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!
Step 1: Materials and Tools
- 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.
- Soldering iron with solder
- Helping hands (helpful but not needed)
- Hot glue gun with glue
- Wire cutter/stripper
Once you have everything gathered, lets move on!
Step 2: Populate the Board
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
Step 4: Add the Connector to the Board
Step 5: Test What You Have So Far!
Step 6: Build the Flashlight
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
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
Step 9: Conclusion and How to Use
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!