It's been almost a year since I started replacing all the lamps in the house with LED ones. The results were sometimes more pleasing, sometimes less, but one incident led me to an interesting decision.
The reason why I took up the LED lamp
Have you or someone in your family accidentally knocked over a table lamp? If we talk about me, then quite a few times... Therefore, when my child once again dropped my table lamp with an innocent “Oh!”, I said: “That’s enough!”
Warning! Fluorescent lamps use mercury, which is highly toxic.
If you accidentally or intentionally break such a lamp, it is recommended to ventilate the room well to rid it of toxic fumes.
I decided to replace the fluorescent tube on my table lamp with something more shock resistant...
My light needs to be able to withstand the handling of a 10-year-old child, yet produce enough light to comfortably work at a desk, operate consistently, and be inexpensive.A couple of years ago, this problem did not have a simple solution, but now the answer is obvious - it is an LED lamp.
Materials
I decided to use Cree MX6 Q5 LEDs with a maximum luminous flux of 278 lm, which I still had from the last project. Light-emitting diode will be placed on a cooling radiator measuring 5 x 5 cm, which was removed from an old PC.
For simplicity, I decided to use a pulse phone charger that will provide enough voltage and current to run the LED lamp. For this purpose, I used a non-working Siemens A52 charger, with a stated voltage output of 5 V and a current of 420 mA.
The old fluorescent lamp socket will serve to protect the electronics.
Measurements
According to the factory specifications, the Cree MX6 Q5 can be powered from a maximum current of 1 A and a voltage of 4.1 V. I figured that I would need a 1 ohm resistor to reduce the voltage by 1 V (from the 5 V that the power supply provided ) up to 4.1 V consumed by the LED, if only the power supply can withstand a current of 1 A.
To check the maximum permissible current that the power supply will withstand, I connected various resistors to its terminals, in each case measuring the voltage and calculating the current.
I was surprised to find that the power supply is designed to limit the current to 0.6A, which it can handle just fine. Having done similar research with other phone chargers, I learned that they all have a current limit of 20% to 50% higher than what the manufacturer claims.This makes sense, since every manufacturer designs the power supply in such a way that it will not get very hot, even if the device being powered is broken, including from a short circuit. And the easiest way to ensure this is to limit the current.
So I had a DC generator with current limitation to 0.6 A, very efficient (the mobile phone power supply does not get very hot during use), powered directly from a 220 V AC source, factory made and very small in size . And it's just wonderful.
Making a lamp
First, I disassembled the power supply to remove the internals and insert them into the new lamp. Since most power supplies are glued together during assembly, I used a hacksaw blade to open it.
Some adjustments needed to be made to ensure the board would fit into the lamp socket.
To secure the board inside the socket, I used silicone sealant, which remains highly resistant at high temperatures. Before closing the base, I attached a heat sink to its cover (using a screw), on which it was fixed Light-emitting diode.
Result: table lamp
Here is the assembled lamp. Energy consumption does not exceed 2.5 W, and the illumination is 190 lm, ideal for an economical and reliable table lamp. And all this in an hour of work, with the exception of the hardening of the silicone sealant and the drying of the hot-melt adhesive that was used for fixing LED on the cooling radiator.
I was so inspired by the success and simplicity of the project that a few hours later, I already had another lamp.
Result: hallway
Impressed by the results, I proceeded to replace several fluorescent lamps in my apartment in the same way. I will present them, going into only a few details.
For the hallway light, I used two Cree MX6 Q5 elements with an energy consumption of 3 W and a maximum luminous flux of 278 lm. Each is powered by an old Samsung cell phone charger. Despite the fact that the manufacturer claims a current of 0.7 A, I found through measurements that the limit is set to 0.75 A.
Everything is secured with textile fasteners (Velcro), glue and plastic mounts for the motherboard.
The total energy consumption of the structure is 6 W with a luminous flux of 460 lm.
Result: bathroom
For the bathroom I made a light from a Cree XM-L T6 that was powered by two LG cell phone chargers. According to the factory specifications it can produce 0.9A of current, but in practice I found it to be limited to 1A. The two units are connected in parallel for a total current of 2A.
Such a lamp will consume 6 W of energy and provide illumination of 700 lm.
Result: kitchen
If in the case of the hallway and bathroom, providing minimal lighting was not too significant, then the kitchen is a different story. I didn't want my wife or anyone else to cut their finger while cooking and blame it on me, or worse, my darling LED lights...
To provide good lighting for the kitchen, I decided to use not one, but two Cree XM-L T6 elements, each consuming 9 Watts and producing 910 lumens.As a heat sink element, I used a cooling radiator from a Pentium III microprocessor, onto which I attached two LED.
Although the Cree XM-L T6 can operate at a maximum current of 3 A, the manufacturer recommends using 2 A for stable operation, at which Light-emitting diode will emit about 700 lumens. Testing several power supplies showed that they were either not limited in current, or the limit was greater than the required 2 A. I was able to find a power supply that, based on the technical specifications, produces 12 V at a current of 1.5 A. After testing with resistors, it turned out that the current is limited to 1.8 A, which is very close to the desired 2 A. Excellent!
To provide insulation for the heatsink and the two LEDs, I used two neodymium magnets from a non-working DVD drive and plastic motherboard brackets. Everything is fixed with glue and Velcro.
Although I expected this lamp to produce 1300 lumens of light output, similar to the 23 W fluorescent lamp it replaced, I was pleasantly surprised to find that the light produced by the new lamp was noticeably brighter, and the power consumption was 12 W - almost half as much.
Conclusion
The coolest part of this project is that it can be done using items that, with the exception of LEDs, almost everyone has on hand.
Thus, you can get an LED lamp at a price that is half or even four times lower than the cost of an LED lamp in a store.
I hope that now old mobile phone chargers will be useful again and not end up in the bin.
Thank you for your attention!
Original article in English
