DEVMO 2PCS XL4015 5A DC Buck Step-Down Adjustable Voltage Power Module Converter with LED Voltmeter

products work - take care with them they are delicate - the parts on board will break off without any force at all being applied - one of the main parts broke off - i can fix it - but it was my fault

It is a nice design, very compact. Stable output over 24 hours ( did not check how stable is with temperature). The voltage was a bit difficult to set - I wish the adjustment trimpot had multi-turns and the display were capable of 0.01V resolution.

I have discerned that the left button turns the display and LEDs on and off and functions as a "decrease" button for the adjust mode. The right button switches between showing the input voltage and presumably the output voltage. A long press of the right button will cause the screen to start flashing, and from here you can adjust either the output or the input (???) voltages. A long press of the right button again will "save" this value. However, as far as I can tell, nothing will actually affect the output voltage other than the input voltage - I have been unable to get either buck/boost converter to output anything other than its input voltage through any combination of inputs. Therefore, I think the product is faulty or a scam, seeing as neither of my two products worked and it is pretty unlikely to be a coincidence.EDIT: they work fine, rotate the potentiometer at least 20 times counter clockwise if it doesn't change the output. I got these instructions in another similar product's box and figured I would try it on these and wouldn't you know it worked.

Lo monté en una caja plástica para sustituir el cargador de la batería del voxc blower/trimmer averiado y fácilmente lo alimenté con un transformador en desuso de 24 y lo regulé a 20 volts.

Simply did not work wish I could find Product made in a more reputable country... couldn’t give 0 stars

Product came missing a capacitor, from what I can tell it was ripped off sometime before it was packaged because it wasnt in the bag or box, bad quality control

Seems to work well, had to figure out a number of things the hard way though. I was about to give up until I read another review about turning the potentiometer counter-clockwise a LOT. Without that, I was getting output voltage equal to input voltage only. Another tip about holding down the right-side button came in handy later. Thanks to those reviewers!!This system board seems fine. The bottom looked pretty rough, but it was difficult to capture in a photo. I used an adjustable power supply and multimeter to verify. I also used a simple resistor and LED for an additional confirmation and load.The input side matched on both device displays and with the multimeter. There's a red light near the input connections to show you're displaying the input voltage. The left button (nearest the input side) only toggles the on-device display on and off. There's also a green light indicating power is being received. Compared to others I found online while looking for instructions, this seems to be odd with the single adjustment.To check the output side, you depress the button nearest the output side. This will switch the display and the bright red LED on the board on that side will light up and the input side goes dark. This was where I did the press-and-hold and was able to adjust the output display a little, but it would just go in a loop and the measured output never changed. The actual solution at this point was to adjust the potentiometer. It must have been bottomed out because it seemed like more than 30 full rotations in a counter-clockwise direction. Eventually I did see the voltage output start to change.This was the stage I grabbed some photos with the help of my daughter. The right button allowed me to swap back and forth between input and output on the display. However, the voltage was off by 0.5V on the output. Knowing this, I was able to adjust the output to what I wanted. So, with 4.6V on the display, I was getting 4.99V output at my LED with input still at 11.1V. I did try a number of different output voltages and it was consistently off by the same 0.5V and did not scale as a percentage.I did not get photos of it, but there is where I was able to hold down the right button for a few seconds. Upon releasing it, the display would be flashing. At this point, you can use the left button to decrease the value shown on the display if it is off. The right button will increase about 0.5V before it loops around. So, at my 11.1 input, I could have adjusted that to show as low as 10.5 or as high as 11.5, but it seemed accurate. The output side adjust was off by the full 0.5V but this could be corrected. Pressing and holding again would go back to the standard mode.