Making better noises with dual PWM

pwm_16b_sm

Although it’s technically possible to get 16 bits of resolution on a ATMega328, most implementations of PWM on everyone’s favorite ‘mega – including just about every Arduino sketch – are limited to 8 bit PWM. This means the pins can only output 256 different values, so if you’re playing around with music made on an Arduino don’t expect very high fidelity.

There is a clever way around this: use two PWMs, and use one pin for high bytes and another for low bytes. That’s what Open Music Labs did when working on a synthesizer project that needed very high quality audio.

The basic idea behind the build is that PWM pins can be used to create audio frequencies. Using two PWM pins and adding them together means it’s possible to add extra bits of resolution. This requires using different values of resistors on each pin. For example, using the same value of resistors on two PWM pins increases the resolution by one bit. Two pins with a resistor value ratio of 1:4 increases the resolution by four bits, and so on.

There’s a great tutorial for setting up these higher resolution, dual PWM outputs on an ATMega or Arduino, as well as a distortion analysis for this dual PWM setup.

3D printer gets a big resolution improvement

[Jose Carlos Veloso Junior] has been working on his 3D printer to improve the resolution. We looked in on his project back in October when he was printing the blue busts like the one seen above.

We were impressed by the resolution he was able to achieve back then, using liquid resin that is cured with visible light. The resin creates a thin layer on a glass tray, and is cured when a projector shines precisely positioned light from below. The cured resin is then lifted on the Z-axis, and the next layer in the printing process is hardened by the projector’s light.

Well, this newest rendition far outperforms the initial iteration. The bust on the right looks like it’s been hand-buffed to remove the layer lines, but it actually just came off of the printer. [Jose] made a video of the new equipment in action, which you can watch after the break. He’s keeping most of the juicy bits to himself but he did tell us that the improvement he achieved were due to multiple changes in the process. He tweaked the software to use a more precise curing time, the resin formula has been improved, the ability to isolate pixels without hardening resin around them has been stepped up, and he’s made changes to the way the printer is calibrated and how it lifts the hardened model.

This is fantastic. Kudos to you sir!

[Read more...]

Stylin’ HMD

Watch out, these sunglasses are actually a head mounted display. [Staffan] says he’s wanted dataglasses since ’95, but whats currently out there makes the user look ridiculous, and we have to agree. While his forum posts are a little lacking in detail, he’s promised us more info soon. And for now lets us know at least the resolution, well sort of: Its either 480×1280 or 480x427x3, you can be the judge. Update: [Staffan] has clarified “The resolution is 480*1280 true pixels. It is accomplished by spanning the screen across two Kopin CyberDisplay VGA modules.”

Regardless, [Staffan] is looking for help perfecting the glasses, with what in particular we’re not sure, but the project looks promising and we hope he keeps up the good work.

Cramming more pixels into a Thinkpad

Not willing to settle for 1400×1050 on his Thinkpad, [Lawrence Sheed] set out to upgrade the LCD screen. He ordered a 15″ replacement screen that brought the eye candy up to an impressive 2048×1536 QXGA format. The replacement fits perfectly for a nice factory look. Other than some delicate disassembly you might need to flash the EDID but in [Lawrence's] case it wasn’t necessary. If you’re going to haul around a full-blown laptop it might as well have some killer resolution and now you know how to make that happen.

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