# Open collector

**URL:** <https://community.openenergymonitor.org/t/open-collector/6439>\
**Category:** Hardware\
**Created:** [1 February 2018 12:07 UTC](https://community.openenergymonitor.org/t/open-collector/6439 "2018-02-01T12:07:54Z")\
**Posts on this page:** 1\
**Showing post:** 17

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**Author:** ![CelsoHenriques](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/celsohenriques/32/9586_2.png) [@CelsoHenriques](https://community.openenergymonitor.org/u/CelsoHenriques)\
**Post date:** [9 March 2018 23:03 UTC](https://community.openenergymonitor.org/t/open-collector/6439/17 "2018-03-09T23:03:34Z")

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Now that you explain that, i can see how it works.  
How did i miss this(???):  
“So if you wire the switch between input and ground, so the switch pulls the input to 0 V when it’s closed, you need a “pull-up” resistor to pull the input up to 3.3 V or 5 V when the switch is open. And vice versa”

I really need to read carefully this [Directly connecting to Optical Pulse Counter with RPi? - #7 by pb66](https://community.openenergymonitor.org/t/directly-connecting-to-optical-pulse-counter-with-rpi/1294/7)

Robert, i am very grateful for you help!  
Thank you!  
Celso

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