The
Premiere source for Computer Professionals I Claim affiliation with nobody,
this site exists because it amuses me
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.
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
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
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
