# Getting I/O signals from old machines to communicate with Node-RED

**URL:** <https://discourse.nodered.org/t/getting-i-o-signals-from-old-machines-to-communicate-with-node-red/100273>\
**Category:** Industrial\
**Created:** [29 January 2026 16:16 UTC](https://discourse.nodered.org/t/getting-i-o-signals-from-old-machines-to-communicate-with-node-red/100273 "2026-01-29T16:16:30Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![Elindo586](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/elindo586/32/105439_2.png) [@Elindo586](https://discourse.nodered.org/u/Elindo586)\
**Post date:** [29 January 2026 16:16 UTC](https://discourse.nodered.org/t/getting-i-o-signals-from-old-machines-to-communicate-with-node-red/100273/1 "2026-01-29T16:16:30Z")

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In another post I asked about how to convert different different voltages into useful voltage that can be fed into a rasberrypi gpio's..

Is there anything that could transmit on/off signals via MQTT to use as an I/Os without the hardwire?..

I am not looking for a PLC, but is there something less expensive that could do the work so that we can get a signal and be able to write some Node-RED logics using the I/Os?

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**Author:** ![Aaqu](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/aaqu/32/101407_2.png) [@Aaqu](https://discourse.nodered.org/u/Aaqu)\
**Post date:** [29 January 2026 17:11 UTC](https://discourse.nodered.org/t/getting-i-o-signals-from-old-machines-to-communicate-with-node-red/100273/2 "2026-01-29T17:11:29Z")

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maybe something from waveshare, but you have to write the mqtt support yourself  
8in 8out ~ 50$

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/c/d/cd22e2511f25bb29212e58f147ff3dfb62c26e25.jpeg)

> **[Industrial 8-Channel ESP32-S3 WiFi Relay Module, Onboard isolated RS485...](https://www.waveshare.com/esp32-s3-eth-8di-8ro.htm)**
>
> Industrial 8-Channel ESP32-S3 WiFi Relay Module, Onboard isolated RS485 interface, Built-in Xtensa 32-bit LX7 Dual-core Processor, With Multiple Isolation Protection Circuits | ESP32-S3-ETH-8DI-8RO

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**Author:** ![Elindo586](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/elindo586/32/105439_2.png) [@Elindo586](https://discourse.nodered.org/u/Elindo586)\
**Post date:** [29 January 2026 17:13 UTC](https://discourse.nodered.org/t/getting-i-o-signals-from-old-machines-to-communicate-with-node-red/100273/3 "2026-01-29T17:13:43Z")

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Thank you!

Always fun to discover new toys 🙂

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**Author:** ![Sean-McG](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/sean-mcg/32/54677_2.png) [@Sean-McG](https://discourse.nodered.org/u/Sean-McG)\
**Post date:** [29 January 2026 17:16 UTC](https://discourse.nodered.org/t/getting-i-o-signals-from-old-machines-to-communicate-with-node-red/100273/4 "2026-01-29T17:16:22Z")

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You can use an ESP flashed with something like Tasmota to send MQTT messages on GPIO changes.

How to convert really depends on the voltages.

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**Author:** ![jbudd](https://avatars.discourse-cdn.com/v4/letter/j/5f8ce5/32.png) [@jbudd](https://discourse.nodered.org/u/jbudd)\
**Post date:** [29 January 2026 17:23 UTC](https://discourse.nodered.org/t/getting-i-o-signals-from-old-machines-to-communicate-with-node-red/100273/5 "2026-01-29T17:23:13Z")

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I do exactly this to monitor my pre-internet espresso machine.  
It does involve a PLC though and it's not especially cheap at c £12 per machine

I supply mains power to the espresso machine via a power monitoring smart socket which runs Tasmota.

The socket sends a message via MQTT when it is switched on or off, which I can do from Node-red, then I can interrogate it, also over MQTT, to obtain for example :

```auto
{
"Today":0.002, // Watt hours (since the power cut earlier)
"Power":756, // Watts
"ApparentPower":756,
"ReactivePower":0,
"Factor":1,
"Voltage":196, // Either it's a major brown-out or I need to recalibrate the smart socket
"Current":3.849 // Amps
}

```

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<div class="post-metadata">

**Author:** ![DWoodlock](https://avatars.discourse-cdn.com/v4/letter/d/49beb7/32.png) [@DWoodlock](https://discourse.nodered.org/u/DWoodlock)\
**Post date:** [13 February 2026 13:25 UTC](https://discourse.nodered.org/t/getting-i-o-signals-from-old-machines-to-communicate-with-node-red/100273/6 "2026-02-13T13:25:56Z")

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I guess it depends what you consider expensive?

I was recently researching this for getting data from some chillers, and it ended up the cheapest and easiest was to use a click plc, but tha may be more than you wanted to spend although it’s considered cheap for industrial applications.

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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:** [14 April 2026 13:26 UTC](https://discourse.nodered.org/t/getting-i-o-signals-from-old-machines-to-communicate-with-node-red/100273/7 "2026-04-14T13:26:42Z")

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