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Mini USB 3 LED Lamp Review

Rating: Five Star Rating

Remember when white LEDs first hit the market? Even after they were on the market for a while, they remained a fairly expensive novelty, especially as compared to the more traditional colors and even the blue LEDs upon which they were based.


My, how things have changed. White LEDs today are finding applications in practical incandescent light bulb replacements and many electronic devices with LED indicators will have at least one that glows white. The prices have also fallen through the floor.

USB 3 LED Light

At ninety-nine cents apiece including shipping for a light like the one shown above, oh boy have they ever. I bought five, because at that kind of price, who cares if they aren't that great? (In case you're wondering and just can't wait...these things actually do seem to be pretty decent.)

Like other cheap Chinese bric-a-brac, these lights are sold under a multitude of names and by dozens of different sellers. Should you want to purchase one (or more) of your own, try this eBay link. Just make sure it correctly targets your place of residence, to avoid any shocking shipping or currency conversion fees. If you are a bit more liberal with your search terms, you will find USB LED lights in every shape, size and almost any color imaginable!

How They Work

Standard USB 1.x and 2.0 ports have four pins, two of which are used to deliver five volts DC and a connection to ground. The other two are used for data transfer. While the data pins are less interesting in this discussion, an attached device also uses them to indicate its desired communication speed with the USB host controller. USB 3.0 ports have more pins, and the optional capability to deliver more current, but for the sake of this discussion, they are close enough so as to be the same as their predecessors.

In the land of official specifications at least, USB devices are guaranteed a minimum of one hundred milliamps worth of power at five volts DC. Any device wanting more has to specifically request it from the USB controller and its controlling software. While there might be devices or USB host adapters that actually comply with the standard and do this, USB root ports (the ones on your computer's front panel, motherboard or an expansion card) generally just supply the full five hundred milliamps worth of current to any device, without that device having to request more power.

Thus you can power a great many low current devices from a USB port, so long as those devices are able to run from five volts DC. There is no need at all for the data pins in the USB connector to be hooked up to anything.

Some USB ports will happily supply more than the 500 milliamps indicated in the specifications. Some won't. Most USB ports are protected against stupidity to varying degrees with either a fuse or a self-resetting protective device. The self-resetting circuit protector may or may not sacrifice itself in the name of protecting the USB port. Sometimes, by which I mean "all too often", the fuse or circuit protector survives while a nearly impossible to replace or expensive part like your USB host controller takes the hit.

With this realization, thousands of different USB powered doodads have hit the market. You will find everything from cellular phone chargers, fans, and lights, all the way to missile launchers.

Do They Work?

I'm pleased to report that all five of the lamps I got arrived in functional condition. There was the small matter of the mail carrier having dropped the envelope in the street seemingly without noticing, but that's hardly the fault of the seller. In a rare departure from my usual kind of luck, some people passing by noticed the envelope, picked it up, and delivered it the remaining few feet to my door.

As with any sort of cheap gadget, quality control may be nonexistent. If you've got a lot of USB doodads and wish to run them all at once, or find yourself wishing to test them without potentially damaging your computer, a cheap powered USB hub whose AC adapter is connected and plugged into a working outlet might not be a bad idea. If something bad happens to the hub, it's easily replaced.

Upon connection, these LEDs were strikingly bright. They were certainly too bright for direct viewing. After about half an hour worth of operation, I noticed that the casings were quite hot to the touch. With no instrument more precise than my own "highly calibrated finger", I'd guess that the temperature was around 122F/60C. The LED elements themselves were probably somewhat hotter than that.

Technical Details

LEDs require the use of an external current limiting resistor. Without this resistor, their current draw will skyrocket as they warm up and the eventual result will be out of control current draw that eventually kills the LED (or rather, turns it into a "DED", or "dark emitting diode"). A USB host controller might not look too kindly upon this ever increasing amount of current draw. There are current limiting resistors present in these lights (15 ohm surface mounted types).

Given their heat output and extreme brightness, my guess was that each of the three LEDs on these lamps were being driven quite hard. I was curious to see if the current being drawn was within the USB specifications. Checking the current would be rather hard for most people to do, as it would require hacking up a USB cable to allow for power measurements. Luckily, I have just the perfect USB gadget for this task...an inline voltage and current meter!

USB Current and Voltage Meter
For all I know, it might even be accurate.

Using it suggests that these LEDs are pulling somewhere in the neighborhood of 330mA, or about 1.6 watts. This figure doesn't actually change too much as they warm up, and boy do they ever! Pointing an IR thermometer at the LEDs gave me a reading of somewhere around 65 C (~150 F).

These LEDs are being driven hard to say the least, at 110mA per unit. (I presume, but was uanble to confirm due to an unusually crappy multimeter, that the LEDs and their resistors are in series with one another. At least I hope they are, or the darkness is going to be coming very soon for them.) Looking at the datasheet reveals an absolute maximum forward current of 150mA. Even so, I think they ought to last pretty well, provided the heat doesn't reach a point where the LEDs gradually deconstruct themselves over time. They might suffer phosphor burns from the intense emission of the underlying LED, but I suspect that will be the extent of the damage.

How Well Do They Work?

I think they work very well. Here's the part of the review where those of you seeking pretty pictures to look at it will be saying "FINALLY!" These were taken with a Sony DCR-TRV33 Handycam having decent low light sensitivity. I did not enable color slow shutter or the Nightshot system. Despite its boasting about the presense of a "megapixel" image sensor, I've got my doubts that it's really laying that much detail down into these pictures, especially after the JPEG compression got done with them.

Here's a look at one of the lights, plugged into a USB hub in the middle of a pitch black room. Click the picture to see it larger.

USB 3 LED light, plugged in and illuminated

Here the camera tells things as they are. Look at one of these things and it will be painfully bright! You will have a dark spot in your vision for quite some time afterwards. There is a LOT of light here.

Now, a shot taken from across the room, without a direct look at the light (to try and avoid confusing the camera's automatic metering and exposure control). This picture may also be clicked to see it larger.

Output from a USB 3 LED light from far away.

Things get a bit more subjective here, making analysis of the results much more difficult. Everyone's vision is different and as we age, our ability to see in low light naturally decreases. It's possible for a person to suffer from "night blindness" and not even be aware of it. Cameras and camcorders in particular tend to err on the conservative side, as image sensor noise limits how long they can hold their shutter open before the noise takes over. Even to the camcorder's point of view, though, there is detail in the picture. You can make out a few things, and there's even some reflection taking place from a shiny metal shelf situated a few feet away from the central light source. LEDs tend to produce very concentrated light (as in the picture above). Even so, these fan out pretty well.

These will, of course, destroy your night vision instantly if you catch even the slightest of a direct look at them. They should be quite dimmable, if your application so warrants.

The particular human (a truth in more than one way!) writing this review would tell you that he could read and see his way around fairly easily with the amount of light available. With five of these things running, not only would he need to find another USB port to power them all, he'd also have a pretty decently lit room.

These things would make great sources of lighting for bedtime reading, inside a camping tent, or anywhere else low power high efficiency lightning is needed. Put one on a stalk and there's a keyboard lamp for your laptop! You can even attach them to your keyring if you want, there's a ready cut opening right there in the case! They seem passably well made. In my usual style, I started this review the moment I got these lights, stopped working on it and finally came back to it after a few months. I've used these lights a lot. Not a one has broken or failed.

At one US dollar apiece, these things are a great deal. As well as they seem to work, and as much light as just one of them throws out, they're a no brainer. Highly recommended.


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Review and photography Copyright 2015 by William R. Walsh. Some rights reserved. Please view the terms and conditions, available from the top level page of this server, to see the terms governing the use of this material. Written September 7th, 2015.