New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Ability to use Pi's internal pull up/down resistors for digital inputs #19

Open
wants to merge 1 commit into
base: master
from

Conversation

Projects
None yet
2 participants
@kiddigital

kiddigital commented Sep 3, 2018

Added ability to use RPi's internal PULL_UP/PULL_DOWN resistors for digital input. Extended Input example.

@Gadgetoid

This comment has been minimized.

Show comment
Hide comment
@Gadgetoid

Gadgetoid Sep 11, 2018

Member

Interesting- what's your use case for this?

I was originally concerned about the voltage divider the 50K pull-down would create with the 20K current-limiting series resistor but - if my maths serves me correctly - it only lifts the minimum required voltage for a stable "HIGH" to around 2.5v.

Member

Gadgetoid commented Sep 11, 2018

Interesting- what's your use case for this?

I was originally concerned about the voltage divider the 50K pull-down would create with the 20K current-limiting series resistor but - if my maths serves me correctly - it only lifts the minimum required voltage for a stable "HIGH" to around 2.5v.

@kiddigital

This comment has been minimized.

Show comment
Hide comment
@kiddigital

kiddigital Sep 17, 2018

@Gadgetoid , my original use case is a doorbell.

I used the available 5volt of the Automation HAT directly for my doorbell switch connected to the digital input of the Automation HAT without any pull-down resistor. Because of the floating-ground issue, the readings on the input where not reliable but after activating the internal pull-down resistor of the Pi, the input is now reliable.

Also I use it now for a second use-case which is a 12volt motion detector which gets is 12volt from an external source and pulls a second 12volt line down when it detects motion. Here I also needed to activate the internal pull-up resistor on the analog input to get a reliable reading (same floating-ground issue I assume :) ).

kiddigital commented Sep 17, 2018

@Gadgetoid , my original use case is a doorbell.

I used the available 5volt of the Automation HAT directly for my doorbell switch connected to the digital input of the Automation HAT without any pull-down resistor. Because of the floating-ground issue, the readings on the input where not reliable but after activating the internal pull-down resistor of the Pi, the input is now reliable.

Also I use it now for a second use-case which is a 12volt motion detector which gets is 12volt from an external source and pulls a second 12volt line down when it detects motion. Here I also needed to activate the internal pull-up resistor on the analog input to get a reliable reading (same floating-ground issue I assume :) ).

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment