61 lines
3.3 KiB
Markdown
61 lines
3.3 KiB
Markdown
---
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title: "Sensors&Pumps"
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date: 2025-01-27
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draft: false
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description: "a description"
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tags: ["sensor"]
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---
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# Sensors
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The board can address up to 16 sensors, with an A und B sensor per plant.
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The A sensor is always used, the B sensor is optional and use is suggested for larger planters.
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The sensor itself are just two spikes with a defined distance. They can be bought readymade or simply be done DIY with two long nails (use galvanized or non rusting ones)
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The Sensor is switched via multiplexer chips to a 555 oscilator circuit that uses he the earths resistance for charging and discharging a small capacitor. The ESP simply counts how often the charge pulse was seen.
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While this sensor can be easily influenced since it runs in lower uA - mA range, due to the frequencys of several khz for normal moist plants, it is still very resistant, eg a 50hz failure signal from a nearbly power circuit would barely be registered.
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Since the Sensor is changing polarity between charging and discharging, corrosion due to organic battery effects is minimized, also it prevents errors due having build a battery (You can easily charge a planter to several V if you do not change polarity).
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# Pumps
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The board contains 8 low side switched pump outputs. The pumps are running directly from the battery without further voltage conversion, so ensure that the can survive the full voltage range of the battery.
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Each output can supply up to 3A continously.
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The board will never switch more than one output concurrently, so there is no need to size the battery for higher maximum load.
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An additinal extra out exists, that is switched, when any of the pump outputs is supposed to run.
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This allows for multiple possible setups
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## Layout Central Pump
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One central pump is connected to the extra output, and multiple magnetic valves are used for the different plants
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## Multi Gravity Feed Valves
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Per plant a Valve that can close against pressure is used, no pump exists
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## Multi Pump Setup
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Multiple smaller cheaper pumps with no shared hoses, so that failures will only affect a single planter.
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In any case I suggest to use a Water Filter on the Intake, as else you will get severe algae problems.
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In my personal opinion small membrane pumps are a really good fit
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* can be housed outside the tank
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* require less maintance/cleaning
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* are able to pump smaller impurities without issues.
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* Can pull water 1-2meters
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* Have higher output pressure -> Will blow out blockages in hoses
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However
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* are louder
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* pump less volume per time and energy
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{{< alert >}}
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DO NOT DIRECTLY CONNECT TO WATER MAINS, YOU HAVE BEEN WARNED!
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Software and Hardware may fail: It is your responsibility to ensure that a stuck valve or short circuit mosfet will not cause flooding and property destruction, for example by limiting the water tank to size that can drain.
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{{< /alert >}}
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# Todo
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## Flow Sensor
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There is a input for a flow sensor, currently it is not used as the software is missing.
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* Allow monitoring if pumps are actually moving water
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* Allow to set limits for how much ml are allowed additinally to the current time limit per watering run
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Currently it cannot be set how two sensor should be interpreted and they are only averaged. More complex functions would be nice here, eg. allowing a user settable interpolation (0.8*a+0.2*b)/2 and Min(a,b) as well as max(a,b)
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