4 x 3 Matrix Array 12 Switch Keypad Keyboard Module 12 Key MCU Membrane Switch Keypad Compatible with Arduino

These cannot possibly have worked for anyone.Mine didn't so I took it apart to investigate (don't thank me ... you're welcome)#1 The pins are not in a logical col 1 2 3 row 1, 2, 3, 4 order. Oh no.#2 Some tracks are incomplete and result in no connections! eg pin 6#3 Only 4 buttons had the necessary pair of connections (the 1, 2, 6 & *)#4 Even these failed to make a short when the button is pressed.#5 Resistance varied between 500 and 200 ohms, preventing software from recognising a key press.I give up. Just don't buy these. (Note the same item from Flux has the same issues)If you are real person who has successfully used one of these I'd be interested in how.

well made nothing to dislike

Schematic was incorrect (and non standard for these types of keypad) requiring some reverse engineering to get the pin out right, and "on" resistance was very high (~100s of ohms), but otherwise mechanically sound and worked as I needed.

Also mentioned by others, the layout is not standard.C1,C2,C3R1,R2,R3,R4rather (looking at keypad side right to left:C1 = pin 3 ,C2 = pin1 ,C3 = pin5R1 = pin2 ,R2 = pin7 ,R3 = pin6 ,R4 = pin4

In line with another review by MikeK, there is no logic to the conections and not all of the buttons work at all.This is a very poor product which is simply not worth the bother!