I can't comprehend the idea of using switch to groung pin to get logical 1

Ground switched circuits like this horn switch were used in automotive circuits for 80 years.

schemeit-project(1).png

schemeit-project(1).png

And the point about that last circuit is that the user doesn't know, nor do they care, what actually happens under the hood (literally). All the user needs to know is, press to toot.

If it was wired in such a goofy way that the driver had to hold the horn ring pressed to keep it silent and release to toot, that would be a very different discussion.

I always wondered if the "hot wire -> switch -> light bulb -> neutral" scheme was etched into the brain at conception, like a dim genetic memory from a previous life. :slight_smile:

but now you can just plug fluke to ground on fuse box and just go trought all connections.

Have you ever tried putting one Fluke probe on the "hot wire" and probing the circuit with the other?

JCA34F:
Have you ever tried putting one Fluke probe on the "hot wire" and probing the circuit with the other?

Once in while, some time ago I did it when in tight spot, I kept other test prope badly and somehow touched it... while another one was still on live. it still hurts bit too much even it go thru fluke. :smiley:

Dont think that current would be more than some mA or even bit less. but when you are inside relay logic case, you dont want anything extra :smiley:

Also apart to get stronger current sink when cutting 0 (was mentioned before) , its also easier just cut 0 when playing with npn transistor switches. no need to worry voltage that is cutted (ok, can be done also with pnp to cut 12V, but you need to be sure about that voltage.