Capacitive Rainmeter Measures The Sky Water Just Fine

November 28, 2023 by Lewin Day 15 Comments

If you’ve got a smart home, or you just want to know how soaked your garden is getting in the winter, you might want to measure rainfall. There are a bunch of ways to go about it, and this capacitive rainmeter solution from [Magnus Thome] might just be the perfect solution you’re looking for.

Like many who came before, [Magnus] had experimented with traditional resistive-based sensors using copper traces to measure water levels. As the soil moisture measuring set learned as well, corrosion tends to promise a pretty short life for these designs. Capacitive sensors, on the other hand, can be isolated from the water itself, and thus sense the levels without being subject to such degradation.

[Magnus] pairs the off-the-shelf capacitive sensor with an ESP32 charged with reading it and reporting back to Home Assistant. It’s also outfitted with a heater to keep it at a constant temperature to avoid it freezing over during those cold and snowy Swedish winters.

It’s a tidy way to integrate a quality commercial sensor with a DIY smart home setup. If you’ve been whipping up your own neat sensor networks for your smart home, don’t hesitate to let us know. Video after the break.

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Comparing Cheap Capacitative Soil Moisture Sensors With Commercial Sensors

February 1, 2023 by Maya Posch 40 Comments

When your residence has soil moisture sensors embedded that were dictated by your friendly neighborhood HoA, you may start asking questions about the system used. That’s what [Modest Maker] did and the resulting findings along with an attempt to beat the commercial system with some cheap capacitive sensors, are covered in a recent video that’s also embedded below. Part of the motivation here was that the commercial system in the community was not clearly installed properly.

To make a long story short, the commercial system by Hunter (Soil-Clik) appears to be a tensiometer-based system that uses the pressure produced by moisture intrusion into the measurement column. This translates to how easy it is for plant roots to extract water, depending on the soil type. [Modest Maker] had to first dodge the broken-by-design capacitive sensors that are available everywhere, but after that was able to cobble together a measurement system that he hopes will allow him to validate the commercial system’s installation.

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A soil moisture sensor with silkscreen chipped and copper corroded

Soil Moisture Sensor Coating Lessons Learned The Hard Way

March 2, 2022 by Arya Voronova 35 Comments

Ever wanted to measure soil moisture? Common “soil moisture meter module arduino raspberry compatible free shipping” PCBs might deceive you with their ascetic looks. Today, [Raphael (@rbaron_)] is here to teach us (Twitter, unrolled) what it takes to build a soil-embedded sensor that can actually survive contact with a plant.

As the picture might hint, waterproofing is of paramount importance, and soldermask doesn’t quite cut it. Raphael describes his journey of figuring out approaches and coatings that would last, starting from simply using nail polish, and ending with the current option – a rotisserie-like device that rotates sensors as the coating applied to them dries, mitigating a certain kind of structural failure observed long-term. With plenty of illustrative pictures and even a video of the rotisserie device in action, you’ll quickly learn things that took time and effort for Raphael to figure out.

This isn’t the first time Raphael shares some design battlefield stories and lessons with us – he has taught us about overall capacitive moisture sensor principles, too! If that interests you, we’ve covered quite a few moisture sensor designs, from cheap but hardy two-nails designs to flip-dot-equipped ones, and some of us take the commercial designs and upgrade them!

We thank [Chaos] for sharing this with us!

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Soil Moisture Sensors, How Do They Work?

May 17, 2021 by Donald Papp 19 Comments

In a way, the magic of a soil moisture sensor’s functionality boils down to a simple RC circuit. But of course, in practice there is a bit more to it than that. [rbaron] explains exactly how capacitive soil moisture sensors work simply, clearly, and concisely. He also shows, with a short video, exactly how their output changes in response to their environment, and explains how it informed his own sensor design.

At its heart, a moisture sensor measures how quickly (or slowly) a capacitor charges through a resistor, but in these sensors the capacitor is not a literal component, but is formed by two PCB traces that are near one another. Their capacitance — and therefore their charging rate — changes in response to how much water is around them. By measuring this effect on a probe sunk into dirt, the sensor can therefore indirectly measure the amount of water in the soil.

This ties into his own work on b-parasite: an open-source, all-in-one wireless soil moisture sensor (which was also a runner-up in our Earth Day contest) that broadcasts over BLE and even includes temperature readings. One thing to be mindful of if you are making your own PCBs or ordering them from a fab house is that passing current through metal in a moist environment is a recipe for oxidation, so it’s important not to expose bare traces to wet soil. A good coated PCB should avoid this problem, but one alternative we have seen proposed is to use graphite rods in place of metal.

Parts of the automated soil moisture monitoring station

Solar Stevenson Screen For Smart Sprinkler

April 11, 2021 by Bob Baddeley 1 Comment

It’s not infrequent that we see the combination of moisture sensors and water pumps to automate plant maintenance. Each one has a unique take on the idea, though, and solves problems in ways that could be useful for other applications as well. [Emiliano Valencia] approached the project with a few notable technologies worth gleaning, and did a nice writeup of his “Autonomous Solar Powered Irrigation Monitoring Station” (named Steve Waters as less of a mouthful).

Of particular interest was [Emiliano]’s solution for 3D printing a threaded rod; lay it flat and shave off the top and bottom. You didn’t need the whole thread anyway, did you? Despite the relatively limited number of GPIO pins on the ESP8266, the station has three analog sensors via an ADS1115 ADC to I2C, a BME280 for temperature, pressure, and humidity (also on the I2C bus), and two MOSFETs for controlling valves. For power, a solar cell on top of the enclosure charges an 18650 cell. Communication over wireless goes to Thingspeak, where a nice dashboard displays everything you could want. The whole idea of the Stevenson Screen is clever as well, and while this one is 3D printed, it seems any kind of stacking container could be modified to serve the same purpose and achieve any size by stacking more units. We’re skeptical about bugs getting in the electronics, though.

We recently saw an ESP32-based capacitive moisture sensor on a single PCB sending via MQTT, and we’ve seen [Emiliano] produce other high quality content etching PCBs with a vinyl cutter.

Give Your Smart Home A Green Thumb With MQTT

March 7, 2021 by Michael Shaub 36 Comments

We have all been stuck inside for too long, and maybe that’s why we have recently seen a number of projects attempting to help humans take better care of their housemates from Kingdom Plantae. To survive, plants need nutrients, light, and water. That last one seems tricky to get right; not too dry and not drowning them either, so [rbaron’s] green solder-masked w-parasite wireless soil monitor turns this responsibility over to your existing home automation system.

Like this low-power soil sensor project and the custom controller for six soil sensors, [rbaron’s] w-parasite uses a “parasitic capacitive” moisture sensor to determine if it’s time to water plants. This means that unlike resistive soil moisture sensors, here the copper traces are protected from corrosion by the solder mask. For those wondering how they work, [rbaron]’s Twitter thread has a great explanation.

The “w” in the name is for WiFi as the built-in ESP-32 module then takes the moisture reading and sends an update wirelessly via MQTT. Depending on the IQ of your smart-home setup, you could log the data, route an alert to a cellphone, light up a smart-bulb, or even switch on an irrigation system.

[rbaron] has shared a string of wireless hacks, controlling the A/C over Slack and a BLE Fitness Tracker that inspired more soldering than jogging. We like how streamlined this solution is, with the sensor, ESP-32 module, and battery all in a compact single board design. Are you asking yourself, “but how is a power-hungry ESP-32 going to last longer than it takes for my geraniums to dry out?” [rbaron] is using deep sleep that only consumes 15uA between very quick 500ms check-ins. The rechargeable LIR2450 Li-Ion coin cell shown here can transmit a reading every half hour for 90 days. If you need something that lasts longer than that, use [rbaron]’s handy spreadsheet to choose larger batteries that last a whole year. Though, let’s hope we don’t have to spend another whole year inside with our plant friends.

We may never know why the weeds in the cracks of city streets do better than our houseplants, but hopefully, we can keep our green roommates alive (slightly longer) with a little digital nudge.

This Negative Reinforcement Keyboard May Shock You

January 28, 2021 by Kristina Panos 23 Comments

We wouldn’t be where we are today without Mrs. Coldiron’s middle school typing class. Even though she may have wanted to, she never did use negative reinforcement to improve our typing speed or technique. We unruly teenagers might have learned to type a lot faster if those IBM Selectrics had been wired up for discipline like [3DPrintedLife]’s terrifying, tingle-inducing typist trainer keyboard (YouTube, embedded below).

This keyboard uses capsense modules and a neural network to detect whether the user is touch-typing or just hunting and pecking. If you’re doing it wrong, you’ll get a shock from the guts of a prank shock pen every time you peck the T or Y keys. Oh, and just for fun, there’s a 20 V LED bar across the top that is supposed to deter you from looking down at your hands with randomized and blindingly bright strobing light.

Twenty-four of the keys are connected in groups of three by finger usage — for example Q, A, and Z are wired to the same capsense module. These are all wired up to a Raspberry Pi Zero along with the light bar. [3DPrintedLife] was getting a lot of cross-talk between capsense modules, so they solved the problem in software by training a TensorFlow model with a ton of both proper and improper typing data.

We love the little meter on the touchscreen that shows at a glance how you’re doing in the touch typing department. As the meter inches leftward, you know you’re in for a shock. [3DPrintedLife] even built in some games that use pain to promote faster and more accurate typing. Check out the build video after the break, but don’t say we didn’t warn you about the strobing lights.

The secret to the shock pen is a tiny flyback transformer like the kind used in CRT televisions. Find a full-sized flyback transformer and you can build yourself a handheld high-voltage power supply.

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