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If we search this title in any search engine, many products will show up on your screen. These products have one functionality i.e. to light up when connected to a USB port. After looking at these products for a while, I was ready to make one of these product on my own. It is really simple, believe me.

Lets get started.

Step 1: Design Decisions

We need to make 2 design decisions for our USB led light.

  1. Which LED should we use ?
    • It will depend on the intensity of light we wish to generate from this product. I decided not to go with our normal usage 3mm/5mm LEDs, instead I decided to go with higher luminescence LED (image is attached).This decision was driven by the fact that USB 2.0 can supply up to 500 mA of current, which can easily power this high luminescent LEDs.
  2. What value resistor should I connect in series with the LED to limit it's current?
    • Value of current limiting resistor depend on 3 things:
      1. Supply voltage (In our case it is 5 V i.e. standard USB supply voltage),
      2. Voltage drop across LED and
      3. Amount of current we wish to flow through LED.

In 2nd decision question, we have two unknown quantity voltage drop across LED and Amount of current we wish to flow through LED. Current flowing through LED will decide the intensity of light it will generate. To find out these two variables we shall do a small experiment.

Step 2: Small Experiment

Here are the details about our small experiment.

Here is the list of components needed for doing this experiment.

  1. Bread board,
  2. Multi-meter,
  3. 5 V breadboard power supply (any 5 V supply will work),
  4. Potentiometer ,
  5. LED under test (LED for which we wish to find voltage drop and current required).

Connect these components as per the attached fritzing sketch.

Step 1-

In this step we will find out the voltage drop across the LED. Initially keep the potentiometer at it's full resistance, slowly decrease value of resistance by rotating the nob. Try to attain your desired brightness, make sure that LED is not heating up. Now measure the drop across the LED using multimeter by connecting it in parallel to LED. So this part will give us the voltage drop across the LED.

Step 2-

Now disconnect any one of the wire and put multimeter in series with the circuit in current mode. Measure the current needed for this desired brightness.

We are done with the experiment. Directly measuring the resistance of potentiometer will give us the answer for our ultimate question about the value of resistance or we can use following links to calculate the value of resistance. http://www.digikey.com/en/resources/conversion-cal...

I prefer the former.

In case of any doubt just refer to attached video.

Step 3: We Are Ready

Finally we are set to put all things together.

Following is the list of things needed to build our USB LED light.

  1. General purpose circuit board,
  2. One USB-A male connector,
  3. Two 15cm single core wires (with good stiffness),
  4. LED for which we have calculated desired resistance,
  5. Heat shrink (to cover solder joints),
  6. Solder wire and iron.

Now connect these components as per the attached fritzing sketch.

In case of any doubt just refer the attached video.

Step 4: My Prototype

Here are images of prototype that I have made. Its not that neat, I suggest using a spare Pen-drive casing for final product.

Image of my friend trying to read using this light is also attached.

Thank you for your time. In case of any doubt refer to this video.

<p>This is a very compact one: </p><p>https://www.instructables.com/id/The-Smallest-USB-LED/</p>
<p>great..</p>
<p>cool stuff, i make usb plant lights with the same idea.. i use 1W leds as well (with a heatsink) and 5 to 3V converter module</p>
<p>Wow!</p><p>pls let me know, how many 1w LED can be connected to a USB 5v ?? if possible pls suggest resistor values as well !! Thank u.</p>
<p>you need to use heatsinks if you are going to push the limits; <a href="https://www.instructables.com/id/The-Life-Seeder-make-an-indoor-seed-starter/?comments=all#CZY7ZZCI21R0HIP" style="">https://www.instructables.com/id/The-Life-Seeder-ma...</a></p>
hello.<br> .<br> usbs should always have 5V and between 0.5-1A upto 2A now with USB 3.0<br> .<br> 1W white/yellow LED is 3.3V 0.35A<br> 1W red LED is 2.5V 0.35A<br> 3W white/yellow LED is 3.3V 0.7A<br> .<br> so, if you don't have a voltage regulator you can connect, 2x1W red LED in series first adding upto 5V 0.35A and then in parallel upto 3 times, so you would have 5V 1A total and also total of 6x1W red LEDs from a single USB port.<br> .<br> or you can use a 5to3.3V reducer module ($1) and connect 3x1W white/yellow or again with the same voltage reducer, 2x3W in parallel equaling to 3.3V 1.4A, you would need a decent charger for this. old laptops may not be able to handle. new smartphone charges can.<br> .<br> you need to learn about in series and parallel connections if you don't know so already. . check out this link for a more information; <a href="https://www.instructables.com/id/LED-lights-1/" rel="nofollow">instructables.com/id/LED-lights-1/</a><br> <br>
<p>Great.</p>
<p>Though I like the idea of using a high powered LED with a USB, and have done so myself several times, I can tell you that it needs some sort of heat sink if you want to run it at full current. However, I think you're ok for now as it's only running at &lt;50mA or 15% it's full current. I like the look of it too.</p>
<p>It starts getting hot around 100-200 mA. One should definitely do the small experiment described in instructable, to verify the heating effect for his/her LED. </p>
U can do this with any Christmas tree light and u don't need to use a resistor for it
What LED &amp; what resistor did you use?
<p>one more thing, make sure LED don't get hot.</p>
<p>I used 1w led and current limiting resistor consist of two 100 ohm resistor in parallel but the point is it doesn't matter which LED you use. That's the reason why I included test experiment in the instructable. </p><p>Select which ever LED you like. If it can't achieve required brightness at its full current, go for higher brightness LED. Just make sure current don't exceed 500 mA. </p>
pls post abt Led and the resistor used!<br>is it a 1w LED ?
<p>Yes, I used 1w led and current limiting resistor consist of two 100 ohm resistor in parallel.</p>

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