There are on the market powerful LED torches (+10W), but their price makes them inaccessible to most people; in this post we will use our imagination to build a powerful and energy efficient LED torch for less than 15€.
We only need the LED, a computer heatsink, a battery holder (optional) and a switch to have a basic but useful torch.
Materials and tools
- Heatsink The more power the LED has, the bigger it will have to be. We can also put a small one, but then to maintain a "healthy" temperature for the LED, we will have to attach a fan to it.
- Dremel or small rotary cutter for cutting small materials with the necessary Personal Protective Equipment (goggles, gloves, etc.).
- Welder 20W minimum.
- LED of the power we need; in this case it uses 10W which gives about 900 lumens, more than enough.
- Regulator (optional if the battery supplies a lower voltage than the LED works). If we can avoid using them, the battery will not only be cheaper, but it will also last a little longer.
- Battery holder (optional if we join the batteries with soldered cables), it is recommended if we can't charge directly the batteries of the lantern and we have to put them in a charger. In this case I recommend using one for 3 Li-Ion 18650 batteries.
- BatteriesAny rechargeable, rechargeable, conventional, lithium, NI-MH... is suitable, but the most recommended is to use lithium-ion batteries 18650 batteries like these but with protection; they are the most economical, resistant, durable and convenient for a LED torch (as they discharge very little if they are not used), with protection circuit if possible. In this case we will obtain 11,1V using 3 batteries in series (in a LED voltage and intensity are related; if you lower the voltage below the nominal voltage of the LED, its consumption also decreases, and we avoid controlling the intensity or amperage).
Rechargeable batteries can be used to manufacture it or not, we just need to connect them in series until we get a few volts less than the LED asks for to avoid putting a resistor or controller to regulate the current (intensity in Amps).
First of all, please note thatThe experiment uses low, human-safe voltages, although this experiment uses low, human-safe voltages, in the event of a short-circuit of a lithium-ion battery, the battery can overheat a lot and to explode in a dangerous way. I am not responsible for any misuse of these instructions.
When put in series their voltages add up (3.7V+3.7V+3.7V+3.7V=11.1V). If we choose to solder the cables to the batteries, we have to use a 40W soldering iron minimum, scraping or sanding each of the poles and tinning with tin with flux.The metal should be heated thoroughly and the tin applied until it bonds, taking care not to overheat the pile.We join positives to negatives in zig-zag to put them in series.
However, I recommend using a battery holder as the following (available for 18650):
Note: Voltage (voltage) is not the same as current or intensity. (measured in amperes). To give you a simile, the passage of electrons through a wire is like the passage of water droplets through a pipe. The voltage is like the width of the pipe, and the amperes is the amount of electrons (or drops) flowing through the pipe.
Power(W) = Voltage(v) x Current (A)
Or if we turn the formula on its head; Current (A) = Power(W) / Voltage(v)
For example, in this case I am using a 12V LED that consumes 10W maximum (it consumes 10/12=0.83 Amps at full power), but to extend its life we are going to administer less voltage (so we will also reduce the amps).
The longevity of an LED depends on only two factors (apart from its quality): The temperature to which it is subject, and the current intensity that circulates it, i.e. the more it illuminates and the higher the temperature it reaches (above 60°C is harmful), the shorter it will last.
The following we can glue the LED to the heatsinkI have used two-component epoxy glue (which withstands temperatures below 80ºC) to glue it, and with a clamp I hold it in place until the glue hardens. The best is to use heatsink glue, a white paste that conducts heat quite well, which hardens like glue.
This is the simplest way and gives a good result (the more the LED is glued to the aluminium, the better), but if you are skilled enough you can drill holes in the heatsink, screw them in and attach the screwed LED. to the heatsink (power LEDs come with holes and shapes prepared for this).
It is essential that the contact between the LED and the heatsink is as perfect as possible.Both surfaces must be free of impurities and as smooth and even as possible.
For testing purposes I connected the batteries to the switch.I have illuminated the LED for a few seconds; note the amount of light it emits, enough to illuminate a room or, as in this case, to pass through the orange plastic part of the clamp.
Warning: Do not look directly at the LED when switched on; high-powered ones can damage the eyesight (retina) even more than looking directly at the sun (it is advisable to place a white light diffuser over it so that it is not directly visible).
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 regulator (controller or driver), used in 12V LED bulbs, which limits the current to 620 mA:
The controller in the picture has an input via spikes. (it is a driver for MR16 bulbs), that we can remove to solder the input, and in the output we can solder the positive pole to the positive of the LED and the negative pole to the negative of the LED, as shown in the following image:
Ya all that's left to do is to pack it all upWe can use a plastic box, a cardboard box, or whatever we want, as long as the heatsink is exposed to the air for cooling. The easiest way is to make a block with insulating tape:
And we already have a torch for when we need it.
Note: The good thing about high-power LEDs is that we can dim the light by managing less voltage.If you are handy with electronics, you can use a potentiometer and the dimmer to control the intensity.
Also we can build ourselves an LED lamp using a suitable LED chip and its driver.but we'll explain that in another post...
- Get an LED that works at a higher voltage than the battery. to avoid unnecessary energy expenditure with a resistor (which would have to be placed to regulate the current (amperes) if we want to work with the nominal voltage).
- Check that it does not get too hot when switched on for 5 minutes. If you can't touch it with your hand, then either it doesn't have an adequate heatsink for the power of the LED or you're pushing it too hard, shortening its life drastically.
- Do not supply the LED with more voltage or current than recommended. by the manufacturer, you will greatly shorten the life of the LED.
More information - How an LED works