A portable, battery-operated light source can be very useful when looking for quick, cheap methods of illumination outdoors (or indoors when an outlet is hard to come by). This instructable covers the design and fabrication of a portable light source that can run off a 9V battery for several hours.

This design is very straightforward and simple - all the materials that I used to build it cost about $10 as I bought all the components online.

Step 1: Materials

Required Materials
- Soldering Iron
- Solder
- 9V Battery Snap Connector
- 9V Battery Clip
- Wire (6 in. max)
- 3 10mm white LEDs (Super Bright preferred), 28000 MCD
- 3 220 ohm Resistors
- Breadboard-layout solder board
- Velcro Strips

Step 2: Circuit Layout

Lay out the components as per the circuit schematic. Due to the simplicity of this circuit, the circuit components can be laid out exactly as they look in the circuit schematic.

Once all the components are on the board, secure them by either taping over the tops of them to make sure they stay in place, or bend the leads going through the board to 90 degree angles to ensure they won't slip out when the board is turned over for soldering.

Note: The beveled (or flat) edge of the LED is the cathode which goes to ground. If the LED is reversed it will not light.

Step 3: Soldering

Fairly straightforward - all this step entails is the soldering of the components to the solder board. Be careful not to heat the pads up too much or the they may come off (especially on some of the cheaper solder boards).

Step 4: Overall Circuit Testing

Once the circuit has been soldered together completely - it makes sense to ensure the lamp is in working order before securing the 9V battery and clip to the bottom. The quickest way of doing this is to simply touch the 9V battery +/- leads on the appropriate leads of the 9V Snap Connector. If all 3 LEDs light up, the circuit was built correctly and the project can continue to finish.

Otherwise, analyze the circuit built on the solder board to ensure that current passes from the +V battery bus through a resistor, through the LED, and through the wire back to the -V bus back to the battery. If the soldering was a little rough there may be some cold solder joints or broken pads, which make breaks in the path for the current to travel. Ensure that the LEDs are facing the correct way with the beveled (or flat) edge going to the -V bus of the solder board.

Step 5: Battery Mounting

Once the circuit is verified as working correctly, use the velcro strips to attach the 9V battery clip to the bottom of the circuit board. Velcro provides a non-conductive surface when applied directly to the bottom of the soldered connections which will not endanger the circuit with a short circuit potential. The other strip of Velcro should be applied to the 9V battery clip.

By attaching the 9V battery clip to the bottom with velcro, the 9V battery can be easily removed from the underside of the circuit board while still being stable enough to act as a base for the light source.

Step 6: The Final Product (and Miscellaneous Notes)

There you have it! A very simple portable light source that can be used both indoors and out (just don't let it get wet).

- If you do not buy a diffused LED it can be diffused by roughing up the surface of the LED down with sandpaper
- You can directly Velcro the battery to the bottom of the circuit board, bypassing the need for the clip. However, new Velcro will have to be applied with every new battery.
- If you bought a longer solder board than you need, feel free to cut off the excess. Either do this by laying out the circuit on the printed circuit board first, drawing where the cut point should be, and then cutting it off, or just be careful about your cuts when all the parts have been soldered on.
-If you would like to add more hours of operation, the 9V battery can be substituted for a AA battery clip (1.5V per battery, typically 4 AAs in series) - however this will only supply the circuit with +6v, which means the resistor needs to be lowered to 150 ohms instead of 220. The typical AA battery has a higher Amp-Hours rating than a 9V, which directly equates to a longer lasting light.
-If you would like to add more branches of LEDs on the overall circuit diagram, go ahead! Just make sure to mirror the existing architecture for the current path - +V Bus -> 220 ohm resistor -> LED -> Wire -> -V Bus. The only effect this will have on the overall circuit operation is that it will draw more current from the battery, lowering the overall hours of operation per battery.