Saturday, July 30
16-Bit Audio Output Via Voltage Reference
[Bruce Land] switched his microprocessor programming class over from Atmel parts to Microchip’s PIC32 series, and that means that he’s got a slightly different set of peripherals to play with. One thing that both chips lack, however is a digital-to-analog converter (DAC). Or do they? (Dun-dun-dun-duuuuhnnnn!)
The PIC part has a programmable, sixteen-level voltage reference. And what is a Vref if not a calibrated DAC? With that in mind, [Bruce] took to documenting its performance and starting to push it far beyond the manufacturer’s intentions. Turns out that the Vref has around 200 kHz of bandwidth. (Who would update a voltage reference 200,000 times per second?)
Anyway, [Bruce] being [Bruce], he noticed that the bits weren’t changing very often in anything more than the least significant bit: audio waveforms, sampled fast enough, are fairly continuous. This suggests using a differential PCM encoding, which knocks the bitrate down by 50% and saves a lot on storage. (Links to all the code for this experiment is inline with his writeup.)
The audio hacks that come out of [Bruce]’s Cornell ECE classes are always a treat. From the lock that you have to sing to open, to chiptunes programmed into an FPGA, there’s something for music fans of all inclinations.
Filed under: Microcontrollers, musical hacks
BowFlex smart dumbbells tested: get ripped without leaving the house
Video shot/edited by Jennifer Hahn. (video link)
If you've ever zoned out at the gym in the middle of a set and lost count, here's a solution that will let you zone out as much as you want. BowFlex's new SelectTech 560 smart dumbbells is proof that fitness tech is moving beyond wristbands. This set of two weights is considered "smart" because they allow you to adjust how much you life from one to 60 pounds on each dumbbell, and, as you lift, the dumbbells automatically record every rep. When paired with a mobile app, the smart dumbbells let you "just lift" (literally, that's an in-app exercise) or follow lifting and exercise routines that incorporate the dumbbells.
While the SelectTech 560 sounds like a no-brainer for hardcore lifters who want to exercise at home without investing in an entire rack of weights, there are a few catches: that's 120 pounds of weight you'll have to get into your home, and the set costs $499. Check out the video above to see what I thought of the BowFlex smart dumbbells after I gave them a try.
Read on Ars Technica | Comments
Droolworthy Animatronic Stargate Horus Helmet
It’s incredibly likely that, unless you own one of the original movie props, your Stargate Horus helmet is not as cool as [jeromekelty]’s. We say this with some confidence because [jerome] got access to the original molds and put in an incredible amount of time on the animatronics. (See his latest video embedded below.)
Surprisingly, a number of the parts for this amazing piece were bought off the shelf. The irises that open and close they eyes, for instance, were bought on eBay. This is not to downplay the amount of custom design, though. The mechanism that moves the feathers is a sight to see, and there’s a lot of hand-machined metal holding it all together. But the payoff is watching the thing move under remote control. The eye dimming and closing, combined with the head movements, make it look almost alive.
This isn’t [jerome]’s first Stargate-Horus-Helmet rodeo. He made an Arduino-powered one back in 2011. We can’t wait to see what’s next.
Filed under: misc hacks, wearable hacks
A Crash Sensor For Delta 3D Printers
It doesn’t happen that often, but this is the last time that [Lucas] comes back from hours of unattended 3D printing to find a large portion of plastic spaghetti mess and a partly disassembled Kossel. The crash sensor he designed will now safely halt the printer if it detects that something went wrong during the print.
Unattended 3D printing is even more thrilling if your delta printer’s effector platform attaches to the delta arms through magnetic joints. While magnetic joints have their benefits, a small irregularity in the printing process can cause them to detach. The unknowing printer will then continue to drag a half-attached effector around, until the whole thing, including the still running heater block, comes to rest somewhere. [Lucas’] crash sensor tackles this issue by adding three limit switches. Each switch sits in a 3D printed mount that attaches to one of the delta arm pairs, effectively detecting if the rods are still in place.
[Lucas] wired the switches in series with his filament sensor, so if any of the arm joints fail, the printer will assume that it ran out of filament, stop the print and cool down. If you want to give this clever design a go without the filament sensor, both the Marlin and the Repetier firmware provide a dedicated defect sensor routine for this purpose. Enjoy the video below, where [Lucas] explains his build:
Filed under: 3d Printer hacks
