Two years ago we wrote about a giant robot battle between the USA and Japan. After two years in the making, MegaBots (team USA) and Suidobashi (team Japan) were finally ready for the first giant robot fight. If you are into battle bots, you probably did not miss the fight that happened around 7:00 pm PST. If you missed it, you can watch the whole thing here.
There were two duels. First it was Iron Glory (MkII) vs. Kuratas, and after that it was Eagle Prime (MkIII) vs. Kuratas.
Be warned, spoilers ahead.
Continue reading “About That Giant Robot Battle Last Night”
Encryption is one of the pillars of modern-day communications. You have devices that use encryption all the time, even if you are not aware of it. There are so many applications and systems using it that it’s hard to begin enumerating them. Ranging from satellite television to your mobile phone, from smart power meters to your car keys, from your wireless router to your browser, and from your Visa to your Bitcoins — the list is endless.
One of the great breakthroughs in the history of encryption was the invention of public key cryptography or asymmetrical cryptography in the 70’s. For centuries traditional cryptography methods were used, where some secret key or scheme had to be agreed and shared between the sender and the receiver of an encrypted message.
Asymmetric cryptography changed that. Today you can send an encrypted message to anyone. This is accomplished by the use of a pair of keys: one public key and one private key. The key properties are such that when something is encrypted with the public key, only the private key can decrypt it and vice-versa. In practice, this is usually implemented based on mathematical problems that admit no efficient solution like certain integer factorization, discrete logarithm and elliptic curve relationships.
But the game changer is that the public key doesn’t have to be kept secret. This allows cryptography to be used for authentication — proving who someone is — as well as for encryption, without requiring you to have previously exchanged secrets. In this article, I’ll get into the details of how to set yourself up so that anyone in the world is able to send you an e-mail that only you can read.
Continue reading “Practical Public Key Cryptography”
Who doesn’t like old tools? Even if they aren’t practical to use for production, plenty of old tools still have a life to offer the hobbyist or home worker. Some tools might seem a bit too far gone – due to age, rust, or practicality, to use. That’s where [Hand Tool Rescue] comes in. [HTR] finds rusty, dirty old tools, and brings them back to life. Sometimes they’re practical tools, other times, they’re a bit out there. In a recent video, he restored a BeMaCo automatic saw set from the 1940’s. Saw sets are tools which bend each tooth of a saw blade slightly. Typically they are pliers-like devices.
The slight bend of each tooth on the blade widens the saw’s kerf and prevents binding. Typically these tools are pliers-like devices. The BeMaCo set is something else — it pulls the blade through tooth by tooth, while a spring-loaded head pecks away, bending each tooth. It’s something Rube Goldberg would have loved.
[HTR’s] filming style borrows a lot from [Jimmy DiResta], who we’ve covered here before. There are no words, and most of the video is sped up. Even with the fast video, [HTR] probably has many hours of footage to pare down to a 20-minute video.
The restoration begins with tearing the saw set apart. Every nut and bolt is removed. All the parts are cleaned, chemically de-rusted, and wire-wheeled. Even the motor is torn down, cleaned, and wired up. Then come the re-assembly. [HTR] gets every piece back in its proper place. We’re wondering how many times he had to refer to the teardown video to get everything right. Finally, the saw set is complete — ready for another 70 years of work.
Brushless motors have a lot of advantages over traditional brushed motors. However, testing them can be a bit of a pain. Because the resistance of the motor’s coils is usually very low, a standard resistance check isn’t likely to be useful. Some people use LC meters, but those aren’t as common as a multimeter or oscilloscope. [Nils Rohwer] put out two videos — one two years ago and one recently — showing how to test a brushless motor with a multimeter or scope. Oh, you do need one other thing: a drill.
You don’t have to drill into the motor, instead you use the drill to spin the motor’s shaft. Since a motor and a generator are about the same thing, you can read the voltages produced by the spinning motor and determine if it is good or not. The first video shows the technique and the second, more recent video shows a scope reading a bad motor. You can see both videos, below.
Continue reading “Testing Brushless Motors With A Scope (or A Meter)”