if you could recall my old FM
transmitter tutorial you may have
noticed I love using pre sensitized PCBs
it's an awesome type of PCB that
requires a fluorescent lamp and a
kitchen timer for photo exposure years
later I built an automated exposure box
for getting much more consistent results
in doing home fabrication of pre
sensitized PCBs this device is simple to
use and is equipped with exposure
control and an automated countdown timer
an LCD displays all the settings and the
time remaining for exposure once the
time runs out it turns off the light
source and prevents you from having
overexposed PCBs if you want to learn
how to build quick and easy high quality
PCBs at home feel free to watch my
comprehensive tutorial on single sided
PCB fabrication here are the things that
you will need you can find them from the
links from the descriptions below the
main components of this project as an
Arduino Nano and some LED strips to
reduce the work in making a wooden
enclosure I decided to use an orican
plastic container the next step would be
building an evenly lit light source I
ran into a problem with my containers
lid as it doesn't have a flat surface so
I decided to cut a rectangular piece of
cardboard and hot glue that to the lid
for my LEDs to rest upon use a pair of
scissors to cut the LED strips based on
your lids with these strips can be
soldered together later on next peeled
adhesives at the back of the LED strips
and ready your strips on a table this
would make the mounting process a lot
easier once done you can mount each of
the strips on your containers lid try
not to leave some gaps the more LED
strips the better more LEDs means more
light and more light gives you a faster
exposure time now solder all the
negative pads together on a bare solid
wire and all the positive pads on a
separate line this gives you a 12 volt
parallel connection for all your LED
strips using a bench power supply set it
up to 12 volts and connected to your LED
strip try to see if it grunts if it
doesn't there's probably Schwartz
somewhere in your solder joints now
let's prep our makeshift project
enclosure I decided not to use 3d
printing because I didn't want to scare
other hobbyist from attempting this
project as
started by using a ruler in the marker
for adding guides and cutting the door
I used the Dremel and a grinding disc
for cutting the larger plastic cutouts
as for the smaller rectangular cutouts I
used the mini drill and drill bit as an
improvised routing tool I use the Dremel
for the LCD cutout and a drill for the
potentiometers buzzer and button when
you're done with all the holes and
cutouts you can now mount the button and
the potentiometers use the provided nuts
and washers to fasten them in place snap
on the switch in the DC jack as well use
hot glue if you must
in this step you'll need to fabricate a
PCB if you're new to PCB fabrication you
can check on my tutorial by clicking on
the link below however if you choose to
use a perf board you can download the
schematic diagram as a reference
everything you need is in the file
package this includes the schematic
diagram the parts placement diagram the
Gerber files the Arduino codes and the
PCB layout when you're done fabricating
the PCB just follow the parts placement
diagram and solder all the components
accordingly I usually use my duct tape
as helping hands while I'm out the
components I started with the two
jumpers the 10 kiloohm goes here the 100
ohm goes there and the 470 ohm goes
right over here then I added a tantalum
trimmer then bent the TI P 31 C NPN
transistor in place next I soldered the
pair of male headers to the Arduino Nano
then snapped it in place I then soldered
all the components using me do it
yourself hako soldering station and yes
it's part of my upcoming tutorials next
you'll need to solder a 16 pin male
header for linking the board to the LCD
just a reminder the male header should
be pointing outwards from the copper
side of the board you can push the black
plastic of the header downwards if you
want the LCD to be a bit closer to the
board
I also soldered some male headers as
contact points for the external
components this would help a lot in
wiring the external components later on
finally he can solder the headers to the
LCD thus forming the link instead of
using screws you can use hot glue to
quickly mount the assembled LCD timer to
the enclosure and that's just perfect
potentiometers have the tendency to
rotate when the nut loosens hiding hot
glue fixes the problem to make the
project look nicer
added some plastic knobs for the two
potentiometers and then wired everything
to the main board this includes the
piezoelectric buzzer the potentiometers
the button the power switch and the DC
jack next you can power it up by
connecting it to a power brick created
at 12 volts 2 amps if you want to make
it portable you can connect it to a
regulator and some batteries then hook
your power source to the DC jack it's
now time to upload the firmware bring
out your laptop and your laptop would do
you can also check out my review for the
huawei mate book D 15 anyway connect the
mini USB cable to your USB port and TR
Dino nanos mini USB port the Arduino
codes can be found from the file package
that I've uploaded go to the tools tab
and select your Arduino board I'm using
Arduino Nano for the processor select
this one and for the port select the
last port and now you can press this
button to compile and upload the Arduino
program you'll know it's successful when
it says done uploading we're not done
just yet you still have to adjust the
LCD contrast use a screwdriver and turn
the trimmer resistor until the text
becomes clear using it is quite simple
here's how you use it first turn on the
power switch the LEDs should start
glowing when it's all lit and booted you
can now place your per sensitized PCB
together with your printed layout for
the brightness I usually try to turn it
all the way up as for the duration for
LED strips it averages on around 10
minutes I suggest experimenting with
sample boards around that range until
you find the best exposure time that
works well for you
the LCD displays the time remaining left
there are also bars below to show you
the progress once the time runs out the
LEDs will turn off to prevent
overexposure to reset the timer just tap
on the button once again with this you
get to have more consistent outputs on
fabricating your own PCBs if you liked
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thanks for watching
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