If you ever thought about becoming a treasure hunter this simple DIY metal detector by [mircemk] may be a nice project to start with.
The design is based on an opensource metal detector called Smart Hunter. This Very Low Frequency (VLF) metal detector uses transmitter and receiver coils in so-called Double-D geometry. The transmitter coil is driven by a signal generator module that operates at its resonant frequency of 4.74 kHz.
The resulting oscillating magnetic field will induce eddy currents in a nearby metal object that in turn induce a signal in the receiver coil. This signal is then fed into the microphone port of a smartphone and analyzed by a custom metal detector app. [mircemk] also included an audio amplifier and small speaker into the device.
The detector turned out to be quite sensitive and can detect a coin at up to 25 cm distance and larger metal objects even up to 1 m. Modern metal detectors can also distinguish between different types of metal by analyzing the phase shift of the detected signal which might be some way to improve the design.
Mobile phones are the photography tool for most of us, but they are a blunt tool. If you love astrophotography, you buy a DSLR and a lens adapter. Infrared photography needs camera surgery or a special unit. If you want to look closer to home, you may have a microscope with a CCD. Your pocket computer is not manufactured for microscopy, but that does not mean it cannot be convinced. Most of us have held our lens up to the eyepiece of some binoculars or a microscope, and it sort of works, but it is far from perfect. [Benedict Diederich] and a team are proving that we can get darn beautiful images with a microscope, a phone holder, and some purpose-built software on an Android phone with their cellSTORM.
The trick to getting useful images is to compare a series of pictures and figure out which pixels matter and which ones are noisy. Imagine someone shows you grainy nighttime footage from an outdoor security camera. When you pause, it looks like hot garbage, and you can’t tell the difference between a patio chair and a shrubbery. As it plays, the noisy pixels bounce around, and you figure out you’re looking at a spruce bush, and that is roughly how the software parses out a crisp image. At the cost of frame rate, you get clarity, which is why you need a phone holder. Some of their tests took minutes, so astrophotography might not fare as well.
With its constant siren song of distraction and endless opportunity for dopamine hits, a smartphone can cause more problems than it solves. The simple solution would be a no-nonsense flip phone, but that offers zero points for style. So why not build your own rotary dial pocket cellphone?
Of course, what style points accrue to [Justine Haupt] take a hit in terms of practicality, but that was never really the point of this build. And even then, the phone appears to be surprisingly useful. It’s based on the rotary dial from a Trimline phone, which itself was an epic hack back in 1965 when it was introduced. The 3D-printed case contains an ATmega2560V microcontroller and an Adafruit FONA 3G cell module, while a flexible mono eInk display adorns the outside. Some buttons, a folding SMA antenna, and some LEDs for signal strength and battery level complete the build, which easily slips into a pocket. The dial can be used not only to dial the phone but to control the speaker volume; in practice, [Justine] mainly uses the speed dial buttons to make calls, though.
We’ve seen rotary phones converted to cell before, but this one is a next-level integration of the retro and the modern. It’s simple, intuitive, and distraction-free, and best of all, it’s a great excuse not to return a text.
The more glass we punch with our fingertips, the more we miss fun physical interfaces like the rotary phone. Sure, they took forever to dial, and you did not want to be one of those kids stuck with one during the transition to DTMF, especially if you were trying to be the 9th caller to a radio station, but the solidly electromechanical experience of it all was just cool, okay? The sound and the heft made them seem so adult.
[Tal O] gets it. He’s all but finished bringing this old girl into the 21st century without giving anything away on her surface. Inside are some things you’d expect, like a SIM800 GSM module for the telephony part, and an ESP32 to count the pulses from the dialer and communicate between it and the GSM module. But it also has a few things we haven’t seen before. The entire journey is outlined in a five-part video series, and we’ve got part one dialed in for you after the break.
Although [Tal] got the ringer working to prove it could be done, he didn’t want to have a separate 12V circuit just to run the bells. Also, the bells and their electromagnets take up a lot of space, so he compromised with an mp3 of a rotary ringer. [Tal] also wanted a way to have dialed-number feedback without cutting up the phone to add a screen, so he found a text-to-speech library and made the phone speak each number aloud as soon as it’s dialed. It uses the same internal speaker as the ringer, but we think it would be neat if the feedback came through the handset speaker.
If [Tal] is looking for another modern convenience to add to this phone, how about speed dial?
When we make a telephone call in 2020 it is most likely to be made using a smartphone over a cellular or IP-based connection rather than a traditional instrument on a pair of copper wires to an exchange. As we move inexorably towards a wireless world in which the telephone line serves only as a vehicle for broadband Internet, it’s easy to forget the last hundred years or more of telephone technology that led up to the present.
The iconic British telephone of the 1960s and 1970s, the GPO model 746. Mine is from 1971. (That isn’t my phone number)
In a manner of speaking though, your telephone wall socket hasn’t forgotten. If you like old phones, you can still have one, and picture yourself in a 1950s movie as you twirl the handset cord round your finger while you speak. Continue reading “A Vintage Phone In 2020”→
Sorry to bear sad tidings, but your car’s extended warranty is about to expire. At least that’s what you’ll likely hear if you answer one of those robocalls that have descended like a plague upon us. We applaud any effort to control the flood of robocalls, even if it means supplementing a commercial blocking service with a DIY ring-blocker.
The commercial service that [Jim] engaged to do his landline blocking is called Nomorobo – get it? It uses the Simultaneous Ringing feature many VoIP carriers support to intercept blacklisted robocallers, but with a catch: it needs caller ID data, so it lets the first ring go through. [Jim]’s box intercepts the ringing signal coming from his Xfinity modem using a full-wave rectifier and an analog input on an Arduino. Once the ring pattern is received, the Arduino flips a relay that connects all the phones in the house to the line, letting the call ring through. If Nomorobo has blocked the call, he’ll never hear a thing. There were a few glitches to deal with, like false positives from going off- and on-hook, but those were handled in software. There’s also a delay in displaying caller ID information on his phones, but it’s a small price to pay for peace.
Any escalation in the war on robocalls is justified, and we applaud [Jim] for his service. Should you feel like joining the fray, step one is to know your enemy. This primer on robocalling will help.
If you’re the kind of person who hates this new generation of smartphone users and longs for a nostalgic past, you’re not far from the new target demographic for many commercial phone manufacturers. Major phone companies like Motorola and Huawei have been developing foldable versions of conventional smartphone designs, intended to be more versatile while maintaining the same functionality as their less flexible counterparts.
It’s certainly gimmicky, but phones like the Samsung Galaxy Fold, the Motorola Razr, and the Huawei MateX are elegant from an engineering perspective. Developing a seamless interface experience, maximizing surface area for functionality, and maintaining the same nostalgic flip phone aesthetic while making use of familiar smartphone features isn’t an easy design process.
For the Razr, a hinge system that takes up about a third of the phone’s internal space allows the OLED display to have no noticeable binder line. Rather than curving like a piece of paper, it forms a teardrop shape that prevents the screen from creasing and being damaged. Springs and pistons below the surface move small places underneath where the user will be tapping – folded in, the plates slide away. It’s an interesting effect, although as you can see in the banner image, it doesn’t quite achieve optically flat perfection.
In order to ensure that the screen doesn’t overheat as it bends, it is made up of microlayers sandwiched together. To balance weight, the circuits and battery is split into two, operating on each half of the device, an unusual design choice for smartphones. Placement of the array of radios and antennas is also a challenge since they can’t be too close to each other or the processor, which can interfere with signal transmission.
Other devices like the Royale Flexpai are more so proof-of-concepts making use of flexible screens and batteries, rather than capturing the aesthetics of a flip phone generation — but who doesn’t want their smartphone to unfold into a tablet when needed? The future of smartphone technology is looking interesting, and we’ll be sure to see even more iterations of flexible displays in the near future.
