Review on 🔌 Qunqi 5pack MP1584EN Ultra Small DC-DC Step-Down Adjustable Module Buck Converter - 3A Power Supply for Arduino, Supports 24V to 12V, 9V, 5V, and 3V by Jeffrey Kue

Dangerous high voltage when starting. With a module set to 5V DC, I saw instant readings of 7 and 8 volts with my DMM immediately after powering up the module. When I check with my dual trace oscilloscope, it was indeed 8-10V. That's enough to fry a few chips. At the very least, it puts a strain on them and leads to an early death. With a misfortune, I decided to check everything from this supplier and another supplier that I have that are not installed in the device. All showed the same high overvoltage at startup. Time to replace them all. At least that's what I noticed before I sold a work of art with it. My previous review: Works as advertised, but that tiny one-turn potentiometer makes voltage adjustment difficult, so I gave it one star. I added a point because you can use a constant resistor instead of a 1 turn potentiometer. Warning: If you mod a DC/DC converter module and kill it, that's your problem. Don't expect them to replace it. The following description assumes that you will not change the PCB layout or resistor values in the future, and also assumes that you have a working knowledge of electrical circuit design. This is also not a complete solution. This is not the place to teach or do it. Tracing the circuit, I see an unused surface mount resistor connected to a feedback pin on one end and a V+ output on the other. The 1 turn potentiometer also offers a half voltage divider to adjust the voltage. The MP1584 switching regulator datasheet shows how to calculate the resistor values of the voltage divider. After removing the 1 turn potentiometer I measured the resistance of the 8400 ohm fixed resistor. According to the marking on the microcircuit, it is written that this is an 8200 ohm resistor. Using the equations from the datasheet, I calculated 44.1kΩ as the ideal value for a 5VDC output, but this is not a standard value in my 5% resistor collection. So I chose the 47kΩ resistor because I can use a trimmer resistor to lower its RMS value. After soldering in I get 5.23V. I then selected and tested a much larger resistor in parallel with the 47kΩ resistor and ramped the output voltage down to 5.00V with a 2A load to get more accurate fixed output voltages.