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The Ultimate Household/Emergency Flashlight System

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This flashlight and base work together to create the ultimate household flashlight system! The base makes a soothing night-light, keeps the flashlight charged, and will turn on a high-brightness LED if a power outage strikes. When the flashlight is removed from the base, it becomes a super-bright lantern to help you find your way, and will also work as a battery powered desk lamp.

Even though it is designed to help in a power outage, it also works as a perfect around-the-house flashlight. It is especially useful that you can set it down and bend the light to wherever you need it, and keeps your hands free. The base makes recharging easy and leaves the flashlight always ready to use, no need to mess with batteries.

It's also cheap and very easy to make!

How it works:

A wall-wart transformer is constantly plugged in and connected to the base. A PNP transistor has its base connected to the power in from the wall, and the voltage from that turns the transistor off. When it stops getting external power, the transistor is turned on and sends power through a connector to the flashlight. This turns on the flashlight's high power LED on a low power, letting out plenty of light to find your way but conserving the batteries. If the button on the flashlight is pressed, it goes to full power.


Now let's get started!
 
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Step 1: Materials and Tools

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Here is what you should have to build this project:

Materials:
  • Small piece of prototyping board.
  • Wall-wart transformer with a voltage of at least 7.5v. Low current is fine but you might want more (500ma) if you will be running the flashlight at full power while it is connected to the base.
  • 4x AA rechargeable batteries (I used Energizer 2450mah)
  • 4AA battery holder.
  • Small heat sink for LED with heat sink grease.
  • Insulated wire, for the board and for the flashlight.
  • Think, solid wire to support the bendable neck of the flashlight.
  • A small connector set with at least three wires, this hooks the flashlight to the base.
  • Small zip tie, I needed one for the wall wart but you might not.
  • Milk carton; I cut a piece off to cover the base and diffuse the night-light LEDs.
  • Q1: LM317T adjustable voltage regulator.
  • Q2: A PNP transistor. I used a TIP42
  • D1: Pretty much any diode (not zener). I used a 1A 400v rectifier diode.
  • S1: A small PCB mountable switch. You could use a large, non-PCB mountable one if you attach wires to it, it's just not as pretty.
  • S2: A larger, non PCP mountable push-on push-off button. You could use a small, PCB mountable one, but it will be harder to use and might not be able to handle the current.
  • R1: For your LED(s). Will vary with what LED(s) you use, I used a 10 ohm 10 watt. If you have the right parts (I didn't), it is recommended you build something like this.
  • R2: 1k ohm resistor, for the transistor.
  • R3: 10k ohm resistor, for the transistor. If you want to have the light come on brighter when the power goes out, lower the value of this resistor.
  • R4 and R5: will vary with what LEDs you use for the night-light. Mine were 82 ohm.
  • R6: 560 ohm resistor, for the regulator.
  • R7: 2.2k ohm resistor, for the regulator. In combination with R6, they make the regulator output around 6 volts.
  • LED1: The high-power LED in the flashlight. You could use a bunch of normal ones if you wanted to, just make sure to use the proper resistors.
  • LEDs 2-5: The four LEDs for the night-light on the base.
That may seem like a lot, but it really isn't that much.

Tools:
  • Soldering iron with solder
  • Helping hands (helpful but not needed)
  • Hot glue gun with glue
  • Wire cutter/stripper
  • Scissors
  • Pliers

Once you have everything gathered, lets move on!

Step 2: Populate the Board

Your layout might be different than mine so you can base your layout on the schematic. If you are following mine, there are tons of pictures to follow! Rather than include a giant block of text, read the mouseover text on each of the yellow boxes on the pictures.

First add all of the components, and then add wire jumpers to connect far places of the board.

Sorry about the pictures, a lot of them came out blurry even though I did multiple takes and picked the best ones. I don't have a good camera or lens for close-ups.

Step 3: Connect the Transformer

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Cut the end off your transformer and strip the wires. Solder the positive wire to pin 1 (Vin) of the regulator and the ground to a common ground. Hot glue it to the board so it doesn't get ripped out by accident, and add a zip tie for support.

Step 4: Add the Connector to the Board

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Attach the connector for the flashlight to the board. Pin one goes to ground, pin two goes to the cathode of the diode, and pin three goes to the collector of the transistor. Hot glue the connector to the board for support, unless you connector is the kind that can hang loose.

Step 5: Test What You Have so Far!

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Turn the LED switch on and plug in the transformer; the LEDs should come on. If you flick the switch, they should turn off. If none of this happens, you need to go back and troubleshoot. If it works, continue!

Step 6: Build the Flashlight

This could easily be about 20 steps, but it would much more convenient for both of us if it was one step with a lot of pictures that have mouseover text.

Don't bother reading the following if you are looking at the pictures; it is the same thing as the mouseover description.

Cut a piece of the thick wire at least 30 cm long (if it's too long you can cut it later). Bend it in half where the center is and fold it back along itself. Bend the part where you folded it into a squiggly pattern that forms a flat area. This will be glued onto a flat surface.

Find your non-PCB-mountable switch and glue it on its side on top of the battery pack. solder the ground wire of the battery pack to one of the terminals.

Take your resistor (or high power LED driver circuit if you built one, which is recommended for efficiency) and glue it along the side of the battery back. Bend one of its wires to the other terminal of the switch and solder it there.

Cut a piece of insulated wire at least 25cm long. Strip one end and solder it to the other wire of the resistor, which can be cut short.

Fold the wire over the switch to the part of the battery pack next to the switch. Twist the wire into a loop over half of the remaining surface area, and fold the end upward.

Lift loop up, apply a blob of hot glue, and press the loop down. Hold it in place until the glue cools.

Cut another length of insulated wire at least 12cm long, strip one end, and solder one end to the positive wire of the battery pack.

Find your LED and the small heat sink. Apply a very small amount of heat sink grease to the heat sink and press the LED down on top.

Pick up the twisted thick wire thing we made earlier and stick the two ends through parts of the heat sink. Cut off enough wire so that you can stand the end of the wire on the end of the battery pack and still have the wires reach the LED. Hot glue the wire to the heatsink in multiple places, and hot glue the edges of the LED to the heat sink.

Apply a large blob of hot glue to the remaining surface at of the top of the battery pack. Push the twisted end of the LED support wire into it, and wait for it to cool. Then, grip the LED end with pliers and twist it until it looks like the picture.

Solder three wires from the connector as follows: one to the positive battery holder wire, one to the negative battery holder wire, and another to the terminal of the switch where the resistor is. In the picture the colors (in order) I used for these were red, black, yellow. The blue wire was not used. Glue the connector along the side of the battery pack so the plug is at the bottom.

Lastly, wrap the two LED wires around the LED's stalk and solder them to their corresponding terminals.

Step 7: Test the Flashlight

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First, charge the batteries using a normal charger, then put them in the flashlight and push the button. If it turns on, yay! Push it again to turn it off. If it doesn't work, check it with a multimeter and/or look over the connections. Is the LED in backwards?

Now, plug the flashlight into the base, making sure you put the connector in the right way. The LED on the flashlight should come on (dimmer than normal, that was intended to save battery for when the power goes out) because the base is unplugged. Plug in the base and it should turn off. Yay, everything should be working! If this doesn't work but the flashlight does, compare your board against the schematic.

Step 8: Light Diffusion

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Normal LEDs are very directional, which makes a bad night-light. Diffusing the light will make it radiate out more evenly and light up the area where it is located. Take a milk jug and cut out the part that has the circular depression in it. It should fit over the board perfectly. Apply a small dot of hot glue on each of the four LEDs (the glue helps diffuse the light) and press the cover on top.

Step 9: Conclusion and How to Use

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Congrats, your done!

To use your awesome flashlight/night-light/emergency light/work area light, you want to keep it plugged in all the time. It might sound inefficient, but the entire system uses less than one third the power of a normal night-light (tested using a kill-a-watt). An uninterruptible power supply for a computer is way more inefficient and serves a similar purpose. By keeping it plugged in all the time, not only are you keeping the batteries charged, but when the power goes out on a dark night the light will come on to help you find your way.

Some people may want a cover or case on theirs, but I like how it looks more DIY.

I hope you found this Instructable very helpful. If you build this, please send pictures!

Please rate and comment, I like comments :-)

Contest: This Instructable is entered in the flashlight contest. I'm not telling you to vote for me, just to vote for who you think should win. Remember, you can vote for as many entries as you want to!


batman963 years ago
Could you post a schematic that uses normal batteries, and just uses the wall wart power to sense the presence of power, and to run the light if you want to switch it on when the power is on, I was thinking about using something like this with regular batteries for our wireless telephone base, when the power goes out it would switch to the batteries, like a mini UPS for computers, could you post a schematic?

Batman96
dark sponge (author)  batman963 years ago
For that you can probably take out the voltage regulator, the resistors and diode connected to it, and the middle pin of the connector out and it should work. I'd like to see it if you make it, good luck!
Thanks, I will try it when I get a few other pressing projects done.

acoleman34 years ago
funny how some of these components look like they came from thecustomsabershop.com. especially the rebel star LED and the PCB. nice idea to have these plans available.
no actually....it looks like most of the SEOUL P4 LED blade kit now that i think about it. the switch looks like its from radio shack since teh kit only has a momentary switch.
dark sponge (author)  acoleman34 years ago
I got the LED (and pretty much everything else) from Mouser, I could look up the model number if you want. But you're right, the switch is leftover from the days when I would still shop at Radioshack :-)
hg3415 years ago
love how the chargeing base is a night light you need to work on a case
dark sponge (author)  hg3415 years ago
Thanks! Personally I don't think it needs a case, but I'm sure a lot of people would. If you make one, please send pictures!