When you see a project with a digital display these days, you’ll be forgiven for assuming that there’s some kind of microcontroller behind the scenes. And while that’s often the easiest way to get a project from idea to completion, it’s rarely the most interesting way.
This digital pH meter is a great example of that “no-code” design philosophy. According to [chris], the main use for this meter will be to measure soil pH in his garden, and the reason for eschewing a microcontroller was more or less for the challenge. And quite a challenge it was. Understanding the concept of pH isn’t always easy, and many a budding chemist has fallen victim to its perils. Actually measuring pH isn’t much easier, with the need to account for a lot of variables while measuring small voltages. Adding to the challenge was the fact that pretty much every skill on display here — from using KiCad to SMD soldering — was the first time [chris] had tackled them.
To amplify the voltage from the off-the-shelf pH probe, [chris] chose an LMV358A, a high-impedance FET-input version of the venerable LM358 op-amp, so as not to load down the probe. A negative temperature coefficient (NTC) resistor in the feedback path provides temperature compensation. He also designed a split power supply to provide positive and negative rails from a single 9-volt battery. The 3.5-digit LCD display is driven by an ICL7106 integrated A/D converter and BCD driver chip. Everything went into a nice-looking plastic enclosure that’s very suitable for a portable instrument.
As of this writing, the Op-Amp Challenge has officially wrapped, and there’s a slew of last-minute entries we need to go through. Check out the competition and stay tuned to find out who the judges pick for op-amp design glory!
While it can be straightforward to distill water to high purity, this is rarely the best method for producing water for useful purposes. Even drinking water typically needs certain minerals in it, plants may need a certain pH, and wastewater systems have a whole host of other qualities that need to be measured. Measuring water quality is a surprisingly complex endeavor as a result and often involves a wide array of sensors, much like this water quality meter from [RowlesGroupResearch].
The water quality meters that they are putting to use are typically set up in remote locations, without power, and are targeting natural bodies of water and also wastewater treatment plants. Temperature and pH are simple enough to measure and grasp, but this device also includes sensors for total dissolved solids (TDS) and turbidity which are both methods for measuring various amounts and types of particles suspended in the water. The build is based around an Arduino so that it is easy for others to replicate, and is housed in a waterproof box with a large battery, and includes data logging to an SD card in order to make it easy to deploy in remote, outdoor settings and to gather the data at a later time.
The build log for this device also goes into detail about all of the steps needed to set this up from scratch, as well as a comprehensive bill of materials. This could be useful in plenty of professional settings such as community wastewater treatment facilities but also in situations where it’s believed that industrial activity may be impacting a natural body of water. For a water quality meter more focused on drinking water, though, we’d recommend this build that is trained on its own neural network.
If you’ve ever had surgery, you know firsthand how important it is to keep the wound from getting infected. There are special conductive sutures that sense changes in wound status via electrical signal and relay the information to a computer or smart phone. As awesome as those sound, they’re a first-world solution that is far too pricey for places that need it most — developing countries. And surgical wounds in developing countries are about four times more likely to get infected than those in the US.
Beets, and other fruits and vegetables like blackberries, plums, and blueberries are natural indicators of pH. They have a compound called anthocyanin that gives them both their pigment and this cool property. Beets are perfect because they change color at a pH of nine — the same pH level of infected human skin, which is normally around five.
[Dasia] experimented with several types of suture thread to see which ones would absorb the beet juice in the first place. She settled on a cotton-polyester blend that is braided. While it probably helps absorb the beet juice, it would also give bacteria several places to hide. Another problem is that many surgeries involve cutting muscle, too, and by the time a deeper infection would show up on the sutures, it would be pretty late in the game. But if these color-changing sutures can be made to be cost-effective, safe for skin, and of course, keep wounds together, this solution is way better than nothing at all and definitely worth producing. You can see [Dasia] talk about her project in the video below.
Want to know more about natural pH indicators? Sure you do.
Automation is a lofty goal in many industries, but not always straightforward to execute. Welding car bodies in the controlled environment of a production line is relatively straightforward. Maintaining plants in a greenhouse, however, brings certain complexities due to the unpredictable organic processes at play. Hexagrow is a robot that aims to study automation in this area, developed as the final year project of [Mithira Udugama] and team.
The robot’s chassis is a very modern build, consisting of carbon fiber panels and 3D printed components. This kind of strength is perhaps overkill for the application, but it makes for a very light and rigid robot when the materials are used correctly.
It’s the sensor package where this build really shines, however. There’s the usual accoutrement of temperature and humidity sensors, and a soil moisture probe, as we’d expect. But there’s more, including an impressive soil pH tester. This involves a robotic arm with a scoop to collect soil samples, which are then weighed by a load cell. This is then used to determine the correct amount of water to add to the sample. The mixture is then agitated, before being tested by the probe to determine the pH level. It recalls memories of the science packages on Mars rovers, and it’s great to see this level of sophistication in a university project build. There’s even a LIDAR mounted on top for navigation purposes, though it’s not clear as to whether this sensor is actually functionally used at this point in development.
Anyone who owns their own pool knows it’s not as simple as filling it up with water and jumping in whenever you want. There’s pool covers to deal with, regular cleaning with the pool vacuum and skimmers, and of course, all of the chemicals that have to be added to keep the water safe. While there are automatic vacuums, there aren’t a whole lot of options for automating the pool chemicals. [Clément] decided to tackle this problem, eliminating one more task from the maintenance of his home. (Google Translate from French.)
The problem isn’t as simple as adding a set amount of chemicals at a predetermined time. The amount of chemicals that a pool owner has to add are dependent on the properties of the water, and the amount of time that’s elapsed since the previous chemical treatment, and the number of people who have been using the water, and whether or not the pool cover is in use. To manage all of this, [Clément] used an ORP/Redox probe and a pH probe, and installed both in the filtration system. The two probes are wired to an Arduino with an ethernet shield. The Arduino controls electrically actuated chemical delivery systems that apply the required amount of chemicals to the pool, keeping it at a nice, healthy balance. Continue reading “Home Pool Added To Home Automation”→
Scientific research, especially in the area of robotics, often leverages cutting-edge technology. Labs filled with the latest measurement and fabrication gear are unleashed on the really tough problems, like how to simulate the exquisite sensing abilities of human skin. One lab doing work in this area has taken a different approach, though, by building multi-functional sensors arrays from paper.
A group from the King Abdullah University of Science and Technology in Saudi Arabia, led by [Muhammad M. Hussain], has published a fascinating paper that’s a tour de force of getting a lot done with nothing. Common household items, like Post-It notes, kitchen sponges, tissue paper, and tin foil, are used to form the basis of what they call “paper skin”. Fabrication techniques – scissors and tape – are ridiculously simple and accessible to anyone who made it through kindergarten.
They do turn to a Circuit Scribe pen for some of their sensors, but even this nod to high technology is well within their stated goal of making it possible for anyone to fabricate sensors at home. The paper goes into great detail about how the sensors are made, how they interact, and how they are interfaced. It’s worth a read to see what you can accomplish with scraps.
Laying hands on the supplies for most hacks we cover is getting easier by the day. A few pecks at the keyboard and half a dozen boards or chips are on an ePacket from China to your doorstep for next to nothing. But if hacking life is what you’re into, you’ll spend a lot of time and money gathering the necessary instrumentation. Unless you roll your own mini genetic engineering lab from scratch, that is.
Taking the form of an Arduino mega-shield that supports a pH meter, a spectrophotometer, and a PID-controlled hot plate, [M. Bindhammer]’s design has a nice cross-section of the instruments needed to start biohacking in your basement. Since the shield piggybacks on an Arduino, all the data can be logged, and decisions can be made based on the data as it is collected. One example is changing the temperature of the hot plate when a certain pH is reached. Not having to babysit your experiments could be a huge boon to the basement biohacker.