Intro: Mini LED Spot Light for Computer Case or Other Flat Surface
This miniture LED spot light can add a warm glow and brighten up the look of your computer case. It's small and round and can be mounted nearly any where inside a case. The circuit board is just slightly smaller than a penny yet has plenty of room for six 3 mm high intensty blue LEDs. The circuit is mounted in a plastic base that can also be mounted just about anywhere you can think of. A simple and fun soldering project for beginners.
Step 1: Parts & Materials
6 each 3 mm LEDs - High Intensity Blue, Water Clear Lens, 3.3 volts, 20 ma.
2 each 100 ohm resistors, 1/8 or 1/4 watt (Use 150 ohm resistors if connecting to car.)
5/8" Round Circuit Board (The smallest board in Radio Shack #276-004.)
Power Connector - Such as from an old computer case fan.
Air-Tite 16 mm Coin Holder
Clear Epoxy Glue
Double Sided Mounting Tape
Wood Craft Stick & Piece of Cardboard for Mixing Glue
15 Watt Soldering Iron & Solder
Wet Sponge for Cleaning Soldering Iron Tip
Small Wire Cutters
Needle Nose Pliers
A vice with alligator clips to hold the circuit board while soldering is helpful but not necessary.
I bought the LEDs from mouser.com for less than twenty-five cents each and the resistors for a nickel each. I bought the Air-Tite coin holder from shawneecoin.com for about a dollar. The coin holder was for a coin but I found that it added a nice finishing touch and made it simple to mount the light to any flat surface. The power connector that I used to make this project with was a left over fan adaptor from a new computer case fan.
Step 2: Solder the Resistors to the Circuit Board
The circuit wiring is fairly simple. There are two circuits wired in parallel. Each circuit consists of one resistor and three LEDs. The power (12 volts) for each circuit is connected to the resistor then the resistor is connected to three LEDs wired in series.
Insert the resistors into the circuit board as shown in the pictures. Use masking tape to help hold the resistors in place while soldering the leads.
Notice that two of the leads will have a common connection when soldered in place on the board. Bend the one resistor lead toward the other set of common connecting rings and solder the leads as shown.
Soldering Tips: Touch the soldering iron tip to the lead and to the ring on the circuit board for just a moment and apply a small amount of solder at the same time. The solder joint should be a bright silver color and not a dull gray. Keep your soldering iron tip clean by wiping it on a wet sponge. Excess solder can be removed from the circuit board with a desoldering tool. Use needle nose pliers to hold work. Do not touch any of the wire leads while soldering as these get very hot and will burn your fingers. A small vise is also very helpful in helping to hold your work secure.
Clip the bent resistor lead using small wire cutters leaving about 1/4" as shown in the picture.
Do not clip off the entire lead. You'll need to solder this to the next connection.
Bend the clipped wire lead and place the tip into the adjacent double copper ring, as shown.
Solder the clipped lead in place. This is also where the positive lead from the power connector will be attached. Trim off any of the excess lead from the top side of the circuit board. Clip off the other resistor lead that is soldered to the board.
Step 3: Solder the LEDs to the Circuit Board
The LEDs are installed in much the same way that a set of batteries would be installed in almost any portable device with the positive (+) ends connected to the negative (-) ends. The first positive LED lead (the long lead) will connect to the resistor then the negative LED lead (the short lead) will connect to the positive lead on the next LED. Then the next negative lead will connect to the next positive lead. Study all of the pictures in this step and become familar with the circuit before soldering.
Make sure the resistors are in a vertical postion to the circuit board and bend the leads on the bottom side of the circuit board as shown.
Insert an LED as shown in the pictures. Position the LED so that the long lead will get soldered to the resistor lead.
The LEDs should be mounted 3 mm to 4 mm above the circuit board. Use masking tape to help hold the LED in place while making the first solder connection.
The LEDs in this project were postioned facing straight up. If you would like to bend the LEDs at different angles then bend the leads and position the LEDs before soldering them to the board.
Solder the short lead of the LED to the board first to hold the LED in position and to make sure of placement. Do not trim this lead yet. It will get connected to the next LED.
Solder the resistor lead to the long lead on the LED. After soldering, trim the excess wire leads from this connection with wire cutters.
Insert the second LED with its long lead next to the first LED's short lead.
Solder the short lead of the second LED to the board to hold it in place.
Then bend the long lead from the second LED over so that it touches the short lead of the first LED, as shown, and solder together.
Insert the third LED and position the long lead next the the previous LED.
Solder the long lead of the third LED to the short lead on the second LED.
Do not trim the short lead of the third LED. Trim other connections as shown in the picture.
Now add the LEDs to the other side of the circuit board. Begin by inserting an LED, as shown, with the long lead installed next to the resistor lead.
Repeat the same process as above to install the remaining LEDs being sure to connect the next long lead to the previous short lead on the board. Do not trim the short lead of the third LED.
Bend the two remaing short leads so that they touch as shown in the picture. This is where the ground wire from the power connector will be attached.
Step 4: Solder the Power Connector
Prepare the ends of the wire leads from your power connector. Strip about 3/16" insulation from each lead.
Tip: If you are using a computer power connector that has four wires then use the yellow wire and the black wire closest to it.
Solder the wire leads from the power connector to the locations shown in the picture.
After soldering trim off the excess wire leads from the LEDs and the power connections.
Step 5: Glue the Circuit Board Into the Plastic Base
I had an Air-Tite 15 mm coin holder on hand and used it for this project. It fit just a little snug and so I think a 16 mm coin holder may work just a little better. An Air-Tite coin holder with a black gasket ring, instead of the white one that I used, may not show as much dust and dirt after the LED light has been used for a while. These are available from shawneecoin.com for about a dollar each.
There are three parts to an Air-Tite coin holder, the lid, the base, and the gasket ring. The gasket ring fits around a coin then fits inside the base. The lid then slips over the top. This project uses only the base and the gasket ring.
Place circuit board inside foam gasket ring and test fit inside coin holder base. Then remove circuit board and ring from base.
Mix a small amount of clear epoxy glue. Apply glue to the inside of the base. Use enough glue to just cover the inside of the base.
Before the glue begins to set up, place the circuit board in the foam ring and set it inside the base on top of the glue. Press down around the edges of the foam ring. The edge of the foam ring will stick up above the base about a millimeter or so and that's normal. Excess glue will ooze up through the holes not used on the circuit board.
Apply more glue to the exposed leads on top of the circuit board. This is to help protect the bare leads from touching anything.
The epoxy glue begins to set up in five minutes so work quickly. The glue will also be a little bit runny before it sets up so protect your work area from spills.
Allow at least an hour or more for the glue to dry before handling.
Step 6: Using the Light
The LED light assembly is light weight and can be mounted to almost any flat surface using double sided mounting tape. Just cut a small piece of double sided tape then peel and stick.
After mounting the light in a computer case use a small wire tie to secure the power wires to the case frame near the light in case the double sided tape gives out. You don't want the light to fall down on your motherboard. Use good common sense when mounting the light. If there is a possibility that an exposed wire lead may touch another piece of metal then add a small 1/2 amp fuse to the power lead.
Connect the power connector and enjoy the bright blue spot light! :)