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An engineer’s dinner-table invention is finally a consumer product

For Evan Schneider, the family dinner table is a good place for invention. “I’m always, ‘Wouldn’t it be cool if this or that,’” he says, “and people would humor me.”

In 2012, with California in the midst of a severe drought, Schneider, then a mechanical engineering graduate student at Stanford University, once again tossed out a “cool idea.” He imagined a showerhead that would sense when the person showering moved out from under the stream of water. The showerhead would then automatically turn the water off, turning it back on again when the person moved back into range. With such a device, he thought, people could enjoy a long shower without wasting water.

“But turning the water on and off manually didn’t make sense in our house,” Schneider said. “We had separate knobs for hot and cold, and another one to switch from tub to shower, so you’d have to adjust the water every time you turned it back on. You’d waste more water than you saved. Plus a shower is a blissful time of relaxation. You don’t want to stop the party halfway.”

Ten years and many starts and stops later, that sensing showerhead is now shipping to customers from Oasense, a company incorporated in 2019.

“The general idea is really simple,” Schneider says. “A lot of people have said they also thought of this idea. And I’m sure that’s true, but there were a lot of devils in the details.” Oasense’s team has been granted several patents related to their device, the first filed by Schneider in 2016.

Schneider’s development path started soon after that dinner-table conversation. First, he confirmed that showers were a big part of water usage for a typical household, and that no such device was already on the market. He collected off-the-shelf components, including an infrared sensor scavenged from a high-end automatic faucet, designed a prototype in a CAD system, printed out the plastic parts using a 3D printer, and assembled it. With 4 AA batteries as a power source, the gadget would operate for about a year, thanks to his choice of a latching solenoid valve, one that uses power to switch from open to closed but doesn’t draw any power to hold in one state or another.

The prototype worked well enough that his parents were willing to throw out their standard showerhead. He assembled dozens of them and distributed them to friends and family—anyone willing to try.

Oasense cofounder Ted Li assembles an early version of the company’s sensing showerhead.Oasense

In 2016, Schneider decided to run a Kickstarter campaign to see if the gadget could attract broad interest. The Kickstarter ultimately failed; it drew a decent number of potential buyers, but, says Schneider, “I had set the bar high, because I was busy doing other things, and if I switched to this, I wanted to make sure it would have a good chance of working out. It didn’t meet that bar; it raised about US $34,000 out of its $75,000 goal.”

So Schneider put his showerhead idea on hold. Instead, he focused on expanding a burgeoning small business that he was also passionate about—3D printing prototypes and various parts for hardware companies.

But the showerhead wasn’t done with him. In 2017 someone who Schneider had never met edited the video from the Kickstarter pitch and shared it on Facebook. This time, the video got far more attention—millions of views in just weeks.

Unfortunately, the timing couldn’t have been worse. Schneider was dealing with a flare-up of a chronic illness and his 3D printing business was at a critical growth period. “I had wanted this for years, but it was the worst time for it to happen,” he says.

“I still believed in the product,” Schneider continued, “but I knew it needed improvements and more attention than I was able to give it. I tried for a couple of weeks to reply to all these people contacting me, thousands of them, but it was too much. I was planning to shelve it.”

That’s when Chih-Wei Tang, a friend from Stanford’s mechatronics program who had been an early backer of the project on Kickstarter, reached out to Schneider. Tang, who was working as a technical product manager at the Ford Greenfield Labs, convinced Schneider that he could form a team capable of commercializing the product. Tang pulled in his friend Ted Li, who had just left Apple after managing display technology for the iPhone and Apple Watch.

Tang and Li devoted themselves to the project full-time, Schneider helped part-time as needed. The three started by trying to better adapt an off-the-shelf sensor, but ended up designing a sensor suite with custom hardware and algorithms.

They incorporated as Oasense in December 2019 as cofounders. In late 2020, the company went out for funding, and brought in about $1 million from angel investors, friends, and family. In addition to the founders, Oasense now has four full-time and three part-time employees.

Oasense cofounders [from left] Ted Li, Evan Schneider, and Chih-Wei Tang.Oasense

The current version of the device includes several sensors (across a wide range of light wavelengths) and software that allows the sensors to self-calibrate, since every shower environment is different in terms of light, reflectivity, size, and design. Calibration happens during warm-up, when the person showering is unlikely to be standing in the stream. A temperature sensor determines when this warm-up period is over and cuts the flow if the user hasn’t moved under the showerhead. The redesign also replaced the AA batteries with a turbine that generates power from the water flow and sends it to a small rechargeable battery sealed inside the device.

Says Tang, “It does seem like someone would have built this before, but it turns out to be really complicated. For example, one problem that affects the noise in the sensor signals is fog. In a hot shower, after 3 minutes, our original sensor was blinded by fog. When we designed our new sensors, we had to make sure that didn’t happen.

“And these sensors are power hungry and need to be on for the duration of the shower, whether water is flowing or not, so generator and sensor efficiency had to be maximized.”

Oasense officially launched its product, Reva, in August. The company is working to figure out the best way to sell the gadget; it is now just doing direct sales at $350 per self-installable unit.

“Two trends are coming together,” Tang says. “Sustainability is what everyone has to be about these days, and technology is invading every corner of our homes. Using technology, we designed sustainability into a product that doesn’t compromise quality or the experience, it just addresses the problem.”

Tekla S. Perry is a senior editor at IEEE Spectrum. Based in Palo Alto, Calif., she's been covering the people, companies, and technology that make Silicon Valley a special place for more than 40 years. An IEEE member, she holds a bachelor's degree in journalism from Michigan State University.

I’ve been using this shower head for months and have saved a lot of water. I’m glad to see it getting more exposure.

Interesting and clever ... but it's impossible to evaluate the overall effectiveness of this device without knowing how much water it uses while on. There are substantial differences between conventional shower heads in water consumption.

Open Circuits showcases the surprising complexity of passive components

Eric Schlaepfer was trying to fix a broken piece of test equipment when he came across the cause of the problem—a troubled tantalum capacitor. The component had somehow shorted out, and he wanted to know why. So he polished it down for a look inside. He never found the source of the short, but he and his collaborator, Windell H. Oskay, discovered something even better: a breathtaking hidden world inside electronics. What followed were hours and hours of polishing, cleaning, and photography that resulted in Open Circuits: The Inner Beauty of Electronic Components (No Starch Press, 2022), an excerpt of which follows. As the authors write, everything about these components is deliberately designed to meet specific technical needs, but that design leads to “accidental beauty: the emergent aesthetics of things you were never expected to see.” From a book that spans the wide world of electronics, what we at IEEE Spectrum found surprisingly compelling were the insides of things we don’t spend much time thinking about, passive components. Transistors, LEDs, and other semiconductors may be where the action is, but the simple physics of resistors, capacitors, and inductors have their own sort of splendor. High-Stability Film Resistor All photos by Eric Schlaepfer & Windell H. Oskay This high-stability film resistor, about 4 millimeters in diameter, is made in much the same way as its inexpensive carbon-film cousin, but with exacting precision. A ceramic rod is coated with a fine layer of resistive film (thin metal, metal oxide, or carbon) and then a perfectly uniform helical groove is machined into the film. Instead of coating the resistor with an epoxy, it’s hermetically sealed in a lustrous little glass envelope. This makes the resistor more robust, ideal for specialized cases such as precision reference instrumentation, where long-term stability of the resistor is critical. The glass envelope provides better isolation against moisture and other environmental changes than standard coatings like epoxy. 15-Turn Trimmer Potentiometer It takes 15 rotations of an adjustment screw to move a 15-turn trimmer potentiometer from one end of its resistive range to the other. Circuits that need to be adjusted with fine resolution control use this type of trimmer pot instead of the single-turn variety. The resistive element in this trimmer is a strip of cermet—a composite of ceramic and metal—silk-screened on a white ceramic substrate. Screen-printed metal links each end of the strip to the connecting wires. It’s a flattened, linear version of the horseshoe-shaped resistive element in single-turn trimmers. Turning the adjustment screw moves a plastic slider along a track. The wiper is a spring finger, a spring-loaded metal contact, attached to the slider. It makes contact between a metal strip and the selected point on the strip of resistive film. Ceramic Disc Capacitor Capacitors are fundamental electronic components that store energy in the form of static electricity. They’re used in countless ways, including for bulk energy storage, to smooth out electronic signals, and as computer memory cells. The simplest capacitor consists of two parallel metal plates with a gap between them, but capacitors can take many forms so long as there are two conductive surfaces, called electrodes, separated by an insulator. A ceramic disc capacitor is a low-cost capacitor that is frequently found in appliances and toys. Its insulator is a ceramic disc, and its two parallel plates are extremely thin metal coatings that are evaporated or sputtered onto the disc’s outer surfaces. Connecting wires are attached using solder, and the whole assembly is dipped into a porous coating material that dries hard and protects the capacitor from damage. Film Capacitor Film capacitors are frequently found in high-quality audio equipment, such as headphone amplifiers, record players, graphic equalizers, and radio tuners. Their key feature is that the dielectric material is a plastic film, such as polyester or polypropylene. The metal electrodes of this film capacitor are vacuum-deposited on the surfaces of long strips of plastic film. After the leads are attached, the films are rolled up and dipped into an epoxy that binds the assembly together. Then the completed assembly is dipped in a tough outer coating and marked with its value. Other types of film capacitors are made by stacking flat layers of metallized plastic film, rather than rolling up layers of film. Dipped Tantalum Capacitor At the core of this capacitor is a porous pellet of tantalum metal. The pellet is made from tantalum powder and sintered, or compressed at a high temperature, into a dense, spongelike solid. Just like a kitchen sponge, the resulting pellet has a high surface area per unit volume. The pellet is then anodized, creating an insulating oxide layer with an equally high surface area. This process packs a lot of capacitance into a compact device, using spongelike geometry rather than the stacked or rolled layers that most other capacitors use. The device’s positive terminal, or anode, is connected directly to the tantalum metal. The negative terminal, or cathode, is formed by a thin layer of conductive manganese dioxide coating the pellet. Axial Inductor Inductors are fundamental electronic components that store energy in the form of a magnetic field. They’re used, for example, in some types of power supplies to convert between voltages by alternately storing and releasing energy. This energy-efficient design helps maximize the battery life of cellphones and other portable electronics. Inductors typically consist of a coil of insulated wire wrapped around a core of magnetic material like iron or ferrite, a ceramic filled with iron oxide. Current flowing around the core produces a magnetic field that acts as a sort of flywheel for current, smoothing out changes in the current as it flows through the inductor. This axial inductor has a number of turns of varnished copper wire wrapped around a ferrite form and soldered to copper leads on its two ends. It has several layers of protection: a clear varnish over the windings, a light-green coating around the solder joints, and a striking green outer coating to protect the whole component and provide a surface for the colorful stripes that indicate its inductance value. Power Supply Transformer This transformer has multiple sets of windings and is used in a power supply to create multiple output AC voltages from a single AC input such as a wall outlet. The small wires nearer the center are “high impedance” turns of magnet wire. These windings carry a higher voltage but a lower current. They’re protected by several layers of tape, a copper-foil electrostatic shield, and more tape. The outer “low impedance” windings are made with thicker insulated wire and fewer turns. They handle a lower voltage but a higher current. All of the windings are wrapped around a black plastic bobbin. Two pieces of ferrite ceramic are bonded together to form the magnetic core at the heart of the transformer.

Eric Schlaepfer was trying to fix a broken piece of test equipment when he came across the cause of the problem—a troubled tantalum capacitor. The component had somehow shorted out, and he wanted to know why. So he polished it down for a look inside. He never found the source of the short, but he and his collaborator, Windell H. Oskay, discovered something even better: a breathtaking hidden world inside electronics. What followed were hours and hours of polishing, cleaning, and photography that resulted in Open Circuits: The Inner Beauty of Electronic Components (No Starch Press, 2022), an excerpt of which follows. As the authors write, everything about these components is deliberately designed to meet specific technical needs, but that design leads to “accidental beauty: the emergent aesthetics of things you were never expected to see.”

From a book that spans the wide world of electronics, what we at IEEE Spectrum found surprisingly compelling were the insides of things we don’t spend much time thinking about, passive components. Transistors, LEDs, and other semiconductors may be where the action is, but the simple physics of resistors, capacitors, and inductors have their own sort of splendor.

All photos by Eric Schlaepfer & Windell H. Oskay

This high-stability film resistor, about 4 millimeters in diameter, is made in much the same way as its inexpensive carbon-film cousin, but with exacting precision. A ceramic rod is coated with a fine layer of resistive film (thin metal, metal oxide, or carbon) and then a perfectly uniform helical groove is machined into the film.

Instead of coating the resistor with an epoxy, it’s hermetically sealed in a lustrous little glass envelope. This makes the resistor more robust, ideal for specialized cases such as precision reference instrumentation, where long-term stability of the resistor is critical. The glass envelope provides better isolation against moisture and other environmental changes than standard coatings like epoxy.

It takes 15 rotations of an adjustment screw to move a 15-turn trimmer potentiometer from one end of its resistive range to the other. Circuits that need to be adjusted with fine resolution control use this type of trimmer pot instead of the single-turn variety.

The resistive element in this trimmer is a strip of cermet—a composite of ceramic and metal—silk-screened on a white ceramic substrate. Screen-printed metal links each end of the strip to the connecting wires. It’s a flattened, linear version of the horseshoe-shaped resistive element in single-turn trimmers.

Turning the adjustment screw moves a plastic slider along a track. The wiper is a spring finger, a spring-loaded metal contact, attached to the slider. It makes contact between a metal strip and the selected point on the strip of resistive film.

Capacitors are fundamental electronic components that store energy in the form of static electricity. They’re used in countless ways, including for bulk energy storage, to smooth out electronic signals, and as computer memory cells. The simplest capacitor consists of two parallel metal plates with a gap between them, but capacitors can take many forms so long as there are two conductive surfaces, called electrodes, separated by an insulator.

A ceramic disc capacitor is a low-cost capacitor that is frequently found in appliances and toys. Its insulator is a ceramic disc, and its two parallel plates are extremely thin metal coatings that are evaporated or sputtered onto the disc’s outer surfaces. Connecting wires are attached using solder, and the whole assembly is dipped into a porous coating material that dries hard and protects the capacitor from damage.

Film capacitors are frequently found in high-quality audio equipment, such as headphone amplifiers, record players, graphic equalizers, and radio tuners. Their key feature is that the dielectric material is a plastic film, such as polyester or polypropylene.

The metal electrodes of this film capacitor are vacuum-deposited on the surfaces of long strips of plastic film. After the leads are attached, the films are rolled up and dipped into an epoxy that binds the assembly together. Then the completed assembly is dipped in a tough outer coating and marked with its value.

Other types of film capacitors are made by stacking flat layers of metallized plastic film, rather than rolling up layers of film.

At the core of this capacitor is a porous pellet of tantalum metal. The pellet is made from tantalum powder and sintered, or compressed at a high temperature, into a dense, spongelike solid.

Just like a kitchen sponge, the resulting pellet has a high surface area per unit volume. The pellet is then anodized, creating an insulating oxide layer with an equally high surface area. This process packs a lot of capacitance into a compact device, using spongelike geometry rather than the stacked or rolled layers that most other capacitors use.

The device’s positive terminal, or anode, is connected directly to the tantalum metal. The negative terminal, or cathode, is formed by a thin layer of conductive manganese dioxide coating the pellet.

Inductors are fundamental electronic components that store energy in the form of a magnetic field. They’re used, for example, in some types of power supplies to convert between voltages by alternately storing and releasing energy. This energy-efficient design helps maximize the battery life of cellphones and other portable electronics.

Inductors typically consist of a coil of insulated wire wrapped around a core of magnetic material like iron or ferrite, a ceramic filled with iron oxide. Current flowing around the core produces a magnetic field that acts as a sort of flywheel for current, smoothing out changes in the current as it flows through the inductor.

This axial inductor has a number of turns of varnished copper wire wrapped around a ferrite form and soldered to copper leads on its two ends. It has several layers of protection: a clear varnish over the windings, a light-green coating around the solder joints, and a striking green outer coating to protect the whole component and provide a surface for the colorful stripes that indicate its inductance value.

This transformer has multiple sets of windings and is used in a power supply to create multiple output AC voltages from a single AC input such as a wall outlet.

The small wires nearer the center are “high impedance” turns of magnet wire. These windings carry a higher voltage but a lower current. They’re protected by several layers of tape, a copper-foil electrostatic shield, and more tape.

The outer “low impedance” windings are made with thicker insulated wire and fewer turns. They handle a lower voltage but a higher current.

All of the windings are wrapped around a black plastic bobbin. Two pieces of ferrite ceramic are bonded together to form the magnetic core at the heart of the transformer.

This article appears in the February 2023 print issue.