- Consumer Electronics & Personal Gadgets
How to Use 1 Watt LEDs
This is how a 1 watt white LED looks like
Understanding a 1 Watt White LED
We all probably know what LEDs are as they are being used in almost every electrical gadgets nowadays.
Precisely these are electronic components which are able to generate outstanding illuminations with relatively lower electricity consumption.
LEDs come in all shapes, sizes and specs which offer the user a wide range of choice for their specific applications.
1 watt white LEDs are probably the most popular ones today since these types are highly advance and are capable of generating intense lights with minimum consumption.
Understanding a 1 watt white LED operating parameters is pretty simple, unless you are one those who doesn't know anything about electricity, and have never come across LEDs.
Technically a 1 watt white LED is very similar to an ordinary 5mm LED which we normally witness in equipment such as TV sets, DVD players, music systems etc.
The only difference between an ordinary LED and a 1 watt LED is the current (Ampere) spec.
An ordinary 5mm or 3mm LED would normally require currents around 10 to 30 mA, whereas a 1 watt white LED needs somewhere around 300 mA.
However as far as the voltage is concerned, it's mostly fixed at around 3.3V for all of them.
Therefore basically a 1 watt white LED requires 3.3 volts at around 300mA current for producing highly intense white light beam. This light beam may be so intense that looking directly into it for long could permanently damage your eyes or at least make you partially blind, so never look at them straight on.
How to Use a 1 Watt White LED
Due to its high lumen per watt efficacy, a 1 watt white LED becomes specifically useful for lighting home and office interiors, and also in appliances such as emergency lights, flashlights, solar lanterns etc.
Wiring a 1 watt white LED is so easy that even a layman would be able to implement it within minutes.
As shown in the image above, a 1 watt LED has two terminals: a positive and a negative.
It's all about connecting these terminals with correct polarity to a 3.3V DC source. This DC source should be rated at around 1 amp for optimal brightness of the LED.
The voltage is actually not a fixed parameter, it may be anywhere from 3V to 3.5V, but should never exceed the 3.5V mark.
The DC source can be obtained from a standard 3V/1 amp SMPS adapter unit, a 3V/1AH battery, or may be from a home built transformer power supply.
However there's one thing that must be taken care of while using a 1 watt white LED: the current should never exceed 350mA, or in other words a long as the supply voltage is maintained below 3.5V, your device would be safe (within 350mA).
Therefore it implies, the DC source which is being used should have a built-in voltage regulator so that a constant voltage within 3.5V is ensured.
But actually there's nothing to worry in case you have a power supply source which is crude, not regulated, and has a voltage that's far above the 3.3V limit, in that case you may simply employ a suitably calculated resistor in series with the LED.
Calculating the Correct 1 Watt LED Limiting Resistor
As discussed in the previous section, in case the DC source voltage is a mismatch and high above the required 3.3V mark, a resistor can be employed in series with the LED for operating it safely and also acquiring optimal brightness.
Suppose the power supply voltage is 12V, the following formula would provide you with the exact resistor value required for the application.
R = (U - Fwd.LED)/Current
where U= supply voltage, Fwd.LED = 3.3V and Current = 300mA, these are the parameters which have been already explained in the previous sections.
Therefore R = (12 - 3.3)/300mA = (12-3.3)/0.3 = 29 Ohms.
The wattage of this resistor may be calculated as W = voltage x current = 3.3V x 300mA = 0.99 or 1 watt.
The above calculation shows that for driving a 1 watt white LED safely with a 12V DC source, you would require a 29 ohm/ 1 watt limiting resistor.
For any other voltage value, you may just replace it in place of U for getting the relevant calculated value, the other parameters in the formula would be fixed.
Finally, after the above calculations are done, the connections of the LEd with the DC source may be conducted as indicated in the diagram.
A switch may be added in series with one of the wires to facilitate toggling of the light as desired.
Remember, you can connect more number of LEDs in series as long as the total Fwd.LED value stays below the supply voltage, meaning with a 12V supply three 1 watt LEDs can be used in series since the combined fwd. voltage would be 3.3 x 3 = 9.9V which is below 12V.
When series LEDs are used, the "fwd.LEd" slot in the formula should be filled with the combined values of all the LEDs used, as stated in the above paragraph.
Since 1 watt white LEDs are specified to produce highly intense lights, these tend to get extremely hot within seconds. Heat beyond 100 degrees Celsius would permanently damage these devices, therefore a heatsink should be fitted at the base of these LEDs, or more preferably a heatsink based PCB should be used for quickly dissipating the generated heat from the LEDs.
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