Google Is Building A 100kW Radio Transmitter At A Spaceport And No One Knows Why

You can find the funniest things in public government documents. There’s always ample evidence your local congress critter is working against the interests of their constituency, nation, and industry controlled by the commission they’re chairperson of. Rarely, though, do you find something surprising, and rarer still does it portend some sort of experiments conducted by Google at a spaceport in New Mexico.

In a publication released last week, Google asked the FCC to treat some information relating to radio experiments as confidential. These experiments involve highly directional and therefore high power transmissions at 2.5 GHz, 5.8GHz, 24GHz, 71-76GHz, and 81-86GHz. These experiments will take place at Spaceport America, a 12,000 foot runway in the middle of New Mexico occasionally used by SpaceX, Virgin Galactic, and now Google.

For the most part, this document only tells the FCC that Google won’t be causing harmful interference in their radio experiments. There few other details, save for what bands and transmitters Google will be using and an experimental radio license call sign (WI9XZE) that doesn’t show up in the FCC database.

Of the few details listed in the documents, one thing does pop out as exceptionally odd: a 70-80 GHz transmitter with an effective radiated power (ERP) 96,411 W. That’s close enough to 100 kilowatts to call it as such. This is the maximum effective radiated power of the highest power FM stations in the US, but radio stations are omnidirectional, whereas Google is using very high gain antennas with a beam width of less than half a degree. The actual power output of this transmitter is a mere half watt.

The best guess for what Google is doing out in the New Mexico desert is Project Skybender, a project to use millimeter waves to bring faster Internet to everyone. There aren’t many details, but there is a lot of speculation ranging from application in low Earth orbit to something with Google Loon.

Getting It Right By Getting It Wrong: RepRap And The Evolution Of 3D Printing

The beginning of the DIY 3D printing movement was a heady time. There was a vision of a post-scarcity world in which everything could and would be made at home, for free. Printers printing other printers would ensure the exponential growth that would put a 3D printer in every home. As it says on the front page: “RepRap is humanity’s first general-purpose self-replicating manufacturing machine.” Well, kinda.

RepRapOneDarwin-darwin
Original Darwin. Photo: Adrian Bowyer, founder of RepRap.

Just to set the record straight, I love the RepRap project. My hackerspace put our funds together to build one of the first few Darwins in the US: Zach “Hoeken” came down and delivered the cut-acrylic pieces in person. I have, sitting on my desk, a Prusa Mendel with 3D parts printed by Joseph Prusa himself, and I spent a fantastic weekend with him and Kliment Yanev (author of Pronterface) putting it together. Most everyone I’ve met in the RepRap community has been awesome, giving, and talented. The overarching goal of RepRap — getting 3D printers in as many peoples’ hands as possible — is worthy.

But one foundational RepRap idea(l) is wrong, and unfortunately it’s in the name: replication. The original plan was that RepRap printers would print other printers and soon everyone on Earth would have one. In reality, an infinitesimal percentage of RepRap owners print other printers, and the cost of a mass-produced, commercial RepRap spinoff is much less than it would cost me to print you one and source the parts. Because of economies of scale, replicating 3D printers one at a time is just wasteful. Five years ago, this was a controversial stance in the community.

On the other hand, the openness of the RepRap community has fostered great advances in the state of the DIY 3D printing art. Printers haven’t reproduced like wildfire, but ideas and designs have. It’s time to look back on the ideal of literal replication and realize that the replication of designs, building methods, and the software that drives the RepRap project is its great success. It’s the Open Hardware, smarty! A corollary of this shift in thought is to use whatever materials are at hand that make experimentation with new designs as easy as possible, including embracing cheap mass-produced machines as a first step. The number of RepRaps may never grow exponentially, but the quality and number of RepRap designs can.

Continue reading “Getting It Right By Getting It Wrong: RepRap And The Evolution Of 3D Printing”

Modifications to a Razor E300 motor controller to remove limits

Converting An Electric Scooter To Lithium Batteries And Disabling The Safeties

There’s a bunch of different electric scooters available nowadays, including those hoverboards that keep catching fire. [TK] had an older Razor E300 that uses lead acid batteries. After getting tired of the low speeds and 12 hour charge times, [TK] decided it was time to swap for lithium batteries.

The new batteries were sourced from a Ryobi drill. Each provides 18 V, giving 36 V in series. The original batteries only ran at 24 V, which caused some issues with the motor controller. It refused to start up with the higher voltage. The solution: disable the safety shutdown relay on the motor controller by bridging it with a wire.

With the voltage issue sorted out, it was time for the current limit to be modified. This motor controller uses a TI TL494 to generate the PWM waveforms that drive a MOSFET to provide variable power to the motor. Cutting the trace to the TL494’s current sense pin removed the current limit all together.

We’re not saying it’s advisable to disable all current and voltage limits on your scooter, but it seems to be working out for [TK]. The $200 scooter now does 28 km/h, up from 22 km/h and charges much faster. With gearing mods, he’s hoping to eke out some more performance.

After the break, the full conversion video.

Continue reading “Converting An Electric Scooter To Lithium Batteries And Disabling The Safeties”

Transforming Spice

Spice is a circuit simulator that you should have in your toolbox. While a simulator can’t tell you everything, it will often give you valuable insight into the way your circuit behaves, before you’ve even built it. In the first installment of this three-part series, I looked at LTSpice and did a quick video walkthrough of a DC circuit. In the second, I examined two other parts of Spice: parameter sweeps and AC circuits. In this final installment, I want to talk a bit more about real-world component performance and also look at modeling transformers.

Recap

lowpasssLast time we looked at a low pass filter, but it wasn’t practical because the components were too perfect. Only in simulation do voltage sources and wires have zero resistance. There was no load resistance either, which is unlikely. Even an oscilloscope probe will load the circuit a little.

The resulting AC analysis showed a nice filter response that was flat to about 1 kHz and then started roll off as the frequency increased. Suppose the source had an 8 ohm series resistor. How does that change the circuit response?

Continue reading “Transforming Spice”

Odroid C2 Bests Raspberry Pi 3 In Several Ways

It’s been a big week in the world of inexpensive single board computers, and everyone’s talking about the new Raspberry Pi 3. It blows away the competition they say, nobody can touch it for the price.

Almost nobody, that is.

With a lot less fanfare on these shores, another cheap and speedy 64-bit quad-core ARM-based SBC slips onto the market this week, Hardkernel’s Odroid C2. And looking at the specification it seems as though the Pi 3 may be given a run for its money. Like the BCM2837 in the Pi 3 its Amlogic S905 SoC is a quad-core ARM Cortex-A53, but the C2’s 2GHz clock speed gives the raspberry to the 1.2GHz of the Pi 3. There is twice the RAM of the Pi 3 at 2Gbytes, and the onboard Mali-450 GPU can deliver 4K video.

Unlike the Pi 3 there is no wireless or Bluetooth on board, but the C2 has a Gigabit Ethernet port which is wired directly into the SoC. Compared to the Pi 3’s 100 megabit port which suffers through being on a USB interface, that’s likely to be very quick.

Storage can be a choice of either the usual micro SD card or eMMC. Given that the two boards share a very similar form factor it is no surprise that they have very similar GPIO capabilities, however it is worth noting that the C2 has a built-in analog-to-digital converter. As to operating systems, the C2 can run Ubuntu 16.04, or Android Lollipop.

Of course, we’ve seen so many boards touted as Pi-killers, and like all those also-ran tablets touted as iPad killers a few years ago we’ve never heard of most of them again after a brief moment of chatter. They look so good on paper but the price always lets them down.

The C2 could just escape that fate though, its $40 price point is very close to that of the Pi 3. Setting aside for a moment how much shipping and customs might cost for a package from Korea, that sounds interesting to us.

Why might you buy a C2 then, and why might you buy a Pi 3? That the C2 has a much faster processor is beyond doubt. This and its faster wired networking would make it a much more interesting prospect for anyone whose work involves network-attached data processing. But even though a USB wireless network adaptor can be had for only a few dollars the Pi 3’s onboard wi-fi and Bluetooth makes it much more attractive to a home user or someone using a computer on a platform unfettered by wires.

However impressive the C2 may be it is overwhelmingly likely that the Pi 3 will outsell it many times over. This will not just be due to the massive publicity advantage achieved by the Pi Foundation, but the huge ecosystem of hardware and software developers that have made the Pi boards perform to the limit of their abilities in all directions. If you don’t mind forgoing that support though, you could just find that the board from Korea gives you enough extra bang for your buck to make having it on your bench worthwhile.

We’ve followed the Odroid products from the start here at Hackaday. The C2 is just the latest of a procession of boards from Hardkernel, and we’ve featured a few projects that include them. Theirs is always the name at the top of the list when the subject turns to Raspberry Pi competitors, perhaps with the C2 they’ve got a winner.

Our thanks to [Derrick].

Hack A PS/2 Keyboard Onto Your Pi Zero

Hacking for the Raspberry Pi Zero is a tricky proposition. Whatever you do, you’re working with a nominal five dollar board, so your hacks can’t be too highfalutin. For instance, a decent PS/2 to USB adapter will cost you as much as the Zero did, if not more. But if you just need to drive your Pi Zero from your old Model M (we hear you!) you’ve got to do it on the cheap.

So when prolific Pi hacker [mincepi] set out to build a PS/2 adapter, some corners were cut. PS/2 is a clocked data protocol, but the good news is that the clock doesn’t start and stop all the time as in I2C or SPI. This means that if you poll the data line at just the right frequency, at least in principle you’ll be able to ignore the clock.

ps2-schematic_border

So that’s what [mincepi] did. As you can see in the schematic and the banner image, there’s nothing to it. Two resistors provide the pullup voltage for the clock and data lines. And here’s a gem: a green LED with a drop voltage of about 2 V converts the 5 V data line down to something that the Pi Zero’s 3.3 V won’t get fried with. Cute, and very much in keeping with the spirit of the hack. You might be tempted to scrounge up a 3.3 V zener diode from somewhere just to be on the safe side, but remember, it’s a five dollar computer you’re protecting.

The last piece is a custom kernel module for the Pi that polls the PS/2 data line at just the right frequency. If you’re not a Linux person and “compiling a kernel module” sounds scary, [mincepi] has even put together a nice guide for the Raspbian distribution that he’s using. It should work with minor tweaks for any other distro.

We said [mincepi] is a prolific Pi hacker and here’s the proof: we’ve covered his quick-and-dirty VGA output hack and a scheme to get analog sound input into the Pi Zero just in the last couple of weeks. Hack on!

Star Trek Pi

Every time we yell out, “OK Google… navigate to Velvet Melvin’s” we feel like a Star Trek character. After all, you’ve never seen Captain Kirk (or Picard) using a keyboard. If you get that same feeling, and you have a Raspberry Pi project in mind, you might enjoy the Raspberry Pi LCARS interface.

You can see the results in the video below. The interface uses PyGame, and you can customize it with different skins if you don’t want a Star Trek look.

Continue reading “Star Trek Pi”