Review on PEMENOL DC-DC CNC USB Step Up/Down Power Supply Regulator Module: Adjustable Boost Buck Voltage Converter with Digital Display Voltmeter Ammeter and Battery Capacity Tester by Daniel Shankle

In PER mode, the actual output voltage changes faster than displayed. The display is a bit slow to catch up. Absolutely no problem. I was able to get up to 24.5V over USB, but didn't connect a load. I was concerned about the USB port in my computer. The output voltage is pretty close to the voltage reading on my old school multimeter. I believe the measurements were within their margin of error. The VAH mode offers a very simple voltage/power/current meter. The instruction manual included in the package does not work. The link on the Revain website works and is quite detailed. Three power modes of the device also do not hurt. I would have liked reverse polarity protection. The device is solidly built. I plan to use it in Arduino projects where current requirements are not that high and I can quickly switch between the power supply and the multimeter to measure voltage/ammeter. The device is small enough that I can tie it to the breadboard with short wires. I also have a 5.5-30V to 0.5-30V, 60W, 5A version. It's not as compact but offers an extra ease of use in terms of voltage control. It has only one input port and one power port. No USB inputs or outputs. The exit is also a terminal. The two output change buttons are very useful. The handles are sensitive and easy to use. The display is a bit slow to catch up. The documentation associated with Revain is descriptive to get you started. The device came with separate components and required assembly. There were no instructions in the packaging. I had to look at pictures of Revain to figure out how to put it together. The fan didn't work either. I didn't use much power so maybe it kicks in as the device heats up. All in all a very easy to use and very useful module.