Source: Hacker News
Source: Hacker News
Source: Hack a Day
If you’re like us, you’ve never spent a second thinking about what happens when you dunk an ordinary LED into liquid nitrogen. That’s too bad because as it turns out, the results are pretty interesting and actually give us a little bit of a look at the quantum world.
The LED fun that [Sebastian] over at Baltic Lab demonstrates in the video below starts with a bright yellow LED and a beaker full of liquid nitrogen. Lowering the powered LED into the nitrogen changes the color of the light from yellow to green, an effect that reverses as the LED is withdrawn and starts to warm up again. There’s no apparent damage to the LED either, although we suppose that repeated thermal cycles might be detrimental at some point. The color change is quite rapid, and seems to also result in a general increase in the LED’s intensity, although that could be an optical illusion; our eyes are most sensitive in the greenish wavelengths, after all.
So why does this happen? [Sebastian] goes into some detail about that, and this is where quantum physics comes into it. The color of an LED is a property of the bandgap of the semiconductor material. Bandgap is just the difference in energy between electrons in the valence band (the energy levels electrons end up at when excited) and the conduction band (the energy levels they start at.) There’s no bandgap in conductive materials — the two bands overlap — while insulators have a huge bandgap and semiconductors have a narrow gap. Bandgap is also dependent on temperature; it increases with decreasing temperature, with different amounts for different semiconductors, but not observably so over normal temperature ranges. But liquid nitrogen is cold enough for the shift to be dramatically visible.
We’d love to see the color shift associated with other cryogens, or see what happens with a blue LED. Want to try this but don’t have any liquid nitrogen? Make some yourself!
Source: Hack a Day
If you’re like us, you’ve never spent a second thinking about what happens when you dunk an ordinary LED into liquid nitrogen. That’s too bad because as it turns out, the results are pretty interesting and actually give us a little bit of a look at the quantum world.
The LED fun that [Sebastian] over at Baltic Lab demonstrates in the video below starts with a bright yellow LED and a beaker full of liquid nitrogen. Lowering the powered LED into the nitrogen changes the color of the light from yellow to green, an effect that reverses as the LED is withdrawn and starts to warm up again. There’s no apparent damage to the LED either, although we suppose that repeated thermal cycles might be detrimental at some point. The color change is quite rapid, and seems to also result in a general increase in the LED’s intensity, although that could be an optical illusion; our eyes are most sensitive in the greenish wavelengths, after all.
So why does this happen? [Sebastian] goes into some detail about that, and this is where quantum physics comes into it. The color of an LED is a property of the bandgap of the semiconductor material. Bandgap is just the difference in energy between electrons in the valence band (the energy levels electrons end up at when excited) and the conduction band (the energy levels they start at.) There’s no bandgap in conductive materials — the two bands overlap — while insulators have a huge bandgap and semiconductors have a narrow gap. Bandgap is also dependent on temperature; it increases with decreasing temperature, with different amounts for different semiconductors, but not observably so over normal temperature ranges. But liquid nitrogen is cold enough for the shift to be dramatically visible.
We’d love to see the color shift associated with other cryogens, or see what happens with a blue LED. Want to try this but don’t have any liquid nitrogen? Make some yourself!
Source: Hacker News
Source: Ars Technica
Enlarge / A photo of the myQ app from LiftMaster's website. (credit: Liftmaster)
Chamberlain Group—the owner of most of the garage door opener brands like LiftMaster, Chamberlain, Merlin, and Grifco—would like its customers to stop doing smart home things with its "myQ" smart garage door openers. The company recently issued a statement decrying "unauthorized usage" of its smart garage door openers. That's "unauthorized usage" by the people who bought the garage door opener, by the way. Basically, Chamberlain's customers want to trigger the garage door and see its status through third-party smart home apps, and Chamberlain doesn't want that.
Here's the statement:
Chamberlain Group recently made the decision to prevent unauthorized usage of our myQ ecosystem through third-party apps.
This decision was made so that we can continue to provide the best possible experience for our 10 million+ users, as well as our authorized partners who put their trust in us. We understand that this impacts a small percentage of users, but ultimately this will improve the performance and reliability of myQ, benefiting all of our users.
We encourage those who were impacted to check out our authorized partners here: https://www.myq.com/works-with-myq.
We caught wind of this statement through the Home Assistant blog, a popular open source smart home platform. The myQ integration is being stripped from the project because it doesn't work anymore. Allegedly, Chamberlain has been sabotaging Home Assistant support for a while now, with the integration maintainer, Lash-L, telling the Home Assistant blog, "We are playing a game of cat and mouse with MyQ and right now it looks like the cat is winning."
Source: Hacker News
Source: Hacker News
Source: Hack a Day
A new BeagleBoard is on the way, full of FPGA hotness: the BeagleV-Fire has been announced. The new $150 Single-Board Computer (SBC) from the pioneering open source BeagleBoard company is built around a RISC-V chip that has FPGA features built in. The BeagleV-Fire is built around the snappily named Microchip PolarFire MPFS025T FCVG484E, a System on a Chip (SoC) that has five Reduced Instruction Set Coding Version 5 (RISC-V) cores and a big chunk of FPGA fabric built in. That means it combines the speed of RISC-V processors with the flexibility of Field Programmable Gate Arrays (FPGA), a big pile of logic gates that can be reprogrammed.
The new BeagleV-Fire includes a sizeable chunk of FPGA to work with: the core chip includes 23 K logic elements and 68 Math blocks, plus 4 Serializer/Deserializer (SerDer) lanes that can throw about 12.7 Gbps of data into and out of the fabric. On the BeagleV-Fire, the main chip is supported by 16 GB of eMMC and 2 GB of LPDDR4 RAM, plus a micro SD slot for extra storage. Gigabit Ethernet is also included, plus USB-C power and a few serial connections for debugging. There is no WiFi built in, but there is an M.2 Key E connection were you could plug in an a wireless adapter if you need it.
Like most other BeagleBoards, the BeagleV-Fire has two headers with 92 pins, which offer access to pretty much every signal on the board, plus lots of analog to digital stuff that works with add-on boards (BeagleBoard refers to them as capes). Also present is the usual 22-pin CSI connector for attaching cameras and other devices.
Want one? They are available for immediate order on BeagleBoard.org or from the usual suspects. It looks like they are already in stock for next-day delivery. If this all sounds familiar, it’s probably because we’ve been posting about this particular board for awhile now, covering both the announcement and first tests.
