# Are there any unused pins on the Arduinos?

**URL:** <https://www.evolver.bio/t/are-there-any-unused-pins-on-the-arduinos/269>\
**Category:** Motherboard\
**Created:** [February 22, 2021, 9:24pm UTC](https://www.evolver.bio/t/are-there-any-unused-pins-on-the-arduinos/269 "2021-02-22T21:24:07Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Nate\_Borders](https://yyz1.discourse-cdn.com/flex035/user_avatar/www.evolver.bio/nate_borders/32/268_2.png) [@Nate\_Borders](https://www.evolver.bio/u/Nate_Borders)\
**Post date:** [February 22, 2021, 9:24pm UTC](https://www.evolver.bio/t/are-there-any-unused-pins-on-the-arduinos/269/1 "2021-02-22T21:24:07Z")

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Continuing the discussion from [Purpose of 'Acknowledge' Command](https://www.evolver.bio/t/purpose-of-acknowledge-command/268):

After a [bit more finagling](https://github.com/nb-e/evolver-arduino/blob/main/SAMD21/Rev%20C/RS485_OD_LIGHT_switching/RS485_OD_LIGHT_switching.ino), I was able to get my LED to turn off before taking OD and then turn back on after. Success!

In a similar way, I want to turn off pumps that I’ll be using to bubble air into the culture.

I’m assuming that I need to minimize lag time with the whole on/off routine, so I need to control these pumps using the same Arduino that does OD and light. Otherwise I would have these pumps on the fluidics module and have a communication with the system there.

I’d be controlling the pumps (which run off of wall AC) via a relay, so that the 12V eVOLVER architecture could turn them on and off.

Therefore I see two options:

1. Plug the relay/pumps into the circuit that’s controlling the light.

2. The simpler option? Run the relay off of one of the pins on the arduino

**My question: are any of the pins on the Arduinos not being used by the two sub-boards?** I can’t seem to find current layout of the motherboard on the github

I would also love general design feedback on solving this problem because I’m really just starting to learn electronics.

Thanks in advance for any help!

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**Author:** ![heinsz](https://yyz1.discourse-cdn.com/flex035/user_avatar/www.evolver.bio/heinsz/32/52_2.png) [@heinsz](https://www.evolver.bio/u/heinsz)\
**Post date:** [February 23, 2021, 3:27pm UTC](https://www.evolver.bio/t/are-there-any-unused-pins-on-the-arduinos/269/2 "2021-02-23T15:27:00Z")

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Hi Nate,

Can you post a simple schematic of what your setup looks like? I’m not sure if I totally understand what you are describing here.

Zack