Author Topic: Do you need add resistor in a keyboard matrix if a switch max current is 1mA?  (Read 1385 times)

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Offline Kaibz

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  • Posts: 48
  • Location: AFK but not too much
I guess my question is hard to summarize in one line for a title....I have build a keyboard using a 14X7 matrix + Teensy + TMK Firmware + CherryMX brown.

It works great but, now i would like to replace some of the keys by an omron D2LS micro switch https://omronfs.omron.com/en_US/ecb/products/pdf/en-d2ls.pdf

The problem is that, this micro switch seems to have a max current rating of 1mA.

So i am wondering if i need to add a resistor for those switches in the matrix, as the teensy 2.0 uses 5V, may be using a:

(5/0.001) 5Kohms resistor would make sens? Or is it simply not needed in a Matrix?

Update: link to screenshot of the matrix i am using with a Teensy 2.0:

https://imgur.com/zMlsHNq
« Last Edit: Mon, 30 December 2019, 20:07:44 by Kaibz »
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Offline piit79

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There's no need for any resistors - digital input pins have a very high impedance (in the order of megaohms IIRC), which means the current flowing through the switch into the pin is negligible (microamperes).

By the way, the screenshot of the matrix seems to be broken.

Offline gipetto

  • Posts: 83
iirc the pullup resistor in a teensy 2.0 is about 14k ohms.

Offline Kaibz

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  • Posts: 48
  • Location: AFK but not too much
Thank you very much.
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