transistor used as a button

Question

Hi,

Im using a transistor as a button that is pressing a button on a hacked keyboard.

Heres how the hacked keyboard works (that is the small PCB iside the keyboard)-

Now what I want to do is use a transistor to connect the pins and get a letter.Heres how i did it .My questios is it correct couse im having some issues

with it like getting random letters or not getting any at all.

YT2095 · Accepted Answer

it`s not a Bad idea, but the use of a 4016 or 4069 would have probably been better and more like an actual switch.

you`ll have to get the timing right too (within reason) else you could either Miss the scan or hit it twice for instance.

it May be an idea to also bias the transistors base down to deck to preclude any spurious triggerings/noise.

YT2095 · Answer

yes, it`s just like your transistor idea in principal, but will be seen more like a propper key press, and of course it`s bi-directional, so it doesn`t matter what side goes to where (unlike a transistor).

the 74125 will do the same and there is 6 of them on a chip, but these Are directional, so you`ll need to know the Scan lines from the inputs, and of course these are 5v only devices.

YT2095 · Answer

well, this chip does have limitations in that there is a small resistance across the switch when "closed" and natually it`s current carrying capacity will be significantly less than that of a metal-on-metal contact (as in your relay). but they`re cheap enough, and worth carrying in your arsenel of parts even if it doesn`t quite work out for you in That particular application.