Preview Switching Regulator LM2596 with Voltmeter cheap modules out there.

They are look the same but they are not. I tried to check from the user’s feedbacks.

Model 1 Fewer.png

Model 1

These one is the cheapest and have fewer components. Maybe it’s the first generation.
Use an inductor 100µH. It has green LED power.

The left button use to turn on/off voltmeter.
The right button use to switch between input and output voltage.

There is a blue PCB version which slightly differences.

Model 7.png

Model 2 MH.png

Model 2 (MH)

It shows leading zero. Use an inductor 47µH. Both input/output LEDs are red color.

Use only one button for all functions.
Short press = switch between input and output voltage.
1-2 sec = calibration
3 sec = on/off voltmeter

The PCB is bigger than another.

UT8yu_CXztaXXagOFbXk.png

Model 3.jpg

Model 3

Use an inductor 33µH. Both input/output LEDs are red color.

Model 4.png

Model 4 (2596-SDC)

Use an inductor 33µH. The output LED is green color.

Model 5.png

Model 5

Like the model 1, has two buttons but come with more components.
Use an inductor 33µH and input capacitor 100µF.
Both input/output LEDs are red color.

ETC

Model 6.png