How to Build a LED Flashlight

They exist in the market powerful LED flashlights (+ 10W), but its price makes them inaccessible to most mortals; in this entry we will use our imagination to build us a powerful and efficient LED flashlight for less than € 15.

We will only need LED, a sink of computer, a battery (optional) and a switch to have a basic but useful flashlight.

Materials and tools

  • Aluminum heat sink or similar large computer; how much more power have LED larger you need to be. We can also put one small, but then to maintain a “healthy” temperature for LEDs, we will have to connect you with a fan.
  • Dremel or rotalin small to cut small materials with the necessary Individual protection (glasses, gloves, etc.).
  • Scissors.
  • Welder ‘s minimum 20W.
  • LED of the power that we need; in this case use 10W which gives about 900 lumens, more than enough.
  • Controller (optional if the battery supply lower voltage to which works LED). If we can prevent their use, as well as get out cheaper, the battery will last us a little more.
  • Battery holder (optional if we combine batteries with welded wire), is recommended if we can not directly charge flashlight batteries and you have to put them in a magazine. In this case I recommend using one to 3 Li-Ion 18650 batteries.
  • Worth somebody, batteries, rechargeable, conventional, lithium, NI-MH… but the best practice is to use lithium ion batteries 18650 like these but with protection; they are the most economic, resistant, durable and suitable for an LED flashlight (as they are downloaded very little if they are not used), with circuit protection possible. In this case we will obtain 11, 1V using 3 batteries in series (in an led voltage and intensity are related; if low voltage below the nominal led, also reduces your consumption, and we avoid to control the intensity or amperage).

Parts needed

To produce you can use rechargeable batteries or not, just need together them in series to get a volt less which LED calls to avoid putting a resistor or controller to regulate the current (current in amperes).

First warn you that, although this experiment used voltages low and safe for people, in the case of a lithium ion battery short this may overheat much and explode in a dangerous way. I do not become responsible for the bad use of these indications.

To put them in series their voltages are added (3, 7V + 3, 7V + 3, 7V = 11, 1V, see for details.). If we choose to solder wires to batteries, we have to use a soldering iron 40W minimum, scratching or sanding each one of the poles and tinning flux with solder, by heating the metal well and applying the Tin until it is attached, carefully not to overheat the battery.

We combine positive to negative in a zig-zag to put them in series

However, I recommend using a battery holder as follows (available for the 18650):

Note: is not the same voltage (voltage) that power or intensity (measured in amperes). To give you an analogy, electrons pass through a cable is like drops of water in a pipe. The voltage is as the width of the pipe, and the amp is the number of electrons (or drops) that go over the line.

Power (W) = voltage (v) x current (A)

Or if we return to the formula; Intensity (A) = power (W) / voltage (v)

For example, in this case I’m using a 12V LED that consumes Max 10W (consumes 10/12 = 0, 83 amp at full power), but to extend its useful life are going to manage less voltage (with what will also reduce the AMPS).

The longevity of an LED only depends on two factors (apart from their quality): the temperature to which it is subject, and the intensity of the current circulating it; i.e. the more lights and more temperature (above 60 ° C is harmful), less time will last.

Then we can paste the LED to the sink; I have used glue epoxy two-component (that holds temperatures well below 80 ° C) to paste it, and with a pair of pliers subject in place until the glue hardens. Best is to use glue for coolers, a white paste that conducts heat, which hardens as the adhesive quite well.

This is very simple and gives good result (when more glued the aluminum led, better), but If you’re pretty clever you can make holes in the sink, screw them and fasten the screw led to the sink (power LEDs come with holes and forms prepared for this purpose).

It is essential that led with the heatsink contact is as perfect as possible; both surfaces must be free of impurities and the more smooth and United as possible.

With a pair of pliers we hold led to sink until the glue to harden

To do a test I have connected the battery to the switch, and I lit led a few seconds; Note the amount of light emitted, enough to light up a room or as in this case, through the part of orange plastic clip.

Note the amount of light that emits this 10W led

Warning: do not look directly at the LED when lit; the high power can damage eye (retina) even more than looking directly at the Sun (is suitable to be placed on a white light diffuser in a way that is not directly).

If we want to limit the current to 6W and be able to use any battery between 8v and 25V AC/DC, we can use this simple controller (controller or driver), used in the bulbs of 12V LED, which limits the current to 620 mA:

This transformer 12V 350mA current regulate us (have I desoldering skewers)

Image controller has an input through skewers (is a driver for MR16 bulbs), which can remove to weld the input, and output weld positive to positive and negative to the negative of the led and led, as shown in the picture below:

Detail of the connection with the switch

Now just need to package it all; You can use a plastic, carton box, or whatever you want, provided that sink is exposed to the air so that it is cool. The simplest is to make a block with duct tape:

Prepared homemade flashlight

And we already have a lantern walk through the House when necessary.

Note: high power LEDs is that we can regulate the light managing less voltage; If you’re a handyman of electronics you can use a potentiometer and controller to handle the intensity.

Also we can build us a LED lamp using a chip right led and its controller, but that already be explained in another entry…

Final tips

  • Get a LED that works to more voltage that the battery to avoid unnecessary energy expenditure with a resistor (which should be placed to adjust the intensity (amp) if we want to work with the nominal voltage).
  • Sure to turn it on for 5 minutes which is not heated too neither sink nor batteries, if you can not touch it with your hand, then is that or either do not have a sink suitable for high-power LED or we are forcing you too, with which shorten their life dramatically.
  • You don’t feed the LED with more voltage or intensity of the recommended by the manufacturer, much shorten the life of the LED.


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