Crystals glow
Quite often people have to buy 1W and 3W LEDs. If we do this in trusted stores, then there is no big problem. And if we do this at new sites? How not to be deceived? How to distinguish 1W LED from 3W LED? In principle, the task is not impossible ... Let's see and try ...
What are powerful 3 W and 1 W LEDs I will not disassemble. If you are reading this material, then it seems to me that you understand quite well what and what. For what and for what purpose they bought.
Comparison of two 1W and 3W LEDs
Features 1W LED
We see that the operating current of 1 W of the diode is 350mA, 3W is 700mA. The maximum peak current for both is 0.8 A. both of these diodes will operate at the maximum possible 0.75A. They will work at 1 A, but not for long). You shouldn't overclock the chips unnecessarily, we are still concerned about their durability. Moreover, if you have purchased the correct LED, then the brightness will be enough for you.
How to distinguish between 3W and 1W LEDs
When you turn on the chips at full power, you can hardly tell the difference between 1W and 3W by light. The eye will not perceive too bright a glow.
You can use a black box, individually turn on the LEDs and see which sample will give the most light effect. Instead of a box, you can use a black sheet. This is an example, but the meaning is clear, I think. 
If you have two diodes of not clear origin, then you can determine which of them is 3 W and which 1 W can be done in the following way: we connect both to a power source and supply 3.5 V to them. In this case, the initial value of the current should be within 350mA. Let's look at the graphical dependence of brightness on current.
Dependences of 1 and 3 W LEDs on current
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Graph of dependence of 1 W diode
Graph of 3 W diode
With an increase in the initial voltage of 3.5 V, the brightness of 1 W of the diode will increase slightly and practically stop if the voltage (current) is further increased. If you have a 3 W diode, then with an increase in voltage from 3.5 V, the current will increase, and according to the graph above, we see that the brightness will gradually increase until the current reaches 700 mA.
Graph of current versus voltage for 1 and 3 W LEDs
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Current versus voltage 1 W
The dependence of the current on the voltage of a 3 W diode
Those. visually, we can identify any 1 W or 3 W LED if by applying a current of 350 mA to it, we will gradually increase it. An increase in brightness from 350 mA indicates that we have a 3 W diode in front of us. A slight increase in brightness from 350 to 700 mA indicates that we have a 1 W diode in front of us.
Another way to determine where a 3W or 1W high power LED is is heating. It's simple physics here. At the same 350mA 1W, the LED will heat up quickly. And you cannot hold it in your hand. A 3 W LED at the same current can be held in the hand for a long time without noticeable discomfort. Naturally, this is a side way of determining where which diode is. But it has a right to exist.
Well, the last way is to distinguish LEDs by crystal size. To be sure to do this, you should purchase a USB microscope. This is a budget option and is of sufficient quality, with the necessary gadgets. you can see many microscopes of various price categories. In general, the USB microscope is an interesting contraption and will come in handy at home more than once. Further, using a calibration ruler and a pre-installed program, you can easily measure the dimensions of the crystal. With it, we can say exactly what size of the crystal is set. However, this method will not give us an exact idea of where which diode is. But taking into account that the larger the crystal, the more power - accordingly, you can draw a conclusion for yourself.
Powerful 1W diodes have dimensions of 30x30mil. Crystals in 3W diodes - 45x45mil. These are, of course, ideal sizes.
If you do not have a microscope, but want to know the dimensions, then you can use the tools at hand. Let's apply a very small current to the LEDs. Crystals will start to glow faintly.
Crystals glow On the left, we see that the crystal size is an order of magnitude larger. This particular LED was purchased from Aliexpress. The sample that was purchased in an off-line store is clearly 1 W, despite the fact that it was sold with a declared power of 3 W. In principle, one glance at the crystal through a microscope was enough for me to understand where the diode will be. But for myself, my beloved, I checked the glow by the first method (increasing the current) and the visual conclusion was confirmed.
So that is all. In such simple ways, now you can safely check, compare and distinguish between 3 W powerful LEDs from 1 Watt. But, in order not to do this constantly, it is worth purchasing LED products in proven stores and sites.
Crystal measurement video to distinguish 1 and 3 W LEDs
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