Lighting Up A Very Wiry Candle

December 23, 2018 by Tom Nardi 4 Comments

Entries into the Circuit Sculpture Contest tend to be pretty minimalist by nature, and this LED candle by [Amal Mathew] is a perfect example. The idea here was to recreate the slim and uncomplicated nature of a real candle but with a digital twist, and we think he’s pulled it off nicely with a bare minimum part count and exaggerated wire length that gives it the look of a thin pillar candle.

To give the LED a fading effect, [Amal] uses a ATtiny85 programmed with the Arduino IDE. His code uses the analogWrite() in a loop to gradually increase and then decrease the PWM frequency. With the LED connected directly to one of the pins on the ATtiny85, the simple program achieves the fading effect without needing any additional components.

On the opposite side of the candle, connected by long copper wires, is the single CR2032 which provides power for the circuit. In a nice touch, [Amal] has turned the battery 90 degrees relative to the rest of the circuit, so it can serve as a weighted base. We imagine getting it to stand up might be a little fiddly from the looks of it, but once it’s up and merrily fading in and out, it really helps sell the candle idea.

The finished product might look fairly straight-forward, but in his write-up on Hackaday.io, [Amal] gives detailed instructions on how to build your own version if you’re not a bare microcontroller wizard. This includes direction on how to program the ATtiny85 using an Arduino Uno; a neat trick to know even if you aren’t planning on making any candles in the near future. The next logical step is making it so you can “blow out” the LED, which should only take the addition of a resistor and some updated code.

There’s still plenty of time to enter your own functional piece of art in the Circuit Sculpture Contest. Just write it up on Hackaday.io and submit it before the January 8th, 2019 deadline.

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A Plasma Speaker Using A TL494

August 5, 2018 by Jenny List 23 Comments

We’re used to loudspeakers as circular components with a paper cone and a big magnet inside which is suspended a coil that is connected to our audio amplifier. But moving-coil speakers are not the only way to create sound from electricity, there are one or two other weapons in the audio designer’s arsenal.

One of the more spectacular and entertaining is the plasma speaker, and it’s one [Marcin Wachowiak] has been experimenting with. A continuous plasma in the form of a discharge between two electrodes is modulated with an audio signal, and the resulting rapid changes in the volume of plasma creates a sound. The value of a plasma speaker lies in the exceptionally low size and mass of the element producing the sound, meaning that while it can only effectively reproduce high frequencies it can do so from a much closer approximation to a point source than can other types of tweeter. For this reason it’s beloved of some audiophiles, and you will find a few commercially produced plasma tweeters at the high-end of the audio market.

[Marcin] isn’t in it for the audiophilia, instead he’s interested in the properties of the plasma. His plasma speaker does do the job well though, and in particular he’s put a lot of thought into the design of its drive circuit. At its heart is the ubiquitous TL494 PWM controller that you may be more familiar with in the context of switching power supplies, this one applies the audio drive as PWM to the gate of a MOSFET that switches the primary of a flyback transformer. He’s added refinements such as a gate discharge circuit and a second primary winding with a freewheel diode.

The result is an effective plasma speaker. It’s difficult to judge from his YouTube video below the break whether he’s achieved audiophile purity, but happily that’s not the point. We’ve shown you a few other plasma speakers in our time, if the subject interests you then take a look at this rotating plasma vortex, or a version using a 555 timer.

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Junk Bin Spin Coater Uses Modded Case Fan

August 3, 2018 by Tom Nardi 4 Comments

We’ve all been there: you need a specific tool or gadget to complete a project, but it’s not the kind of thing you necessarily want to fork over normal retail price for. It could be something you’re only going to use once or twice, or maybe you’re not even sure the idea is going to work and don’t want to invest too much money into it. You cast a skeptical towards the ever-growing pile of salvaged parts and wonder…

Inspiration and a dig through the junk bin is precisely how [Nixie] built this very impressive spin coater for use in his ongoing homemade semiconductor project. If you’ve never had first hand experience with a spin coater, don’t worry, not many people have. Put simply, it’s a machine that allows the user to deposit a thin layer of material on a disc by way of centrifugal force. Just place a few drops in the center of the disc, then spin it up fast enough and let physics do the rest.

[Nixie] only needs to spin up a fairly tiny disc, and realized the hub of a 40x40mm brushless case fan was just about the perfect size. A quick pass through the lathe stripped the hub of its blades and faced off the front. Once he found a tube that was the exact same diameter of the fan’s axle, he realized he could even use a small vacuum pump to hold his disc in place. A proper seal is provided by 10 and 16 mm OD o-rings, installed into concentric grooves he machined into the face of the hub.

With a way to draw a vacuum through the hub of the spinner he just needed the pump. As luck would have it, he didn’t have to wait for one to make the journey from China, as he had one of those kicking around his junk bin from a previous project. The only thing he ended up having to buy was the cheap PWM fan controller which he mounted along with the modified fan to a piece of black acrylic; producing a fairly professional looking little piece of lab equipment. Check out the video after the break for a brief demonstration of it in action.

This isn’t the first specialized piece of gear [Nixie] has produced in his quest for DIY chips. We’ve previously covered his DIY tube oven as well as his vacuum chamber complete with magnetically controlled manipulator arm.

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Circuit VR: An (Almost) Practical Buck Converter

July 27, 2018 by Al Williams 9 Comments

In the last installment of Circuit VR, we walked around a simplified buck converter. The main simplification was using a constant PWM signal. The result is that the output voltage is a fixed fraction of the input voltage. For a regulator, the pulse width will need to depend on the output voltage so that any changes in the output are self-correcting. So this time, we’ll make a regulator, although we’ll still use a few Spice elements you’d have to replace in a practical design. In particular, we’ll assume you can generate a triangle wave, which is easy enough, and produce a stable 2.5 V reference.

The idea is to take a voltage reference and compare it to the output. We’ll think of the difference between the two as an error voltage, and use a comparator combined with a triangle wave generator to produce a PWM signal that is proportional to the error, and thus works to hold the output voltage constant.

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Arduino Powered Arcade Button Lighting Effects

July 20, 2018 by Tom Nardi 4 Comments

As if you already weren’t agonizing over whether or not you should build your own arcade cabinet, add this one to the list of compelling reasons why you should dedicate an unreasonable amount of physical space to playing games you’ve probably already got emulated on your phone. [Rodrigo] writes in to show off his project to add some flair to the lighted buttons on his arcade controller. (Google Translate)

The wiring for this project is about as easy as you’d expect: the buttons connect to the digital inputs on the Arduino, and the LEDs on the digital outputs. When the Arduino code sees the button getting pressed, it brings the corresponding LED pin high and starts a fade out timer using the SoftPWM library by [Brett Hagman].

It’s worth noting that the actual USB interface is being done with a stand-alone controller, so the Arduino here is being used purely to drive the lighting effects. The more critical reader might argue that you could do both with a single microcontroller, but [Rodrigo] was in a classic “Use what you’ve got” situation, and already had a USB controller on hand.

Of course, fancy lit arcade buttons won’t do you much good without something to put them in. Luckily we’ve covered some fantastic looking arcade cabinets to get you inspired.

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Behind The Pin: How The Raspberry Pi Gets Its Audio

July 13, 2018 by Jenny List 54 Comments

Single board computers have provided us with a revolution in the way we approach computing as hardware creators. We have grown accustomed to a world in which an entire microcomputer has become a component in its own right rather than a complex system, and we interface to them as amorphous entities through their exposed interfaces. But every pin or socket on a single board computer has something behind it, so following up on a recent news-inspired item in which we took a look at what lies behind the Ethernet jack on a Raspberry Pi, we’d like to continue that theme by looking behind more pins and interfaces. So today we’ll stay with the Raspberry Pi, and start with an easy target by taking a look down its audio jack.

All the main Raspberry Pi board releases since 2012 with the exception of the Pi Zero series, have featured a 3.5mm jack carrying line-level audio. The circuits are readily accessible via the Raspberry Pi website, and are easy enough to understand because of course all the really hard work is done within the silicon of the Broadcom system-on-chip. Looking at the audio circuitry, we’ll start by going back to the original Pi Model B from 2012 (PDF) because though more recent models have seen a few changes, this holds the essence of the circuitry.

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555 Ways To Speed Control A DC Motor

June 12, 2018 by Lewin Day 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.