It’s About Time We Saw Another Infinity Mirror Clock

December 14, 2019 by Kristina Panos 5 Comments

Have you made an infinity mirror yet? They’re pretty much a rite of passage project at this point. But unlike that DIY power supply, most of them serve no function beyond looking cool (not that there’s anything wrong with that). Might as well make it do something, right?

[How Do You – DIY] has a built a few mirrors because he likes experimenting with the effects of different reflective surfaces in various positions. This time, he’s built a clock from the ground up. Basic infinity mirror rules apply here, though he used semi-transparent reflective film on both sides for greater effect and put an adjustable warping bar in the back so the trail curves toward the center. The actual timekeeping is done by an Arduino Nano.

The RGB LEDs on his strip were a few millimeters too far apart for his liking, so he added a few dozen hours to the build by cutting it apart and painstakingly placing them all around the wood frame. Then he Dremeled a groove for each set of three wires that link the LEDs so that they sit flush. The final product is beautiful, and it’s a shame that this LED-holding frame is hidden away inside the equally well-crafted aluminium frame.

Don’t waste another minute — sweep past the break to check out the build video. If it’s a portable and functional conversation piece you want, make a set of infinity mirror coasters.

Oh, and did we mention that we’re running a clock contest? Hint, hint.

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An Arduino And An Enigma All Rolled Into One

December 12, 2019 by Gerrit Coetzee 7 Comments

This hacker has been wanting to design an Enigma machine simulator for a while, but didn’t take the leap until they realized there was a compact Arduino with a surplus of I/O.

The logs go through all sort of variations on the machine. Everything from a plug board variation similar to the original to a 16 segment LED tester are covered. In one of the posts you can even see it decode a real U-Boat message.

The earlier revisions are housed in very attractive laser cut cases but the latest designs employ an even more elegant casing solution. The simulator uses 16 segment displays and momentary push buttons for the keys. At its core is a 2560 Pro mini. The write-up contains a lot of detail about the code behind the Enigma and is interesting to read. Interestingly, the PCB was designed in Fritzing, the EDA software many love to hate.

We love the craftsmanship and attention going into this project and can see it turning into a very appealing kit as it goes through its design cycles.

Programmable Wrist Synth Pushes The Envelope

December 11, 2019 by Kristina Panos 7 Comments

Synths are a ton of fun no matter how good or bad they sound. Really, there are no bad-sounding ones, it’s just that some are more annoying to listen than others to if you’re not the one making the beep boops. [Clem] had built a tiny LDR-based synth into a watch case a few years back and took it to many a Maker Faire, where it delighted and annoyed until it ultimately broke.

Naturally, it was time to make a new version that’s more capable. Whereas the first one was Atari-punk-console-meets-light-Theremin, this one has a bunch of inputs and can be programmed on the fly to record and play back bendable tones. It’s driven by an Arduino MKR, and the inputs are managed by an impressively squash bug-wired shift register. [Clem] used beefy switches this time in the hopes that this one will last longer. We think the slide pots are a great touch, as are the candy-colored knobs printed in PMMA.

Our favorite part is that [Clem] took advantage of the random states the microcontroller pins are in when it’s first powered on. If you don’t want to program any notes, you can use the ones generated at boot and just play around with those. Be sure to check out the build video after the break.

We’ve seen our share of synths, but few as delicious-looking as KELPIE from this year’s Hackaday Prize.

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Death To All Coca Cola Cans With This Miniature Arduino Powered Cannon

December 8, 2019 by Gerrit Coetzee 8 Comments

[MJKZZ] sends in this entertaining little tutorial on building a small automated cannon out of a syringe.

He starts the build off by modifying an arc lighter, the fancy kind one might use to light a fire on a windy day, so that it can be controlled by a micro-controller. The arc is moved to the needle end of the syringe with a careful application of wires and hot glue. When the syringe is filled with a bit of alcohol and the original plunger is pressed back in a small spark will send it flying back out in a very satisfying fashion.

Of course it wouldn’t be a proper hack without an Arduino added on for no reason other than the joy of doing so. [MKJZZ] adds an ultrasonic sensor into the mix which, when triggered appropriately by an invading object fires the arc lighter using a reed relay.

He demonstrates the build by eliminating an intruding coke can on his work bench. You can see it in the video after the break. All in all a very fun hack.

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ESP32 Audio Sampling With Interrupts And IRAM

December 7, 2019 by Al Williams 9 Comments

Interrupting while someone is talking is rude for humans, but smart for computers. [Ivan Voras] shows how to use interrupts to service the ESP32 analog to digital converters when sampling sound. Interestingly, he uses the Arduino IDE mixed with native ESP-IDF APIs to get the best performance.

Like most complex interrupt-driven software, [Ivan’s] code uses a two-stage interrupt strategy. When a timer expires, an interrupt occurs. The handler needs to complete quickly so it does nothing but set a flag. Another routine blocks on the flag and then does the actual work required.

Because the interrupt service routine needs to be fast, it has to be in RAM. [Ivan] uses the IRAM_ATTR attribute to make this work and explains what’s going on when you use it.

…the CPU cores can only execute instructions (and access data) from the embedded RAM, not from the flash storage where the program code and data are normally stored. To get around this, a part of the total 520 KiB of RAM is dedicated as IRAM, a 128 KiB cache used to transparently load code from flash storage.The ESP32 uses separate buses for code and data (“Harvard architecture”) so they are very much handled separately, and that extends to memory properties: IRAM is special, and can only be accessed at 32-bit address boundaries.

This is very important because some ESP-IDF calls — including adc1_get_raw — do not use this attribute and will, therefore, crash if they get pushed out to flash memory. At the end, he muses between the benefit of using an OS with the ESP32 or going bare metal.

If you want to know more about the Arduino on ESP32, we covered that. We also dug deeper into the chip a few times.

Upgrade Your Shades To Find Lost Items

December 7, 2019 by Sharon Lin 8 Comments

Ever wish you could augment your sense of sight?

[Nick Bild]’s latest hack helps you find objects (or people) by locating their position and tracking them with a laser. The device, dubbed Artemis, latches onto your eyeglasses and can be configured to locate a specific object.

Images collected from the device are streamed to an NVIDIA Jetson AGX Xavier board, which uses a SSD300 (Single Shot MultiBox Detection) model to locate objects. The model was pre-trained with the COCO dataset to recognize and localize 80 different object types given input from images thresholded in OpenCV. Once the desired object is identified and located, a laser diode activates.

Probably due to the current thresholds, the demo runs mostly work on objects placed further apart against a neutral background. It’s an interesting look at applications combining computer vision with physical devices to augment experiences, rather than simply processing and analyzing data.

The device uses two servos for controlling the laser: one for X-axis control and the other for Y-axis control. The controls are executed from an Adafruit Itsy Bitsy M4 Express microcontroller.

Perhaps with a bit more training, we might not have so much trouble with “Where’s Waldo” puzzles anymore.

Check out some of our other sunglasses hacks, from home automation to using LCDs to lessening the glare from headlights.

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Automated Cat Feeder Leaves Little To Chance

December 5, 2019 by Tom Nardi 11 Comments

We often like to say that if something is worth doing, then it’s worth overdoing. This automatic cat feeder built by [krizzli] is a perfect example of the principle. It packs in far more sensors and functions than its simple and sleek outward appearance might suggest, to the point that we think this build might just set the standard for future projects.

The defining feature of the project is a load cell located under the bowl, which allows the device to accurately measure out how much feed is being dispensed by weight. This allows the feeder to do things such as detect jams or send an alert once it runs out of food, as well as easily adjust how much is dispensed according to the animal’s dietary needs. To prevent any curious paws from getting into the machine while it’s doling out the food, the lid will automatically open and close during the filling process, complete with optical sensors to confirm that it moved as expected.

All of the major components of the feeder were printed out on a Prusa i3 MK3S, and [krizzli] says that the feed hopper can be scaled vertically if necessary. Though at the current size, it’s already packing around a week’s worth of food. Of course, this does depend on the particular feline you’re dealing with.

In terms of electronics, the feeder’s primary control comes from an ESP8266 (specifically, the Wemos D1 Mini), though [krizzli] also has a Arduino Pro Mini onboard so there’s a few more GPIO pins to play with. The food is dispensed with a NEMA 17, and a 28-BYJ48 stepper is in charge of moving the lid. A small OLED on the side of the feeder gives some basic information like the time until the next feeding and the dispensed weight, but there’s also a simple API that lets you talk to the device over the network. Being online also means the feeder can pull the time from NTP, so kitty’s mealtime will always be on the dot.

Over the years we’ve seen an incredible array of automatic cat feeders, some of which featuring the sort of in-depth metrics possible when you’ve got on onboard scale. But we can’t help but be impressed with how normal this build looks. If nothing else, of all the feeders we’ve seen, this one is probably the most likely to get cloned and sold commercially. They say it’s the most sincere form of flattery.