Some months ago a local store had a whole pile of these AAA battery powered LED lamps that you could mount pretty much anywhere:

LED lamp that looks like a light switch
Back of LED lamp that looks like a light switch

They weren’t all the same – some had contacts for three AAA batteries, some had contacts for four, and there were a couple of different brands. They all looked pretty much the same, though, and were surprisingly bright (some had cheap batteries in them from the factory I guess) and really, REALLY inexpensive.

I bought a few of them, took them home, and puttered around with them. Some had a resistor in them and some didn’t. I tried running one off my bench supply set to the right voltage and they started to smoke. Even with a set of AA batteries instead of AAA they got pretty hot. So… not only were they cheap, they were counting on folks using AAA batteries with a particular current capacity/internal resistance. Not sure if that’s clever engineering or just super cheap.

I was really impressed with those Chip on Board (COB) LEDs, though. Even with the batteries from the store in them they were crazy bright. I went back to the store and bought out the rest they had, thinking I’d take them apart and use the LEDs for other purposes.

And then they sat.

Fast-forward to a couple of days ago. I have this snazzy little gooseneck-mounted magnifier and wanted to turn it into an illuminated one. I tried a couple of different approaches and wasn’t happy with them. Then I remembered those switch lamp things.

Taking them apart is easy, it’s just six screws on the back (two are under the sticker), and then the whole thing pretty much falls apart until you’re left with this:

LED lamp disassembly showing internal parts

A slide switch, some wires, two COB LEDs mounted to a plastic reflector, and sometimes a resistor (this one didn’t have one).

Snip the wires and the plastic “rivets” and the LEDs come off easily:

LED lamp showing removed switch and LEDs

Notice how there is one red wire, one blue wire, and two white wires? There is a positive and negative terminal on both ends of the LEDs. Both positive terminals are connected, as are both negative terminals, so you can chain the LEDs together however you want. In this lamp’s case, they were wired in parallel.

There are two markings that I could find on the LEDs in this lamp and on several others that I tried – “10YQM” and “NT64”:


Each COB has ten LEDs in it and the back of the COB is a nice little aluminum strip that will carry away some heat. Unfortunately, I had no idea how much heat, or how much current would generate how much heat, because I couldn’t find any datasheets (or even information) on these devices.

So, bench time! I set up an LM317 as a constant current source and, starting from 50mA, slowly increased the current until the voltage across the device stabilized, then increased it some more until the aluminum got just slightly warm to the touch. What I ended up with were the following numbers (tested on six of these devices):

Forward voltage: 2.7-2.8V @ 150mA
Forward current (sustained, no external cooling required): ~150mA
Maximum current tested: ~350mA for less than 10 seconds (got hot pretty quick)

I’ve had them running for five hours at a time at 125mA with no problem, and at that power, four of them are plenty bright enough for a desk lamp:

Desk lamp made with 4x LED COBs
It’s too bright to look at it with my eyes but I like this picture because the short exposure shows the individual LEDs in the COB.

They’re wired in series and held on with some masking tape (you can see it in the picture) but I’m printing a proper holder for them right now. Maybe it’ll be the subject of another post.

Anyway, if you have any of those LED switch lamps or some of those 10YQM/NT64 COB LEDs, good news – they’re nice and bright and easy to use!

7 thoughts on “10YQM / NT64 COB LEDs”

  1. Thanks for this post, it is very useful and saved me working out for myself. As you say, there are no data sheets out there, it would seem.

    1. Hmm… on the off chance you’re still working with these things six weeks later (sorry about that)…

      I’m not sure which ones I have, but based on some of the numbers I saw I’m going to treat them as 1W modules – they’re still plenty bright.

      Since they run at around 2.8V you’re not going to be able to run two of them in series from a single 3.6V cell – it’ll have to be parallel.

      Be careful with using resistors to regulate current to LEDs – a constant-current supply is a much better option. If you do use resistors, run the LEDs well below their max power so they don’t warm up too much or the current can run away on you and the LEDs will burn themselves out.

      Thanks for the comment!

  2. Greeting Mark,
    I am another tinkerer who is revisiting my cache of these very same COB LED’s that I salvaged out of cheap “giveaway” flashlights from a popular tool store (wink, wink). Almost all of the flashlights are so cheap that they inevitable begin flickering or just will no longer turn on; even with fresh batteries. Rather than try and troubleshoot these cheap-as-dirt items, I learned early on that the COB LED’s were fine and worth salvaging. The rest of the lights went into the trash. Doing an on-line search by the numbers found on the COB’s led me to your post. I have yet to find a commercially available work light that is versatile and user friendly for putting light in a tight space while working under cars or inside the engine compartment. I figured I could invent exactly what I need to my specifications.
    I have about 35 years experience as a machine designer along with a background in tool and die. Would love to heard how these COB’s held up for you.

    1. Hi Mark! I’ve had good luck with those COB LEDs so far and have used them in a few things including a desk lamp, an outdoor area light for a camera, and a light that sticks to the underside of a sewing machine arm. I haven’t had any fail yet. I don’t run them flat-out, though, and always use PWM or a constant-current source to power them instead of a resistor. I think as long as you don’t run them too hot they should last you quite a while!

  3. Greetings Mark. Thank you for posting this. Taking the time to test and compile useful data for these LED’s. I too have several of these, and couldn’t figure out why some has a resistor and some didn’t. Some in parallel, some in series. So I google lens a pic.(almost the identical pic u have). And wah-la!! Here’s a link to Mark’s bench. If u don’t mind I have a question for you. Being that I’m new at this hobby(my doctor said to get a stress free hobby). I told her I collect stamps😁. Anyways. I’ve got 3 sets of these (6 cobs total). And making a portable work light bar. Not sure if I should run in series or parallel want to use 18650 cell to power it. Any suggestions or instructions would be very helpful. Thanks again for you info on these little guys.

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