Controlling a RaspberryPi GPIO pin with MQTT

Tutorials & Examples
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5

All connected to RPI gpio pins or just multiple MQTT messages?

6

Yes all on my rpi

And need to go to mqtt ?

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I want most of my sensors that do my enviro monitoring running of my rpi. And comunicate via mqtt. That i have in center of my house. My ligits runs off of sonnof t1
And my other power controls i use esp8266

8

Or Is there other suggestions on how to do this as the rip that the sensors are connected to is my openhab server aswell.

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Check out this link:

https://github.com/rkoshak/sensorReporter

10

perhaps I misunderstand the question, but it is just as always with mqtt, check for the incoming message and then take action on that basis.

The program I provided only checks on Payload ON/OF as I only control one pin and am subscribed to one topic, but if you want to control more pins, you also need to check on ‘Topic’’

So in my program, before the check:
if (msg.payload=='ON'):

you would first check which topic, like so:
if (msg.topic=='mytopic1'):

and then that is followed by the ON/OFF check

You repeat that for the amount of topics you are subscribed to.

so it would be:

check for topic 1
   if payload ==ON ->take action
   if payload==OFF -> take action

check for topic 2
   if payload ==ON ->take action
   if payload==OFF -> take action

etcetera

Now ofcourse if it is all on the same raspi as your openhab install, you do not need mqtt, then you just let openhab set the desired pins directly, via the GPIO binding, as I explained here:https://community.openhab.org/t/simple-gpio-example/36062?u=kees_van_gelder

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i was thinking if that would not be better doing it direct.
my other question is how would I do analog ?
I ill be using a map 3008 for to mq-05 gas sensors
and 7 x dht 22, and then only one relay that turns a extractor on and off in the bath room.

will draw out a diagram showing my idea and setup.

12

the raspi is not really great at doing analog signals, as it has no ADC, although it is possible to use an analog signal that charges a capacitor and then measure the time it takes to reach a certain voltage. But I wouldn’t advise to go that way.

I presume you mean the MCP3008, that is certainly an option. I think that one uses SPI. My preference would be an I2C module and there are plenty of those as well
the 7xdht22 can all be handled with the digital pins of the raspberry.Plenty of totorials available and I did one as well here on the forum Reading a DHT11/22 on a raspberry and send the results by MQTT

13

sorry about the typo.

I would also rather look at using the i2c.
the mQ-x range comes mostly with AQ. and only a few with DQ. the one I am looking at using is analog. for measuring LPG an Co2.in the kitchen and in the entertainment area .

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but I can also read the dht22 directly in openhab no need to use mqtt

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consider he ADS1115

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You could also use your esp8266, depending where you need the sensors, it has ADC ability. Heres example/guide on how to use:https://www.instructables.com/id/ESP8266-with-Multiple-Analog-Sensors/

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certainly a possibility
@allen
keep in mind the MQ-x sensors need preheating, though some are OK to just remain connected to Vcc, some others need a certain cycling of the applied voltage.Certainly the CO sensor needs that. Not sure about the MQ-5

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what other sensors would you recommend for the application ?

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well that all depends on what you like to measure.
depending on the purpose (like CO2 for plant growth) I would generally be more interested in CO levels.
LPG, I am not sure. I guess it will also react to the gas you might be cooking on in yr kitchen,

MQ-2 does methane and Butane, LPG and smoke
MQ-4 does methane and CNG
MQ-6 does butane and LPG
MQ-7 does CO
seems only the MQ7 needs to cycle between 5V and 1.4V.the others just need 5 or 6 v
Full summary here http://playground.arduino.cc/Main/MQGasSensors

20

I had a look at this now.

will get one and test. and see what happens. the co I might just leave
as long as I can read lpg and say smoke. like the mq-2

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good choice

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Thanks for the information and also the tutorials you guys do.
hope fully one day I will get to the point as well . I am still learning the system and all the finer details and working.

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thanks for your kind words. good luck and don’t hesitate to ask more questions if needed.
Once you finished your project, consider sharing it, it may help someone else

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I will share once I am done and running.

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