Control System Fundamentals by Video

If you’ve had the classic engineering education, you probably have a hazy recollection of someone talking about control theory. If you haven’t, you’ve probably at least heard of PID controllers and open loop vs closed loop control. If you don’t know about control theory or even if you just want a refresher, [Brian Douglas] has an excellent set of nearly 50 video lectures that will give you a great introduction to the topic. You can watch the first lecture, below.

You might think that control systems are only useful in electronics when you are trying to control a process like a chemical plant or a temperature. However, control theory shows up in a surprising number of places from filters to oscillators, to the automatic gain control in a receiver. You’ll find the background behind many familiar results inside control theory. Sort of like when you take calculus and you discover how they came up with all the formulas you memorized in geometry.

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Lock In Amplifiers

If you have about an hour to kill, you might want to check out [Shahriar’s] video about the Stanford Research SR530 lock in amplifier (see below). If you know what a lock in amplifier is, it is still a pretty interesting video and if you don’t know, then it really is a must see.

Most of the time, you think of an amplifier as just a circuit that makes a small signal bigger in some way — that is, increase the voltage or increase the current. But there are whole classes of amplifiers designed to reject noise and the lock in amplifier is one of them. [Shahriar’s] video discusses the math theory behind the amplifier, shows the guts, and demonstrates a few experiments (including measuring the speed of sound), as well.

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Scooter Wheels Keep DIY Barn Doors on Track

[MotoGeeking] built a giant spray booth and is in the process of making customized, air-filtering barn doors for it. When it came to buy hardware to move the doors, though, he found all the ready-made options to be prohibitively expensive. You know what comes next: he designed barn door hardware from the ground up, and did it as cheaply as possible.

After intensely studying many images of barn doors and hardware, [MotoGeeking] decided on the right wheels and went from there. Kick scooter wheels fit the bill nicely, since they are designed to support a lot of weight and come with their own bearings and spacers. And they’re cheap, too — just $9 for a pair.

[MotoGeeking] found some C channel extruded aluminium that seemed to be a perfect match for the wheels, but the wheel was quick to bind whenever it touched the sides. He solved that one by epoxying a length of round bar into the bottom corners. This allows the wheel to move freely while forcing it to stay centered in the track.

In designing the 1/4″ aluminium brackets, [MotoGeeking] took a measure thrice, order once approach to selecting the fasteners. You probably know by now that McMaster-Carr has free CAD drawings for every little thing. [MotoGeeking] imported the ones he liked into Illustrator and built around them. This helped him get it right the first time and kept the headaches and hair-tearing away. Watch the giant door skeleton glide effortlessly on its track after the break.

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Spray Paint Goes DIY Virtual with a Vive Tracker

Here is a virtual spray painting project with a new and DIY twist to it. [Adam Amaral]’s project is an experiment in using the Vive Tracker, which was released earlier this year. [Adam] demonstrates how to interface some simple hardware and 3D printed parts to the Tracker’s GPIO pins, using it as a custom peripheral that is fully tracked and interactive in the Vive’s VR environment. He details not only the custom spray can controller, but also how to handle the device on the software side in the Unreal engine. The 3D printed “spray can controller” even rattles when shaken!

There’s one more trick. Since the Vive Tracker is wireless and completely self-contained, the completed rattlecan operates independently from the VR headset. This means it’s possible to ditch the goggles and hook up a projector, then use the 3D printed spray can to paint a nearby wall with virtual paint; you can see that part in action in the video embedded below.

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LEGO Prototyping with Tinkercad’s Brick Mode

[Andrew Sink] made a brief video demonstrating how he imported an STL of the well-known 3D Benchy tugboat model, and instead of sending it to a 3D printer used the Brick Mode feature to make a physical copy out of LEGO bricks in an eye-aching kaleidoscope of colors.

For those of you who haven’t used Tinkercad lately, Brick Mode allows you to represent a model as LEGO bricks at various scales. You model something as usual (or import a model) and by pushing a single button, render it in LEGO as accurately as can be done with standard bricks.

In addition, [Andrew] shows how the “Layers” feature can be used as a makeshift assembly guide for the model, albeit with a couple of quirks that he explains in the video embedded below.

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PocketCHIP As A Hardware Hacker’s Terminal

Conferences these days can be tricky places to be at – especially hardware and hacker cons. If you aren’t the one doing the hacking, then you can be sure your devices are being probed, pinged and possibly, hacked. It certainly isn’t the place to bring your precious laptop. Besides, as the day wears on and your feet start aching, regular laptops start feeling bigger and heavier. What you need is a burner laptop – one that is lightweight, cheap and that you don’t mind getting hacked. [dalmoz] wrote a short, to-the-point, tutorial on making use of PocketCHIP as a hardware-hacker’s best friend when it comes to UART connections. It’s also handy to use as a stand alone serial monitor for your projects without having to dedicate a USB port and screen real estate.

The PocketCHIP is a dock for the C.H.I.P. microcomputer and adds a LED backlit touchscreen display, QWERTY keyboard and LiPo battery in a lightweight, molded case. For $70, you get a 1 GHz ARM v7 processor, 512MB RAM, Mali 400 GPU, WiFi and Bluetooth. It’s light enough to be hung around your neck via its lanyard slot. And all of the GPIO pins are conveniently broken out, including the UART pins. Right now, it’s in the hands of Kickstarter backers, but the Next Thing Co website indicates availability sometime this month.

On the hardware side, all you need to do is add header pins to TX, RX and GND (and maybe 5 V and 3 V if required) on the PocketCHIP GPIO header and you’re good to go. On the software side, things are equally easy. The UART pins are meant to provide debug access to the CHIP itself and need to be released from internal duty. Once the UART port is identified, a single terminal command frees its status as a debugging interface. After that, use any terminal emulator – [dalmoz] recommends Minicom – and you’re all set. In the unlikely event that all you have is an Arduino lying around, [dalmoz] posted a simple sketch that can be used to make sure you have it working. Great hacking tip, ’cause it is as simple as it gets. If you’d like to know more about the CHIP project, check out its documentation and Github repository – it’s all open source.

Switching: from Relays to Bipolar Junction Transistors

How many remote controls do you have in your home? Don’t you wish all these things were better integrated somehow, or that you could add remote control functionality to a random device? It’s a common starting point for a project, and a good learning experience for beginners.

A common solution we’ve seen applied is to connect a relay in parallel to all the buttons we want to press. When the relay is triggered, for example by your choice of microcontroller, it gets treated as a button press. While it does work, relays are not really the ideal solution for the very low current loads that we’re dealing with in these situations.

As it turns out, there are a few simple ways to solve this problem. In this article, we’re going to focus on using common bipolar junction transistors instead of relays to replace physical switches. In short, how to add transistors to existing electronics to control them in new ways.

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