Make your own 9v LED light

Updated: Jan 16, 2008

This page found at www.geocities.com/csroberts/light.htm

This light runs on a 9v battery and has 2 ultrabright white LED lights. It has an on/off switch and one resistor, a little wire, and a case (altoids tin). You can use just about any case you want: a 35mm film case might fit all the components, but I recommend something bigger. The various altoids tins, square and round, seem to work fine.

If you bought a kit from me you will get these components:

You will need to supply: Tools you will need:

The LED

The LED has 2 legs, the longer one is positive, the other is negative. What if you cut the legs the same length and forget which is which? The LED also has a flat side on the plastic part, that is the negative side and must be hooked to the negative wire coming from the battery.

The Resistor

The resistor is used to regulate the voltage. If you apply too much voltage to your LED, the LED will glow as bright as the sun (and blind you temporarily, I've done it) then burn out without so much as a wimper. Resistors are valued in watts and ohms. Use a 1/4 watt resistor. Here's how you calculate the right ohm value:

(total_volts minus volts_used)/amps_used

So the total volts we have is 9v from our power supply (battery). The LEDs each use 3.5v, for a total of 7v. (You add volts together for all LEDs.) The amps used by the LED is .02 (aka 20 milliamps). (Do NOT add amps together for all LEDs.)

So our equation is: (9v-7v)/.02 = 2/.02 = 100 ohms.

If your supplier does not carry the exact ohms (lets say you calcualted 96 ohms) go up to the next resistor size, i.e. 100 ohms.

Cut out holes in your project box

Use a drill and/or Dremel to cut holes in the project box. For the rectangular switch, trace the smaller part of the switch onto your box and cut with a Dremel. The switch should have snaps that allow it to snap and hold in place. Use a 5mm drill bit for the LEDs.

When done, file or sand any rough edges in the metal.

Connecting it together

Here's where you connect the parts together. See the schematic picture below. You should solder all connections to make a good solid connection. I believe my actual photo is different from the schematic. The resistor is attached between the switch and the right (bottom) LED.

  1. First, install the LEDs into the 2 holes with epoxy. When it dries it will make it easier because the case will hold the LEDs in place while you solder other parts. It might take 4-8 hours before you can work with the LEDs again.
  2. Now, preheat your soldering iron.
  3. Solder the positive and negative wires of the 2 LEDs. A plus wire should connect to a negative wire. Twist the 2 wires together then solder. Do not get the LEDs too hot or they will fail. Instead, drip the solder onto the connection.
  4. Next, solder the resistor to the negative leg of the left LED. It does not really matter where the resistor goes, but since the switch is on the right, to balance things I put the resistor on the left side of the circuit.
  5. Now solder the other leg of the resistor to the minus wire of the 9v battery clip. The negative wire is usually the black wire, the positive is usually the red wire.
  6. The switch is a little tricky because they often have 2 columns of 3 metal legs. That's why I saved this for last.
    1. Connect your battery to the 9v clip.
    2. Press the switch so it is on.
    3. Hold the switch in your hand so there are 2 vertical columns of 3 legs each. (See image above.)
    4. Now take the positive wire of the 9v clip, and press it against the bottom leg of the left column. Take the other leg of the right LED, and press it against the bottom leg of the right column. Basically, one column is for one wire, the other column of legs is for the other wire.
    5. If the LEDs light, solder the wires to those legs.
    6. If the LEDs do not light, try touching the wires to different legs. If that doesn't work, try the middle row of 2 switch legs.
You're done! Test the light. Turn the switch off and on. You can now drill a hole in the back of the case for mounting on a nail for hanging on the wall. Or drill 2 holes in the side of the case, add a string and hang around your neck to read a book. Partially open the case and set the light on a table pointing up for an area light.

If you like this project, let me know at chuckr 44 -at- gawab dot com. Remove any spaces and dashes.

Links to LED light projects: