I have two MERP 12 24 126 GR rotary encoders from Knitter-Switch. The only information i can find regarding this encoder is here http://www.knitter-switch.com/pdf12/E-2012-MER12-MERP12illuminated.pdf

However I'm not able to figure out which pins needs to go where except for the output ABC pins. Where do i connect GND and VCC? Does it needs both etc?

Through testing it appears like pin 1 is GND (at least for the LEDs) and pins 2 & 3 are the two LEDs. I havn't been able to get any output from A, B or C at all.


1 Answer 1


As per documentation, connections would be following:

A — A line of encoder, use pull-up with controller input pin.
B — B line of encoder, use pull-up with controller input pin.
C — GND of encoder part

5 — VCC for LEDs and pushbutton
3 — pushbutton - one could use 10k pulldown since it seems it is switched to VCC

1, 2, 4 — LEDs

The LEDs have an "always present" VCC on pin 5 - so you would light them up by pulling their respective pin to GND with appropriate series resistor (470R - 1k2).

  • \$\begingroup\$ I only have A, B, C and 1, 2, 3, 4. I'm pretty sure you are looking at the wrong encoder & page. My encoder looks like the MERP12-24121BG on page 2. \$\endgroup\$ Commented Mar 16, 2014 at 15:58
  • \$\begingroup\$ I'm looking at the schematic in datasheet you had linked. Seems your encoder has only two LED's or doesn't have a push button. \$\endgroup\$
    – Rok Jarc
    Commented Mar 16, 2014 at 16:35
  • 1
    \$\begingroup\$ Yes, only two LED's and one button, so four pins on top. I finally figured it out though. Encoder connections are connect as you said, then 1 = GND, 2 = LED, 3 = LED, 4 = Button. \$\endgroup\$ Commented Mar 16, 2014 at 17:00

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