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Here are the parts needed for this tutorial:
- Enclosed 3 cell (AA or AAA) battery holder with on/off switch
- Flashing/Color changing RGB T1 3/4 LED
- Flux-core solder
- Soldering iron
- Wire cutters/strippers
- 13/64 drill bit
- Masking tape (optional)
- Spray-on Liquid Tape (optional)
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Open the battery holder and look at the upper left-hand corner (behind where the switch is on the other side).
You should see two welds (melted plastic globs) that are holding in place a cover-plate that spans the top
of the battery holder. Cut these off. Usually, they will easily come off with a knife or razor but some stuborn
ones may need sanded or filed off.
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Once the welds are removed or ground down, you should be able to remove the cover-plate to reveal the back of the switch.
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Remove the terminal plate that the red wire runs under so we can re-route the wires to where we need them.
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The terminal plate easily pulls out with a pair of pliers. Just pull it straight up.
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Unthread the wires from the hole in the case so we can re-route them. |
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Re-route the black wire so it runs from the switch, around the weld-post and down
into the center battery compartment. Route the red wire behind the screw-post
(you'll have to tuck it in with a thin-blade screwdriver or similar) and then down
into the center battery compartment. Leaving a little slack, pinch the wires
into the upper corners of the center battery compartment. We'll use this rudamentary
measuring to determine where to cut the wires. |
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Cut the wires about 1/4" from the pinches. |
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Replace the battery cover and mark the center of the battery case on the same side
as the switch. |
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Drill a 13/64 hole making sure not to go through the battery cover. |
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Test fit the LED to ensure the hole is the correct size. |
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We are now going to prep the LED for placement inside the case. At this point
it is important to differentiate the cathode from the annode on the LED. The
cathode is the longer of the two leads. If both leads are the same length,
the annode is the lead on the same side as the flat spot on the base of the LED.
We connect the positive wire (red) to the cathode, and the negative wire (black)
to the annode. In this picture you will notice that the flat side of the LED
is on the left side. Make sure you keep the LED oriented correctly during
the bending so you don't wire the LED backwards. If you do, it's not the end-of-the-world,
but you will have to un-solder and resolder the leads correctly.
Start by bending the leads of the LED away from eachother at the base of the LED.
Lay the LED in the middle of the center battery compartment. |
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Bend the leads at 45 degree angles toward the top of the holder so the LED and its
leads can fit inside the center compartment and the leads run right next to the
walls of the compartment. Trim the ends of the leads so there is about a 1/8"
gap between the top of the compartment and the end of each lead. |
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Strip about 1/8" of insulation off each wire of the battery holder. |
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Tin the stripped ends. These wires are most-likely aluminum so a solder with
a rosin core is recommended and make sure your iron tip is clean for good heat transfer. |
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Solder the tinned wires to the LED leads. Again, pay attention to which leads
are the annode and cathode so you attach them correctly. The lead coming from
the side of the LED with the flat spot on the base is the annode and needs connected
to the black wire. |
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(Optional)
Mask off all but the LED and the leads in preparation for painting with Liquid Tape. |
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(Optional)
Spray a couple of layers of Liquid Tape to fully coat the leads. This will
also double as a glue to help hold the LED in it's hole. As an alternate method,
you could use hot glue along the walls to isolate the leads and hold them in place.
Just don't go too crazy as the battery still needs to fit in there. Electrical
tape may work as well. |
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This is the result of the paint-job. |
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It is not necessary to put the cover plate we removed in the first couple of steps
back on but it does make it look more professional. You will need to cut off
about 1/8" of the separator tab towards the middle of the cover-plate to make room
for the wires we routed through this section. The plastic is soft so wire-snips
or heavy scissors will do the trick. It will stay in place with friction,
but a dab of glue on the weld-posts wouldn't hurt. |
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Add three fresh batteries and turn it on. Batteries should last about 3 days
(constantly on - that's 60 hours of run-time) before you notice the colors are not
correct. The blue and green dies in the LED require the most voltage so as
the batteries drain, the blue will dissapear, then the green, and finally the red
will fade away. If you've read any of my other LED articles you may have noticed
I broke the rule of always using a resistor to protect the LED. In this case,
the on time of each die of the LED is relativly short and the flashing circuit adds
an amount of resistance itself so we are fairly safe taking this route. If
you decide to use a 4 cell holder though (readily available at Radio Shack), either
use a dummy cell for one of the batteries, or calculate out a resistor and splice
it somewhere in the red wire (just because it runs through a good open section that
can easily accomodate the resistor. |