Ping-Pong Ball Makes Great PID Example

July 31, 2019 by Al Williams 12 Comments

It is a common situation in electronics to have a control loop, that is some sort of feedback that drives the input to a system such as a motor or a heater based upon a sensor to measure something like position or temperature. You’ll have a set point — whatever you want the sensor to read — and your job is to adjust the driving thing to make the sensor read the set point value. This seems easy, right? It does seem that way, but in realitythere’s a lot of nuance to doing it well and that usually involves at least some part of a PID (proportional, integral, derivative) controller. You can bog down in math trying to understand the PID but [Electronoobs] recent video shows a very simple test setup that clearly demonstrates what’s going on with an Arduino, a motor, a distance sensor, and a ping-pong ball. You can see the video below.

Imagine for a moment heating a tank of water as an example. The simple approach would be to turn on the heater and when the water reaches the setpoint, turn the heater off. The problem there is though that you will probably overshoot the target. The proportional part of a PID controller will only turn the heater fully on when the water is way under the target temperature. As the water gets closer to the right temperature, the controller will turn down the input — in this case using PWM. The closer the sensor reads to the setpoint, the lower the system will turn the heater.

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Reflecting On Margaret Hamilton: 50 Years After Apollo 11

July 31, 2019 by Sharon Lin 36 Comments

In celebration of the 50th anniversary of the first Apollo moon landing, Google created a 1.4-square-mile portrait of NASA software developer Margaret Hamilton using more than 107,000 mirrors from the Ivanpah Solar Facility in the Mojave Desert, a solar thermal power plant with a gross capacity of 392 megawatts.

The fields of heliostat mirrors (173,500 in total) ordinarily focus sunlight on receivers located on the solar power towers, which subsequently generate steam to drive steam turbines. The facility was first connected to the electrical grid in September 2013 before formally opening in February 2014, during which it was the world’s largest solar thermal power station. Ivanpah was developed by BrightSource Energy and Bechtel, with Google contributing $168 million towards its $2.2 billion in costs. Google no longer invests in the facility, however, due to the decline of the price of photovoltaic systems.

The facility has historically taken steps to avoid disrupting the natural wildlife, which includes desert tortoises. The effect of mirror glare on airplane pilots, water concerns, and collisions with birds has also been addressed by the operators of the installation.

According to Google, the image was larger than Central Park and could be seen a mile above sea level. The mirrors are all attached to a rotating mount that maneuvers the mirrors in order to create lighter and darker shades to make up the image.

The Apollo 11 mission, manned by Buzz Aldrin, Neil Armstrong, and Michael Collins, was the first to bring humans to the moon in 1969. Hamilton‘s role in the team included programming the in-flight software for all of NASA’s Apollo missions. She had also worked on satellite tracking software for the Air Force through Lincoln Lab (started by the Massachusetts Institute of Technology) and later joined the Charles Stark Draper Laboratory. It was, however, her work on creating computer systems to predict and track weather systems for use in anti-aircraft air defenses that made her a candidate for a lead developer role at NASA.

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Big Ol’ LED Wall Looks Cool, Can Draw Over 170 Amps

July 31, 2019 by Lewin Day 15 Comments

Building giant LED walls comes with a serious set of challenges. Whether they lie in power, cable routing, or just finding a way to clock out data fast enough for all the pixels, it takes some doing to build a decent sized display. [Phill] wanted a statement piece for the office, so rolled up his sleeves and got to work.

The build uses P5 panels, which we’ve seen used before on a smaller scale. Initial testing was done with a Raspberry Pi 3, which started to run out of grunt when the build reached 28 panels. The refresh rate was slow, and anything with motion looked messy. At that point, a dedicated driver was sourced in order to handle the full 48-panel display. Other challenges involved dealing with the huge power requirements – over 170 amps at 5 volts – and building a frame to hold all the panels securely.

The final product is impressive, standing 2 meters wide and 1.2 meters high. Resolution is 384 x 256. With a Mac Mini running video into the display through the off-the-shelf driver, all manner of content is possible. [Phill] even whipped up a Slack channel for users to send GIFs and text messages to the display. Naturally, we’re sure nobody will take advantage of this functionality.

If you’ve got your own giant LED wall, and you’re dying to tell us about it, make sure you get in touch. Video after the break.

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Open Source Smart Display Takes The Long Way Around

July 31, 2019 by Tom Nardi 18 Comments

Thanks to the relatively low cost of the Raspberry Pi and high resolution LCD screens, “smart displays” have become a favorite project of those looking to clear out their parts bins. Just hook the Pi up to the screen, setup some software, and you’ve got yourself a digital bulletin board for your home that can show your schedule, the weather, etc. Build it into a mirror, and you’ve got yourself at least double Internet points.

But when [John Basista] started planning his own smart display, he decided to take the path less traveled. He’s entered the resulting open source project into the 2019 Hackaday Prize, and we’re very excited to see where it goes from here. Even in these early days he’s already made some great strides, with nary a Raspberry Pi in sight.

[John] has nothing against using the Raspberry Pi for these smart displays, and indeed, it has a number of traits which make it particularly well suited to the task. But the problem for him was that it only supported HDMI, and he had his heart set on using an Embedded DisplayPort (eDP) screen. Namely the Innolux N173HCE-E31, a 17.3 inch IPS LCD designed for laptops.

He tried to find a Linux or Android compatible SBC that featured eDP, but found it to be a challenge. There were some x86 options, but didn’t want to go down that road. Eventually he settled on the Dragonboard 410c, which features a quad-core Qualcomm APQ8016E CPU running at 1.2 GHz and 1GB of RAM. This board didn’t have eDP either, but it did have Display Serial Interface (DSI), which he could convert to eDP with the Texas Instruments SN65DSI86 IC.

From there, he started developing a PCB which would hold the Dragonboard 410c and the SN65DSI86. The board also breaks out I2C and UART so he can connect it to various other sensors and gadgetry down the road, and includes all the necessary power regulation to drive everything. The whole thing fits in the palm of your hand, and judging by the renders [John] has put together, should nestle nicely into the back of the 3D printed enclosure when everything is finished.

There’s still quite a bit left to do on this project, but [John] has plenty of time to tie up the loose ends. Currently there’s little information about the software side of things, but as you can see in the video after the break, it’s now running Android which should make things relatively easy.

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Machinist Tools: Edge Finding

July 31, 2019 by Quinn Dunki 35 Comments

Machinists like to live on the edge, but they always want to know precisely where it is. If you’ve watched any machining videos (*cough*) then you’ve seen heavy use of digital readouts on machines. A “DRO” (as the cool kids call them) is a little computer that knows where the slides are, and thus where your cutter is on the piece. However, there’s a catch. DROs don’t know the absolute position of the spindle, they know the relative position of it. The bottom line is that a DRO is just a fancier version of the graduated scales on the hand wheels. The key difference is that the DRO doesn’t suffer from backlash, because it is measuring the slides directly (via glass scales similar to your digital caliper) rather than inferring position from rotations of the leadscrews. With traditional hand wheels, you have to compensate for backlash every time you change direction, and a DRO saves you from that (among other convenience features).

The point is that, whether old school or new, you still only get a relative coordinate system on your part. You need to establish an origin somehow. A useful way to do this is to set an origin at one corner of the part, based on its physical edges. How do you tell the DRO (or hand wheels) where the edges are? Enter the edge finder.

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BootBasic Fits Your Favorite Language In The Boot Sector

July 31, 2019 by Al Williams 18 Comments

Humans seem to have a need to do things that aren’t practical. Make the biggest ball of twine. Engrave the Declaration of Independence on a grain of rice. We want to make things bigger, smaller, faster, or whatever. That might explain why [nanochess] put out bootBASIC.

The 8088 (or later) assembly code gives you a very restricted BASIC interpreter that you can boot up. That means it has to fit in the 512-byte boot block that the hardware loads to get an operating system running. How restricted? Keep in mind it fits in 512 bytes. Each line can only have 19 characters or less. Backspace works, but doesn’t update the screen. Line numbers range from 1 to 999 and there are only 26 integer variables named a through z that hold 16 bits. All statements are in lower case.

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RTL-SDR: Seven Years Later

July 31, 2019 by Tom Nardi 40 Comments

Before swearing my fealty to the Jolly Wrencher, I wrote for several other sites, creating more or less the same sort of content I do now. In fact, the topical overlap was enough that occasionally those articles would get picked up here on Hackaday. One of those articles, which graced the pages of this site a little more than seven years ago, was Getting Started with RTL-SDR. The original linked article has long since disappeared, and the site it was hosted on is now apparently dedicated to Nintendo games, but you can probably get the gist of what it was about from the title alone.

When I wrote that article in 2012, the RTL-SDR project and its community were still in their infancy. It took some real digging to find out which TV tuners based on the Realtek RTL2832U were supported, what adapters you needed to connect more capable antennas, and how to compile all the software necessary to get them listening outside of their advertised frequency range. It wasn’t exactly the most user-friendly experience, and when it was all said and done, you were left largely to your own devices. If you didn’t know how to create your own receivers in GNU Radio, there wasn’t a whole lot you could do other than eavesdrop on hams or tune into local FM broadcasts.

Nearly a decade later, things have changed dramatically. The RTL-SDR hardware and software has itself improved enormously, but perhaps more importantly, the success of the project has kicked off something of a revolution in the software defined radio (SDR) world. Prior to 2012, SDRs were certainly not unobtainable, but they were considerably more expensive. Back then, the most comparable device on the market would have been the FUNcube dongle, a nearly $200 USD receiver that was actually designed for receiving data from CubeSats. Anything cheaper than that was likely to be a kit, and often operated within a narrower range of frequencies.

Today, we would argue that an RTL-SDR receiver is a must-have tool. For the cost of a cheap set of screwdrivers, you can gain access to a world that not so long ago would have been all but hidden to the amateur hacker. Let’s take a closer look at a few obvious ways that everyone’s favorite low-cost SDR has helped free the RF hacking genie from its bottle in the last few years.

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