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Joined: Thu Sep 05, 2019 6:16 pm

Terrarium mister wiring diagram

Thu Sep 05, 2019 6:34 pm


I have an automatic misting project for a vivarium that I've been working towards, and I'd like some input on the wiring diagram I have for the project. I have the Pi's GPIO pins hooked up to a breadboard via a ribbon cable. There is a temp/humidity sensor hooked up to the board and a power switch relay hooked up to the board. I plan on reading the humidity from the sensor and subsequently turning the mister on if the humidity is below a certain threshold.

I made this diagram based on some preliminary internet searches about examples, code from similar projects, and the sensor and device documentation. At this point though I don't have enough experience to even ask a specific enough question about the wiring diagram I have. Therefor I am looking for some general feedback about its functionality, improper configuration, etc.

Thank you for any input you can provide,

wiring diagram draft
VivariumMister.jpg (85.54 KiB) Viewed 340 times

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Joined: Fri May 31, 2013 9:28 pm
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Re: Terrarium mister wiring diagram

Fri Sep 06, 2019 10:43 am


First off you should not be using 5v to power either device if they are directly connected to the pi gpio pins , the gpio is not 5v tolerant and applying 5v to it will kill your pi.

If you want help connecting your devices we need to know exactly what they are .

So model number and a link to were you got them is always a good starting point.
We want information… information… information no help
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Joined: Wed Jun 20, 2012 2:51 pm
Location: Southampton, England

Re: Terrarium mister wiring diagram

Mon Sep 09, 2019 7:43 am

The DHT11 or 22 sensors will run from 3V3. This way you will not fry your GPIO input port with the signal return. Most tutorials (e.g. ... pberry-pi/) include a 10K pull up resistor between data and V+, although you might get away with using the internal pull up.

You are probably better using a dedicated relay control board that you just need to send a control signal to, rather than trying to power the coil from a GPIO pin. At the minimum look up about flyback diodes, or you risk frying another pin. Watch out with cheap relay boards that they do not just do what you have on your original circuit, although normally with flyback diodes in place. Very few relays on these budget boards have a coil that operates below a nomimal 5V, which means a limit of about 3.8V in practice. The 3.3V from the GPIO is not high enough, and the pin output current limit (25mA?) might not be enough to drive some coils either.
If you look at something like ... ifications you can see from the schematic that is it uses 3.3v control signals, protects the GPIOs with opto-couplers, and uses the 5V connection to drive the coils. (Disclaimer - I have not used this specific board)

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