Resistor: A passive chunk of material that resists the flow of electrical current. A terminal is connected to each end you’re done. What could be simpler?
It turns out it’s not so simple at all. Temperature, capacitance, inductance and other factors all play a part in making the resistor a rather complex component after all. Even its uses in circuits are many, but here we’ll just focus on the different types of fixed-value resistors, how they’re made, and what makes them desirable for different applications.
Let’s start with a simple one, and one of the oldest.
Continue reading “What Is There To Know About Resistors?”
If it wasn’t for the weird Dutch-Norwegian techno you’d presumably have to listen to forever, [Gianni B.]’s doll house for his daughter, [Rita] makes living in a Barbie World seem like a worthwhile endeavor. True to modern form, it’s got LED lighting. It’s got IoT. It’s got an app and an elevator. It even has a tiny, working, miniature television.
It all started with a Christmas wish. [Rita] could no longer stand to bear the thought of her Barbie dolls living a homeless lifestyle on her floor, begging passing toys for enough monopoly money to buy a sock to sleep under. However, when [Gianni] visited the usual suspects to purchase a dollhouse he found them disappointing and expensive.
So, going with the traditional collaborating-with-Santa ruse, he and his family had the pleasure of collaborating on a dollhouse development project. Each room is lit by four ultra bright LEDs. There is an elevator that’s controlled by an H-bridge module, modified to have electronic braking. [Rita] doesn’t own a Dr. Barbie yet, so safety is paramount.
The brain of the home automation is a PIC micro with a Bluetooth module. He wrote some code for it, available here. He also went an extra step and used MIT’s scratch to make an app interface for the dollhouse. You can see it work in the video after the break. The last little hack was the TV. An old arduino, an SD Card shield, and a tiny 2.4 inch TFT combine to make what’s essentially a tiny digital picture frame.
His daughter’s are overjoyed with the elevation of their doll’s economic class and a proud father even got to show it off at a Maker Faire. Very nice!
Continue reading “Rita’s Dolls Probably Live Better Than You Do”
The Apollo program is a constant reminder that we just don’t need so much to get the job done. Sure it’s easier with today’s tools, but hard work can do it too. [Bill Hammack] elaborates on one such piece of engineering: The Alignment Optical Telescope.
The telescope was used to find the position of the Lunar Module in space so that its guidance computer could do the calculations needed to bring the module home. It does this using techniques that we’ve been using for centuries on land and still use today in space; although now it’s done with computer vision. It was used to align the craft to the stars. NASA used stars as the fixed reference points for the coordinate system used to locate objects in space. But how was this accomplished with great precision?
The alignment optical telescope did this by measuring two unknowns needed by the guidance computer. The astronaut would find the first value by pointing the telescope in the general area necessary to establish a reading, then rotate the first reticle (a horizontal line) on the telescope until it touched the correct star. A ring assembly was then adjusted, moving an Archimedes spiral etched onto the viewfinder. When the spiral touches the star you can read the second value, established by how far the ring has been rotated.
If you’ve ever seen the Lunar Module in person, your first impression might be to giggle a bit at how crude it is. The truth is that much of that crudeness was hard fought to achieve. They needed the simplest, lightest, and most reliable assembly the world had ever constructed. As [Bill Hammack] states at the end of the video, breaking the complicated tool usually used into two simple dials is an amazing engineering achievement.
Continue reading “Apollo: The Alignment Optical Telescope”