The post explains the construction of a homemade 10 watt LED lamp using ready made 12 V SMPS adapter. The project was successfully built by Mr. Debabrata Mandal.
In many of previous posts I have discussed the use of 1 watt white LEDs for making high efficiency LED lamps for implementing in homes for high bright, low consumption illumination.
LED Tube without PCB
Here we learn yet another interesting high watt LED lamp project which was constructed by Mr. Debabrata, using 12nos of high bright 1 watt LEDs fitted over a steel plate.
An ordinary $2 12V/1amp SMPS power supply was used for driving it. Remember I have already discussed the construction of this SMPS circuit in one my previous posts?
However in the proposed 10 watt LED circuit there are a few serious technical flaws which needs to be rectified for ensuring long life to the lamp and for obtaining optimal results from the unit.
The first issue could be with the use of steel material as the heasink. As we all know that steel is not an efficient conductor of heat, therefore it's definitely not recommended as a heatsink especially for LEDs which are highly sensitive and vulnerable to heat and current.
The rise in temperature within these LEDs could result in forcing the devices to suck more current which could eventually get transformed into a run away situation and permanent damage to the LEDs or weakening of their illumination.
The following response from Mr. Debabrata simply highlights the above issue.
Bro, these 1w LEDs produce GINORMOUS amount of heat.... daaaaamn with 12x1w... this steel plate aint dissipating enough. The plate area behind the led bunch is getting so hot tat those plastic glue is semi-melting & also heating up the smps board stuck behind
Can u tell me where i can get 1 foot aluminium strip? Kinda like a ‘scale/ruler’... so i can arrange the LEDs like a tube? ....wider light & more heat dissipation
Using Aluminum Heatsink Base instead of Steel
The above issue can be easily tackled by incorporating an aluminum plate instead of steel or iron. Size could be a matter of trial and error, it's always better to go for a much larger aluminum surface relative to the LED assembly dimension. Also make sure the plate is not thicker than 1mm, in fact the thinner the better, but not less than 0.5mm.
The above solution will definitely take care of the heat dissipation of the LEDs, however if the ambient temperature gets warmer, as we commonly experience in tropical countries during summer time, the above solution might not be enough and could start causing problems.
For this a simple yet effective solution is to incorporate a current limiter circuit in between the LED board and the SMP supply. This will restrict the LEds from drawing current beyond the set safe limit irrespective of the ambient temperature levelconditions.
I have already covered a very useful current limiter design in one y previous posts, so we can incorporate the same for the present design.
In the prototype images shown below we see that the LEDs are arranged in group of 4s, and the power supply used is 12V. As per the standard formula the arrangement will not require individual resistors, however since each LED would be getting only 12/4 = 3V,the illumination could get slightly lesser, because for optimal power a 3.3V is recommended for these LEDs.
You can again refer to the circuit and the formula presented in the above mentioned LED current controller circuit which shows a configuration using 3 LEDs in the series with individual limiting resistor.
The resistors perform the function of distributing the current equally to the individual strings so that the illumination is uniformly emitted across all the LEDs.
Here's a more comprehensive circuit which shows the correct method of employing high bright 1 watt LEDs for making 10 watt or higher wattage LED lamps for home decor and lighting: