# S7 control how does it works?

**URL:** <https://discourse.nodered.org/t/s7-control-how-does-it-works/51333>\
**Category:** Industrial\
**Created:** [21 September 2021 11:27 UTC](https://discourse.nodered.org/t/s7-control-how-does-it-works/51333 "2021-09-21T11:27:47Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Giu-seppe](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/giu-seppe/32/40489_2.png) [@Giu-seppe](https://discourse.nodered.org/u/Giu-seppe)\
**Post date:** [21 September 2021 11:27 UTC](https://discourse.nodered.org/t/s7-control-how-does-it-works/51333/1 "2021-09-21T11:27:47Z")

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Can some one give me an example of how works the node s7 control?  
I have read the documentation but I still don't understand how to use it, for a while it worked but now it doesn't work anymore.  
This is my use case

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/3/e/3e03c84d6e864193154cc52ce64cd01bc7594047.png)

EDIT: I need to read the variables only on trig

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**Author:** ![machadotiago](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/machadotiago/32/23776_2.png) [@machadotiago](https://discourse.nodered.org/u/machadotiago)\
**Post date:** [30 September 2021 21:48 UTC](https://discourse.nodered.org/t/s7-control-how-does-it-works/51333/2 "2021-09-30T21:48:15Z")

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Which kind of errors are you getting on your debug window?

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**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [29 November 2021 21:48 UTC](https://discourse.nodered.org/t/s7-control-how-does-it-works/51333/3 "2021-11-29T21:48:58Z")

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