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I have a fairly general question, but cannot seem to find an answer to confirm my thoughts.

I have a garage motor door, and on the top has 4 terminals - 1 and 2 for a switch button to open and close, 3 is COM, and 4 is +24VDC.

enter image description here

I want to add a little module that will allow me to connect to the garage door and control it. Most modules I can find are 5VDC, and there are some that are 12VDC.

My question is, the garage door states it is +24VDC, does that mean I cannot use a DC converter to change it to 12/5VDC as there is no negative?

I was intending to use something like this: https://www.andymark.com/products/power-converter-12-24vdc-to-5vdc to do the conversion, but the lack of both poles is throwing me especially when the output will be to a USB powered 5V.

This is a diagram from the manual of the circuit board: enter image description here

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    I suspect that com is the ground reference terminal ... it is negative in relation to the 24Vdc terminal – jsotola May 20 at 0:01
  • "Com" (short for "common") is a better term than "Ground" in many cases - with much electronic equipment, "Ground" does not actually imply a connection ot the earth - it is just used to indicate the point in the circuit that the designer intended to use as "Zero Volts" – Peter Bennett May 20 at 0:07
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"COM" is short for "common". It means ground, or, in this case, negative.

  • Awesome! Thanks Tim :) Everything I read stated it was ground, which to me is Earth and was throwing me out – Ahhhhhhhhhhhhhdfgbv May 19 at 23:59
  • Since this is also an AC mains powered device, the DC electronics guy's friend "COM/GND/Vss/Earth" (normal DC current return) must be distinguished from equipment safety ground (never a mains current return except during a fault, and safety shield only). There would be no, um, earthly reason to connect Vss/COM/GND to mains safety ground, because there are things that can go wrong with mains ground that may throw 230V onto it. Your DC stuff would not like that. – Harper - Reinstate Monica May 20 at 0:40

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