Years Don’t Dim The Shine Of These Curious Gadgets

January 13, 2019 by Donald Papp 4 Comments

[Maarten Tromp] recently took the time to document some of the unusual and creative electronic projects he received as gifts over the years. These gadgets were created in the early 2000’s and still work flawlessly today. Two of our favorites are shown here: Hardware Tetris Unit (shown in the image above) and Heap of Electronic Parts.

The “Heap of Electronic Parts” makes sounds when in sunlight.

Heap of Electronic Parts was a kind of hardware puzzle and certainly lives up to its name. It’s a bunch of parts soldered in a mystifying way to the backs of four old EPROMs — the chips with the little window through which UV is used to erase the contents. Assured that the unit really did have a function, [Maarten] eventually figured out that when placed in sunlight, the device ticks, buzzes, and squeals. [Jeroen] had figured out that the EPROMs could act like tiny solar cells when placed in sunlight, and together the four generate just enough power to drive an oscillator connected to a piezo speaker. It still chirps happily away, even today.

Hardware Tetris plays in a terminal window.

Hardware Tetris Unit was a black box intended to be plugged into a serial port. With a terminal opened using the correct serial port settings, a fully-functional Tetris game using ASCII-art graphics could be played. It was even self-powered from the serial port pins.

Inside Hardware Tetris is an AVR microcontroller with some level shifters, and the source code and schematics are available for download. 14 years later, computers no longer have hardware serial ports but [Maarten] says a USB-to-serial converter worked just fine and the device still functions perfectly.

There are a couple more devices documented on [Maarten]’s gifts page, including a Zork-inspired mini text adventure and a hardware board that does some trippy demos on an old Nokia color LCD. [Maarten]’s friend [Jeroen Domburg] (aka Sprite_tm) had a hand in creating most of the gadgets, and he’s someone whose brilliant work we have had the good fortune to feature many times in the past.

Preventing Embedded Fails With Watchdogs

January 12, 2019 by Eric Evenchick 24 Comments

Watchdog timers are an often overlooked feature of microcontrollers. They function as failsafes to reset the device in case of a software failure. If your code somehow ends up in an infinite loop, the watchdog will trigger. This is a necessity for safety critical devices. If the firmware in a pacemaker or a aircraft’s avionics system gets stuck, it isn’t going to end well.

In this oldie-but-goodie, [Jack Ganssle] provides us with a great write up on watchdog timers. This tells the story of a failed Clementine spacecraft mission that could have been saved by a watchdog, and elaborates on the design and implementation of watchdog techniques.

If you’re designing a device that needs to be able to handle unexpected failures, this article is definitely worth a read. [Jack] explains a lot of traps of using these devices, including why internal watchdogs can’t always be trusted and what features make for a great watchdog.

Thanks to [Jan] for the tip!

ESP8266 AC Controller Shows Whats Possible

January 11, 2019 by Tom Nardi 13 Comments

People often get the impression that home built hardware is destined to have a certain amateurish look or feel to it. It’s as though just because you didn’t buy it in a store, it will look cheap or thrown together. While it’s true a hacked together device could look like it was built from the parts bin (and to be fair, sometimes it is), there are plenty of examples of DIY hardware that could give commercial offerings a run for their money.

A case in point is this fantastic ESP8266 air conditioner controller created by [Sitinut Waisara] (Google Translate). Between the simple yet elegant 3D printed enclosure to the very slick user interface on its OLED screen, this project could easily pass as a commercial device. In fact, we’ve seen commercial offerings that didn’t look half this good, let alone offer the same features for what this cost in components and printer filament. It’s a perfect example of what the modern hacker or maker is capable of with the wide array of tools and components currently available to us.

What’s perhaps the most impressive about this project, especially given how good it looks on the outside, is how little there really is on the inside. Beyond the NodeMCU board and SSD1332 OLED display, the only components inside the device are the three tactile buttons, a photoresistor so it can dim the display’s brightness based on ambient light level, an IR LED so it can send commands to the AC unit, and a handful of passives. The hardware side of this design is so simple that [Sitinut] was able to put the whole thing together on a scrap of perfboard. Not that you’d be able to tell when it gets installed into the 3D printed wall-mount enclosure, complete with printed button caps.

While the hardware side of the project might be rather light, the software is anything but. [Sitinut] really went all-in writing his code for the ESP, adding in the little features like the automatic screen dimming and pulling the current time from NTP that often get overlooked in our rush to get a project out the door. He even included a whole collection of icons to display on the OLED screen, which goes a long way towards selling that professional look. But his effort wasn’t limited to cosmetics or clever features, there was also plenty of work put into decoding the IR signals used to control the AC unit and getting all the features and functions plugged into MQTT.

We’ve seen a number of projects that aimed at dragging an existing HVAC system kicking and screaming onto the “Internet of Things”, some considerably less complex than others. But few have had the level of polish that [Sitinut] has put into his controller, so we take our hats off to him.

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Code On Your Phone With CircuitPython Editor

January 10, 2019 by Kristina Panos 17 Comments

[foamyguy] loves Python and messing around with electronics. Boards such as Adafruit’s Circuit Playground Express make it easy for him to take both anywhere. He recently found himself wanting to program Circuit Python boards in the field, but doesn’t always have a laptop on him. So he created an Android app to make on-the-go programming fast and easy.

Using CircuitPython Editor and one or two USB cables, you can program Circuit Python boards with most Android device, including Tinkerboards. It features serial communication, a basic code editor, and a REPL sandbox for code-based castle building. [foamyguy]’s most recent addition to this work in progress is a macro creation tool that lets you edit and store modular, repeatable tasks, like turning all the NeoPixels blue, or lighting them up in a smiley face pattern. The Circuit Python board will draw its power from the Android device, so keep that in mind before you program some crazy light show.

You can get the app in the Play store or download it directly from the ‘hub. If you have any trouble setting it up, check out [foamyguy]’s Adafruit guide.

An Electronic Love Letter To The Wind

January 8, 2019 by Tom Nardi 9 Comments

Home weather stations are a great way for hackers and makers to put their skills to practical use. After all, who wants to hear the current conditions for the whole city when they could setup their own station which drills that information down to their very own street? Such a setup doesn’t need to be any more complex than a temperature sensor wired up to a microcontroller, but then not all of us are quite the weather fanatic that [Richard] clearly is.

The system he’s built to monitor the wind over his home is, to put it mildly, incredible. We might not all share the obsession [Richard] apparently has with the wind, but we can certainly respect the thought and design that went into this comprehensive system. From his scratch built anemometer to the various ways he’s come up with to display the collected environmental data throughout his home, if this build doesn’t inspire you to hack together your own weather station then nothing will.

At the heart of the system is the anemometer itself, which makes use of several scavenged parts such as the bottom halves of plastic Easter eggs as wind cups. The cups spin on a short length of M5 threaded rod inside of a 635ZZ bearing, which ultimately rotates a “light chopper” placed between a red LED and a OPL550A optical sensor. In a particularly nice touch, [Richard] has even included a few power resistors arranged around the moving parts to use as a heater which keeps the device from freezing up when the temperature drops. The sensor creates eight digital pulses per revolution, and feeds data into the base station though a 30 meter (98 feet) cable.

From there, the base station uses an ESP8266 to upload wind and temperature data to ThingSpeak and Weather Underground to be viewed through their respective web interfaces and applications. The project really could have ended here and still been impressive in its own right, but the station also includes 433 MHz and NRF24L01 transmitters to send the data to the other display devices which [Richard] has designed.

The 433 MHZ display is built into the frame of a lantern, and shows the current time and temperature on an LED readout as well as historical wind and temperature graphs on a 2.2 inch ILI9341 TFT screen which [Richard] has rotated into a portrait layout. There’s a red light on top that blinks whenever a signal is received to show that the system is working, and even a touch sensor which can be used to turn off the TFT screen at a tap if you’re not interested in seeing the full charts.

The other display, which [Richard] calls the “picture frame” utilizes a dizzying array of single LEDs, a handful of digital LED readouts, and even an OLED screen for good measure. They all work together to show the current wind speed as well the averages for the past day in three hour segments. As this display features a real time display of current wind conditions and averages for as short a period of two minutes, it uses the NRF24L01 receiver to get data from the base station at a rate of 3 Hz.

In the past we’ve seen 3D printed weather stations, and of course some pretty simple affairs using little more than an ESP8266 board and some sensors. But few have ever put so much thought into how to present the collected data to the user. If you’re serious about knowing what it’s like outside the confines of your bunker, [Richard] has got some tricks to show you.

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Building An ESP8266 Doorbell On Hard Mode

January 7, 2019 by Tom Nardi 29 Comments

It certainly seems as though it should be an easy enough project; all [Miguel De Andrade] wanted was to receive a notification when somebody was pressing his doorbell, and thought it would be a good project to get his feet wet in the wonderful world of ESP8266 hacking. But as fate would have it, not everything went according to plan. In the end he got it sorted out, but it’s an interesting look at how even the “easy” projects can call the gremlins out of hiding.

Arguably, the problems started when [Miguel] picked up an ESP-01 module from a local electronics retailer. While the convenience of buying the hardware in a brick and mortar store can’t be overstated, it did mean he was stuck with a slightly more spartan experience compared to the more common ESP “development boards”. Programming it externally with a Teensy ended up not being much of an obstacle, but it did mean he was stuck with only two GPIO pins.

At any rate, with ESP in hand, the next step was figuring out how the existing bell and intercom system even worked. Unfortunately, after some experimentation [Miguel] found there was a bit more going on there than he’d hoped. According to his multimeter, the one line from the intercom sits at approximately 5 VDC when it’s open, and drops down to 2.5 VDC when pressed. If that wasn’t bad enough, picking up the handset to answer the intercom sent the voltage up to a microcontroller-killing 12 VDC. To complicate maters further, the supply line for the intercom was 23 VAC, so he’d need to rectify that somehow if he wanted to avoid a separate power supply for the ESP.

To turn this jumble of voltages into a nice clean 0 – 3.3 V signal for the ESP8266, he came up with a circuit based around the LM358 comparator that utilizes an LM117 regulator to power itself and the ESP at the same time. A couple of diodes are there to block the AC component from causing trouble, and an A2N2222A transistor is used as a buffer amplifier to boost the output of the comparator so it registers as a digital HIGH on the ESP. The circuit took a bit of fiddling to get sorted out, but in the end [Miguel] says it seems to get the job done.

You might think the problems were solved, but this is where it gets really annoying. The system would work fine for awhile, and then inexplicably go silent. In diagnosing the problem he realized that his circuit connected to GPIO_0 was inadvertently putting the ESP8266 into programming mode, since it was holding the pin LOW unless the intercom button was pressed. He assumed he could just move the circuit to the other GPIO pin, but as that one has the board’s LED on it, that caused its own problems. For now, [Miguel] hasn’t come up with a solution to this issue, and has learned to live with the fact that the system won’t come back up cleanly should it lose power for any reason.

If you’re looking for a slightly classier look than a scrap of perfboard stuck on the wall with what appears to be chewing gum, we’ve also seen the ESP8266 used in some more ornate doorbell setups. Of course if you still haven’t gotten your head wrapped around the whole Internet-connected button thing, you can always start with something a little easier.

Underclocking The ESP8266 Leads To WiFi Weirdness

January 4, 2019 by Tom Nardi 39 Comments

Sometimes the best hacks come from the most basic of questions. In this case, [CNLohr] was wondering what would happen if he started to reduce the clock speed of the ESP8266’s Baseband PLL (BBPLL) while still trying to communicate with it. You know, as one does. The results ended up being fairly surprising, and while it’s not immediately clear if there’s a practical application for this particular trick, it’s certainly worth some additional research.

The idea here is that the BBPLL is the reference clock for the entire system, including all of the peripherals. So underclocking it doesn’t just slow down code execution as you might expect, but it also slows down the chip’s interactions with the outside world. [CNLohr] demonstrates this concept in the video below, showing how the baud rate used to view the serial output from the ESP8266 needs to be adjusted to match the chip’s frequency or else you’ll only get garbage on the line.

But what happens to the WiFi? As [CNLohr] discovered, while the center frequency itself doesn’t change, the channel width gets narrower as the clock rate is lowered. When viewed on the waterfall display of a software defined radio (SDR), the transmission can be seen “compressing” in a step pattern as the clock rate is reduced. As one might expect, the 802.11 packets become indecipherable to a normal WiFi device running in monitor mode. The signal is still at the correct frequency, but the devices can no longer understand each other.

Now it was time for another of those basic questions. What would happen if you did the same thing to a second ESP8266? Much to his surprise, [CNLohr] discovered that the two devices could still communicate successfully as long as their BBPLL clock speed was the same. From an outsider’s perspective it looked like gibberish, but to the two ESPs which had been slowed by the same amount, everything worked as expected even though the 802.11 standards say it shouldn’t.

So what can you do with this? The most obvious application is a “stealth” WiFi connection between ESP8266s which wouldn’t show up to normal devices, a communications channel invisible to all but the most astute eavesdropper. [CNLohr] has made all the source code to pull this trick off public on GitHub, and it should be interesting to see what kind of applications (if any) hackers find for this standards-breaking behavior.

If your thing is devices being forced into operations they were never intended to by particularly twisted hackers, check out our recent coverage of the USB serial adapter turned SDR by [Ted Yapo].

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