Developing first petahertz-speed phototransistor in ambient conditions

https://news.arizona.edu/news/u-researchers-developing-worlds-first-petahertz-speed-phototransistor-ambient-conditions

#HackerNews #Developing #phototransistor #petahertz #ambientconditions #techinnovation #HackerNews

Worlds first petahertz transistor at ambient conditions

https://news.arizona.edu/news/u-researchers-developing-worlds-first-petahertz-speed-phototransistor-ambient-conditions

#HackerNews #WorldsFirstPetahertz #Transistor #AmbientConditions #Phototransistor #TechInnovation #FutureOfElectronics

It's quite a versatile component.

#electronics #component #transistor #phototransistor #datasheet

30 mars 1950 : Murray Hill dans le New Jersey annonce l'invention du #phototransistor. #histoire #cejourla #invention

Glow In The Dark Computer Memory Illuminates The Fundamentals

Computer memory has taken on many forms over the years, from mercury-based delay-line tubes to handwoven magnetic core. These days, volatile storage using semiconductors has become ubiquitous with computing, but what if there was a better way? [Michael Kohn] has been working on a new standard for computer memory that uses glow in the dark stickers.

Clearly we jest, however we're still mighty impressed by the demonstration. Eight delightful star-shaped phosphorescent stickers represent eight bits of memory, totaling one byte. The glow in the dark material is stuck to the inside of short cylinders, each of which contains a white LED and a phototransistor. The memory array is wired up to an iceFUN FPGA board, which is then connected via level shifters to a Western Design Center MENSCH single board computer.

To write a '1' to memory is as simple as writing to the corresponding memory address using 6502/65C816 assembly language. Using the STA command will illuminate the white LED at that memory address, in turn irradiating the glow in the dark sticker and 'saving' the state. Conversely, LDA at the same address will read from the phototransistor, which picks up the glow (or lack thereof) emitted from the sticker.

A refresh cycle is needed to sustain the 0s and 1s across the memory array as the phosphorescence fades, not dissimilar to modern DRAM requiring frequent recharging to maintain memory contents. The entire setup is a tangible demonstration of the fundamentals of volatile computer memory, and would make for a fun beginner project. [Michael] has more details on his website and GitHub page.

While the FPGA board has its own little set of blinkenlights, an 8-bit RGB LED array would make this project even brighter.

#computerhacks #hardware #6502 #memory #phototransistor #ram #volatile

Take a Look at This Optical Keyboard

Making keyboards is easy, right? Just wire up a bunch of switches matrix-style to a microcontroller, slap some QMK and a set of keycaps on there and you're good to go. Well, yeah, that might work for cushier environments like home offices and Hackaday dungeons, but what if you need to give input under water, in a volatile area, or anywhere else you'd have to forego the clacking for something hermetically sealed? Mechanical switches can only take you so far -- at some point, you have to go optical.

This gorgeous keyboard works with reflected IR beams to determine when a finger is occupying a given key site (because what else are you going to call them?). Each key site has an IR LED and a phototransistor and it works via break-beam.

[BenKoning] wanted a solution that would be easy for others to build, with a low-cost BOM and minimal software processing cost. It just so happens to be extremely good-looking, as well.

The reason you can't see the guts is that black layer -- it passes infrared light, but is black to the eye. The frosted layer diffuses the beams until a finger is close enough to register. Check it out in action after the break, and then feed your optical key switch cravings with our own [Bob Baddeley]'s in-depth exploration of them.

#peripheralshacks #extreme #irled #keyboard #opticalkeyboard #phototransistor

One Man’s Quest to Build a Baby Book With Brains

Regular readers will know that Hackaday generally steers clear of active crowdfunding campaigns. But occasionally we do run across a project that's unique enough that we feel compelled to dust off our stamp of approval. Especially if the campaign has already blasted past its funding goal, and we don't have to feel bad about getting you fine folks excited over vaporware.

It's with these caveats in mind that we present to you Computer Engineering for Babies, by [Chase Roberts]. The product of five years of research and development, this board book utilizes an internal microcontroller to help illustrate the functions of boolean logic operations like AND, OR, and XOR in an engaging way. Intended for toddlers but suitable for curious minds of all ages, the book has already surpassed 500% of its funding goal on Kickstarter at the time of this writing with no signs of slowing down.

The electronics as seen from the rear of the book.

Technical details are light on the Kickstarter page to keep things simple, but [Chase] was happy to talk specifics when we reached out to him. He explained that the original plan was to use discreet components, with early prototypes simply routing the button through the gates specified on the given page. This worked, but wasn't quite as robust a solution as he'd like. So eventually the decision was made to move the book over to the low-power ATmega328PB microcontroller and leverage the MiniCore project so the books could be programmed with the Arduino IDE.

Obviously battery life was a major concern with the project, as a book that would go dead after sitting on the shelf for a couple weeks simply wouldn't do. To that end, [Chase] says his code makes extensive use of the Arduino LowPower library. Essentially the firmware wakes up the ATmega every 15 ms to see if a button has been pressed or the page turned, and updates the LED state accordingly. If no changes have been observed after roughly two minutes, the chip will go into a deep sleep and won't wake up again until an interrupt has been fired by the yellow button being pressed. He says there are some edge cases where this setup might misbehave, but in general, the book should be able to run for about a year on a coin cell.

[Chase] tells us the biggest problem was finding a reliable way to determine which page the book was currently turned to. In fact, he expects to keep tinkering with this aspect of the design until the books actually ship. The current solution uses five phototransistors attached to the the MCU's ADC pins, which receive progressively more light as fewer pages are laying on top of them. The first sensor is exposed when the second page of the book is opened, so for example, if three of the sensors are seeing elevated light levels the code would assume the user is on page four.

Opening to the last page exposes all five light sensors.

The books and PCBs are being manufactured separately, since as you might expect, finding a single company that had experience with both proved difficult. [Chase] plans on doing the final assembly and programming of each copy in-house with the help of family members; given how many have already been sold this early in the campaign, we hope he's got a lot of cousins.

So what do you do with an Arduino-compatible book when Junior gets tired of it? That's what we're particularly interested in finding out. [Chase] says he's open to releasing the firmware as an open source project after the dust settles from the Kickstarter campaign, which would give owners a base to build from should they want to roll their own custom firmware. Obviously the peripheral hardware of the book is fairly limited, but nothing is stopping you from hanging some sensors on the I2C bus or hijacking the unused GPIO pins.

If you end up teaching your copy of Computer Engineering for Babies some new tricks, we've love to hear about it.

#arduinohacks #crowdfunding #microcontrollers #toyhacks #atmega328pb #book #coincell #phototransistor

Measuring LED Flicker, With Phototransistor and Audio App

No one likes a flickering light source, but lighting is often dependent on the quality of a building's main AC power. Light intensity has a close relation to the supply voltage, but bulb type plays a role as well. Incandescent and fluorescent bulbs do not instantly cease emitting the instant power is removed, allowing their output to "coast" somewhat to mask power supply inconsistencies, but LED bulbs can be a different story. LED light output has very little inertia to it, and the quality of both the main AC supply and the bulb's AC rectifier and filtering will play a big role in the stability of an LED bulb's output.

The DIY photosensor takes the place of the microphone input.

[Tweepy] wanted to measure and quantify this effect, and found a way to do so with an NPN phototransistor, a resistor, and a 3.5 mm audio plug. The phototransistor and resistor take the place of a microphone plugged into the audio jack of an Android mobile phone, which is running an audio oscilloscope and spectrum analyzer app. The app is meant to work with an audio signal, but it works just as well with [Tweepy]'s DIY photosensor.

Results are simple to interpret; the smoother and fewer the peaks, the better. [Tweepy] did some testing with different lighting solutions and found that the best performer was, perhaps unsurprisingly, a lighting panel intended for photography. The worst performer was an ultra-cheap LED bulb. Not bad for a simple DIY sensor and an existing mobile phone app intended for audio.

Want a closer look at what goes into different LED bulbs and how they tick? We have you covered. Not all LED bulbs are the same, either. Some are stripped to the bone and others are stuffed with unexpected goodness.

#ledhacks #flicker #ledbulb #lightbulb #photosensor #phototransistor