# Logic controlling ventilation

**URL:** <https://discourse.nodered.org/t/logic-controlling-ventilation/73355>\
**Category:** General\
**Created:** [7 January 2023 23:36 UTC](https://discourse.nodered.org/t/logic-controlling-ventilation/73355 "2023-01-07T23:36:03Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![FSHelgeland](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/fshelgeland/32/64260_2.png) [@FSHelgeland](https://discourse.nodered.org/u/FSHelgeland)\
**Post date:** [7 January 2023 23:36 UTC](https://discourse.nodered.org/t/logic-controlling-ventilation/73355/1 "2023-01-07T23:36:03Z")

</div>

So I need to build a logic controlling my ventilation system. I got three sensors which give me values for co2, moist bathroom1 and moist bathroom2. If one of them get over a certain value they have to trigger the boost function. That is the easy part I think. But the tricky part? is when they all three falls under a certain value at the same time, they have to trigger "home mode". As I have a limit for messages sending to the system, I only want the message to be sent when all three of them reach the correct values, and not to be triggered again before one of the values has been over and then drops again.

So ...  
if co2 \> 1000 && moist1 \> 49 && moist2 \> 49  
then set home mode.

---

<div class="post-metadata">

**Author:** ![craigcurtin](https://avatars.discourse-cdn.com/v4/letter/c/94ad74/32.png) [@craigcurtin](https://discourse.nodered.org/u/craigcurtin)\
**Post date:** [8 January 2023 01:47 UTC](https://discourse.nodered.org/t/logic-controlling-ventilation/73355/2 "2023-01-08T01:47:40Z")

</div>

Have a look at the [node-red-contrib-boolean-logic-ultimate (node) - Node-RED](https://flows.nodered.org/node/node-red-contrib-boolean-logic-ultimate)

these enable you to take a number of inputs and only output when all of them are in a certain state - you do not say where you are sourcing the messages or how they are received in NR - You can also put this inline with a trigger node that will only pass on messages is the output of the boolean node changes

Craig

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<div class="post-metadata">

**Author:** ![jbudd](https://avatars.discourse-cdn.com/v4/letter/j/5f8ce5/32.png) [@jbudd](https://discourse.nodered.org/u/jbudd)\
**Post date:** [8 January 2023 02:07 UTC](https://discourse.nodered.org/t/logic-controlling-ventilation/73355/3 "2023-01-08T02:07:12Z")

</div>

It is possible using just core nodes and a context variable, perhaps a bit complicated.

 ![Untitled 3](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/b/5/b55b98b6a25ed3678854cec81558b1793c7e9ca0.jpeg)

```auto
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```

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<div class="post-metadata">

**Author:** ![FSHelgeland](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/fshelgeland/32/64260_2.png) [@FSHelgeland](https://discourse.nodered.org/u/FSHelgeland)\
**Post date:** [8 January 2023 15:24 UTC](https://discourse.nodered.org/t/logic-controlling-ventilation/73355/4 "2023-01-08T15:24:23Z")

</div>

I have had a look on the ultimate boolean logic node. But I was more thinking in a solution closer to the one jbudd have suggested here. I have already started building it, so I am going to test this one.

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [9 March 2023 15:24 UTC](https://discourse.nodered.org/t/logic-controlling-ventilation/73355/5 "2023-03-09T15:24:58Z")

</div>

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