picked up at a garage sale somewhere, I was fortunate enough to have one handy, but most people simply use a regular household Iron, I have also read of people using metal plates held together with four bolts and screws placed in a conventional oven to heat up and press the image





Press, pressure was set to maximum intensity, heat in between 250 and 300 degrees, and we set our kitchen timer to 25 minutes

Once the timer goes off, I unplug the unit and let it slowly cool down for another 30-60 minutes




Once the press is released, the paper should be very well firmly stamped (AND STUCK) to the paper, this is where it gets VERY tricky, I spent weeks perfecting the technique to get the perfect impression, if you read above you will know ultimately I used the STAPPLES LASER PHOTO SUPREME Paper to achieve my final results






Ultimately best results where to soak the board, (paper and all) in hot water, for this I used the same washing dish I used earlier, filled it up 3/4 with water and microwave it 3-4 minutes, left it soaking 10 minutes & afterwards, while pouring hot water directly from the tap in between the paper and the project board I gently started peeling back, ultimately this provided a near perfect impression on the board, Here you can see I am examining with my magnifying lamp

Although with my final release this was not necessary you do have the option of filling in any poor impressions on the board with a standard fine tip sharpie

I repeat if you use the STAPLES LASER PHOTO SUPREME paper you should end up with a PERFECT impression on the board

 MAKE SURE YOU GET LASERJET COMPATIBLE PAPER,  OTHERWIZE IT WILL MELT INSIDE YOUR PRINTER







Next we need to create our
"Circuit board Etching Solution"
I tried high and low to purchase this premixed, but ever since Radio Shack stopped selling their board etching kits it seems hard or expensive to but.

Ultimately the solution is easily accomplished by combining "Muriatic Acid" with "Hydrogen Peroxide 3%"


the proportion is (ONE cup of Muriatic Acid) to (TWO cups of Hydrogen Peroxide 3%)

I Used a laundry detergent cap to do my measuring, anything PLASTIC should work fine as the acid does not appear to have any effect on plastic

later ill show you what happens if you do this wrong.







Once our solution is prepared in a PLASTIC container, we are ready to dip our project board into it to etch away the remainder Copper and create a circuit board.

 NOTE: you SHOULD DEFINETLY use rubber gloves while handling these chemicals, also do it outdoors in your backyard where there is good air flow, the fumes are extremely toxic and the acid will burn your skin.



Drop the board into the etching solution and hold the container within your hands, some people recommend putting it on something that vibrates but this is way to painfully slow..  for m taste, I gently sway it back and forth. ensuring the acid is etching away evenly at all the board, swaying the acid from one side to the other, paying special attention to the areas where effect is slower (mostly areas with large concentration of ink or "toner" in this case)

 




As you can see in the photo, as the acid washes over the copper coating it will start "eating away" at all of it except what is protected under the image we have pressed on to it, hopefully at the end we will have a perfect circuit board to work with




THIS, is what happens if you get your proportions wrong, in this example I inverted my proportions and used TWICE as much acid, as you can see the results where catastrophic for the board

REMEMBER CORRECT MEASSURE
1 PART: "Muriatic Acid"
2 PARTS: "Hydrogen Peroxide 3%" 

 


 		 In this example I DID use the proper proportions and as you can see all the copper has been etched away and our design remains intact and safely guarded under the printer toner we impressed on to the board

Here I have carefully removed the board from the etching solution and rinsed off with the garden hose



 
to clean off the toner and reveal our circuit board we use 100% Acetone purchased in any pharmacy, I tried using the girlie nail polish remover which did NOT work very well, I also found that the cotton Scrubby pads do the best job, MUCH better than paper towels 

 


 		 Here you can see the finished board, all cleaned up and ready for the next step.

Notice, because we used a NEGATIVE while imprinting on to it the result is a POSITIVE board.





 
Under close examination you can see my original design included tiny PIN SIZED HOLE GUIDES on the portions of the board where components are meant to be soldered on to, this will aid in the positioning and drilling of these holes before mounting the actual components




 

 


 		 Here, my Lovely assistant is drilling the component holes into the circuit board to allow me to start mounting the components, for this we used a standard Dremel (like)  tool and a Dremel drill press, both can be purchased through Amazon or your local hardware store

Dremel Tool
Dremel Workstation Press


Once all the holes on the board have been drilled out we can start soldering on our parts, for this I purchased a variable heat soldering Iron from Radio shack with a fine tip, I also used SILVER based fine solder.

the Micro switches and LEDs were all purchased on eBay, most of them took over a month to get here as they came from china



Almost done soldering on all the micro switches with their corresponding resistors, almost time to solder on the LEDS.









Here all the LEDs have been added to the board

I used 480 Ohm resistors in order to be able to use a 12V AC Power supply, which I find to be most common


  
 


 Power cables attached and ready to try initial on/off test, notice I added miniature cuts of translucent rubber hose around the LEDs to add to the effect





A few minor adjustments we had already anticipated in the original design to ensure both sides of the display work with the same switch combinations





  

 


We examine the back to ensure there are no shorts and everything is nice and tidy






Initial tests indicate everything is working





Now that we have a working prototype, we must add the diagram that illustrates what switches to flip to generate what numbers, this was done using the original circuit design as a template to ensure the holes are exactly in the right spots.







Plexiglas from your local hardware store should work perfect as the front of the unit, Taped the Diagram over the Plexiglas as to drill the holes in the right spots.

 used same Dremel press to drill the holes



Perfect FIT





We must also ensure after adding the Plexiglas, none of my contacts came lose and everything is still working



To build the wooden enclosure I had to purchase a new Table saw as the motor of my old one decided to "seize up" the day I intended to build the box.





I made Sure to add Plexiglas to back and front of the unit as to show of our handy PCB craftsmanship from the back side
   
   
YOUTUBE VIDEO


   
   
   
ALL PHOTOS IN 640x480 RESULUTION DOWNLOAD