Tested all out of the box and found no issues

Well made, great functionality. The resettable fuze is a bit large and isn't secured well, I desolder it from the top side of the board and re-solder it back in on the bottom side of the board, and lay it flat on that bottom side, it's not likely to get in the way there.

Works great on 12 volt fan

I am going to use these for a variable speed fan setup on a portable reefer/freezer bottom to top air circulation system with 5V USB. I tested all and everything checked out OK!!! PS--I was looking for the smallest possible "package" and this seemed to be the most optimal based on layout and the connecting terminal positions. Thanks!

Ok, it's a PWM controller. It does indeed control stuff with PWM... more or less. Here are the caveats:1) 10kHz... nope, try half of that (about 4kHz). Thankfully I don't care, and again to be fair I'm operating at 3.7V. Maybe at 12V it produces 10kHz, but I doubt it.2) 5A... uhh, well, the eagle eyed may notice that the resettable fuse on the board is marked "250", which means it's a 2.5A fuse. To be fair these fuses only trip at around 5A, so it can kinda sorta do 5A input current for a bit. It probably can really do 5A output current, since the output flyback diode is rated 5A, so that's nice. But yeah basically divide that spec by two as well.3) I wanted this for a 1S (single cell) lithium application, so the 3V rating was attractive. So I soldered across the "3-15V" jump link. However at even 3.7V (50% charge for lithium), the transistor isn't really turning on all the way. See the first oscilloscope picture. That's supposed to be a square wave! The transistor is burning about half the applied power as heat, and can't put out more than a couple volts at 2.5A. The NE555 timer producing the gate control signal is only rated to run down to 4.5V (to be fair it does actually oscillate still at 3V) and it's only rated to put out supply-1.4V. And the transistor is rated with a _threshold_ voltage of 2V! So the transistor is barely even trying to start conducting at 3.7V supply. Oooff. Well at least as the transistor overheats the threshold voltage drops and it conducts a bit more. So we've got that going for us, which is nice. Claiming that this thing runs at 3V is really quite a stretch.4) Despite having a nice "click-twist" knob that turns off the PWM circuitry when you twist it all the way to the left, this power switch feature inexplicably does not disconnect the 78L05 regulator (true whether or not you've jumped over it for 3-15V operation using the solder jumper). So this thing draws about 3mA all the time, and would drain a typical crummy single 1500mAh 18650 cell from full to empty in 20 days. Maybe not a big deal, but why would they not just switch off the darn regulator too? Arrrgh.Ok, now all this said, the device basically has all the parts one needs for PWM. For operation at 5V-12V, it should work fine with the "3-15V" jumper soldered. For operation at 7V-30V, it should work fine as is (the regulator only is rated down to 7V, so don't believe the "6-30V" hype). And, even at 3V-4.2V, it can actually be made to mostly work (although don't expect more than a couple amps out of it).To fix the silly design for low voltage use, it just needs a pull-up resistor to help the poor old NE555's output reach closer to the supply voltage. See the included reverse engineered schematic of the device. The pull-up should be 1k for 3-4.2V operation (or anything up to 7V) and the jumper installed, or also for use without the jumper. If using the jumper from 7V-15V then 1k starts getting a little bit too toasty if the resistor is physically small, and maybe a 4.7k would be better (although the improvement won't be as great). See the two shots of the board for installation locations: those comfortable with SMT soldering can install an 0402 1k resistor between pins 3 and 4 of the IC. Those handy with through hole parts can install a 1/4W axial resistor between the transistor gate and the output of the power switch as shown. And finally check out the 'scope "after" shot: almost square! not bad.Then, when operating with the "3-15V" jumper soldered, the 78L05 regulator also can be removed entirely and plopped into the spare parts box for another use, saving 3mA of constant drain. Just take a big chisel tip soldering iron and put a big blob of flux cored solder across the three small pins all at once, wait for the whole part to heat up (doesn't take more than 5 seconds because there's barely any copper traces under it) and just wipe the whole part off the edge of the board with the iron.The one spec which doesn't really need to be divided by 2 is the operating voltage. I mean, don't get me wrong, it would be crazy to operate at 30V. The transistor is only rated 30V Abs. Max; that's a recipe for disaster. But it could probably really operate at 24V just fine.TL,DR: a decent 5V-24V, ~3A, 4kHz PWM controller that can be coerced to do 3V-4.2V, 2.5-3A with modifications.

I had an old computer (Atari) with bad LED power and hard drive lights. The new replacement LEDs were way too bright. I put one of these inline on the wiring and now can adjust the brightness to a more realistic brightness.

none of them even remotely work only flash on and off and the knobs don’t even work I tested all of them complete garbage product

Trabajan muy bien, tiene un giro muy amplio, los probé con bastantes leds y dio un buen desempeño, no calientan, lo que no me gusta para nada, y lo considero ilógico es la posición de los 2 puntos de entrada y salida de voltaje, no entiendo porque la entrada (POWER) esta en los 2 extremos, y la salida (Output) esta en el centro, los cables quedan cruzados, sería mucho mejor si la entrada y salida estuviesen 2 puntos en la izquierda, y los otros 2 puntos a la derecha, y listo, asi la instalación quedaría más limpia, y sin cables cruzados, los simbolos de voltaje + y - deberían estar impresos en la parte de arriba, y no abajo, ya instalados los cables, no se puede identificar la polaridad, a menos que se use cable de diferente color