The Flight Of The Seagull: Valentina Tereshkova, Cosmonaut

June 12, 2018 by 47 Comments

That the Cold War was a tense and perilous time in history cannot be denied, and is perhaps a bit of an understatement. The world stood on the edge of Armageddon for most of it, occasionally stepping slightly over the line, and thankfully stepping back before any damage was done.

As nerve-wracking as the Cold War was, it had one redeeming quality: it turned us into a spacefaring species. Propelled by national pride and the need to appear to be the biggest kid on the block, the United States and the Soviet Union consistently ratcheted up their programs, trying to be the first to make the next major milestone. The Soviets made most of the firsts, making Sputnik and Gagarin household names all over the world. But in 1962, they laid down a marker for a first of epic proportions, and one that would sadly stand alone for the next 19 years: they put the first woman, Valentina Tereshkova, into space.

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3D Print A Remote Control Flame Thrower

June 12, 2018 by 11 Comments

We all have a weakness for a good flamethrower project, but sometimes they can look a little hairy, even if losing hairs to them seems to be the order of the day. [Hyper_Ion] has a ‘thrower that might satisfy the need for fire among the cautious though, because he’s created a remote control flamethrower.

Fuel for the flames is provided from a butane canister held within a 3D-printed frame, and is delivered via a piece of copper tube to a welding nozzle. A plunger beneath the can is connected to a rack-and-pinion driven by a servo, connected to a straightforward radio control receiver. The position of the can is adjusted until there is just enough gas to sustain a pilot flame at the nozzle, and a command to the servo releases a burst of gas that results in a satisfying puff of fire.

This is more of a static stage effect than the wearable flamethrowers or flamethrower guitar projects we’ve seen in the past, but it is no less a neat project. And unlike many other flamethrowers, it’s simple to build. We have to deliver the usual exhortation though: take care with your fire, we’d prefer not to be writing either obituaries of Fail Of The Week posts about smoking ruins.

Getting Good At FPGAs: Real World Pipelining

June 12, 2018 by 16 Comments

Parallelism is your friend when working with FPGAs. In fact, it’s often the biggest benefit of choosing an FPGA. The dragons hiding in programmable logic usually involve timing — chaining together numerous logic gates certainly affects clock timing. Earlier, I looked at how to split up logic to take better advantage of parallelism inside an FPGA. Now I’m going to walk through a practical example by modeling some functions. Using Verilog with some fake delays we can show how it all works. You should follow along with a Verilog simulator, I’m using EDAPlayground which runs in your browser. The code for this entire article is been pre-loaded into the simulator.

If you’re used to C syntax, chances are good you’ll be able to read simple Verilog. If you already use Verilog mostly for synthesis, you may not be familiar with using it to model delays. That’s important here because the delay through gates is what motivates us to break up a lot of gates into a pipeline to start with. You use delays in test benches, but in that context they mostly just cause the simulator to pause a bit before introducing more stimulus. So it makes sense to start with a bit of background on delays.

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Fail Of The Week: Two Rotors Are Not Better Than Four

June 12, 2018 by 20 Comments

Fair warning: [Paweł Spychalski]’s video is mostly him talking about how bad his “dualcopter” ended up. There are a few sequences of the ill-fated UAV undergoing flight tests, most of which seem to end with it doing a reasonable impression of a post-hole auger. We have to admit that it’s a pretty poor drone. But one can only truly fail if one fails to have some fun doing it, [Paweł] enjoyed considerable success, at least judging by the glee with which he repeatedly cratered the craft.

The overall idea seems to make sense, with coaxial props mounted in the middle of a circular 3D-printed frame. Mounted below the props are crossed vanes controlled by two servos. The vanes sit in the rotor wash and provide pitch and roll control, while yaw and thrust are controlled by varying the speeds of the counter-rotating props. [Paweł] knew going in that this was a sketchy aerodynamic design, and was surprised it performed as well as it did. But with ground effects limiting roll and pitch control close to the ground, the less-than-adequate thrust due to turbulence between the rotors, and the tendency for the center of mass and the center of gravity to get out whack with each other, all made for a joyously unstable and difficult to control aircraft.

Despite the poor performance, [Paweł] has plans for a Mark II dualrotor, a smaller craft with some changes based on what he learned. He’s no slouch at pushing the limits with multirotors, with 3D-printed racing quad frames and using LoRa for control beyond visual range. Still, we’re sure he’d appreciate constructive criticism in the comments, and we wish him luck with the next one.

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555 Ways To Speed Control A DC Motor

June 12, 2018 by 20 Comments

The 555 timer IC is a handful of active components all baked into one beautifully useful 8 pin package. Originally designed for timing purposes, they became ubiquitous parts that can achieve almost anything. In this case, they’re being used to create a  basic PWM motor controller.

The trick is to set the 555 up in astable mode, and use diodes and a potentiometer in the charge/discharge loop. By hanging a diode off either side of a potentiometer, leading to the charge and discharge pins, and connecting the center lug to the main capacitor, you can vary the resistance seen by the capacitor during charge and discharge. By making charging take longer, you increase the pulse width, and by making discharge take longer, you reduce the pulse width. The actual frequency itself is determined largely by the capacitor and total resistance of the potentiometer itself.

This is a very old-school way to generate a PWM signal, which could be used to vary intensity of a light or make noise on a buzzer. However, in this case, the output of the 555 is connected to a MOSFET which is used to vary the speed of a computer fan motor.

It’s an excellent way to learn about both PWM motor control and the use of 555 timers, all with a very low parts cost and readily available components. We’ve seen such setups before, used as easy-to-build dimmer switches, too.

Understanding A MOSFET Mixer

June 11, 2018 by 23 Comments

A mixer takes two signals and mixes them together. The resulting output is usually both frequencies, plus their sum and their difference. For example, if you feed a 5 MHz signal and a 20 MHz signal, you’d get outputs at 5 MHz, 15 MHz, 20 MHz, and 25 MHz. In a balanced mixer, the original frequencies cancel out, although not all mixers do that or, at least, don’t do it perfectly. [W1GV] has a video that explains the design of a mixer with a dual gate MOSFET, that you can see below.

The dual gate MOSFET is nearly ideal for this application with two separate gates that have effectively infinite input impedance. [Stan] takes you through the basic circuit and explains the operation in whiteboard fashion.

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A Close Eye On Power Exposes Private Keys

June 11, 2018 by 37 Comments

Hardware wallets are devices used exclusively to store the highly sensitive cryptographic information that authenticates cryptocurrency transactions. They are useful if one is worried about the compromise of a general purpose computer leading to the loss of such secrets (and thus loss of the funds the secrets identify). The idea is to move the critical data away from a more vulnerable network-connected machine and onto a device without a network connection that is unable to run other software. When designing a security focused hardware devices like hardware wallets it’s important to consider what threats need to be protected against. More sophisticated threats warrant more sophisticated defenses and at the extreme end these precautions can become highly involved. In 2015 when [Jochen] took a look around his TREZOR hardware wallet he discovered that maybe all the precautions hadn’t been considered.

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