Build Your Own LAN Cable Tester

Sure, you can buy a cable tester, but what fun is that? [Ashish] posted a nice looking cable tester that you can build with or without an onboard Arduino. If you don’t use an Arduino, the project uses a 555 chip to test the eight wires in an Ethernet cable. The readout is simple. When testing a conductor, one of 8 LEDs will light. If one doesn’t light, the cable is open. If more than one light up, there is a short. Mixed up pins will cause the LEDs to light out of sequence. You can see the device in the video below.

The 555 device is fine for the design and we were surprised that the project had provisions for using an Arduino as nothing more than a pulse generator. It could replace most of the circuit which is pretty simple. A decade counter converts the pulses into 8 pulses (a wiring change makes it reset on the 9th count). The rest of the circuit is nothing more than LEDs, resistors, and diodes.

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Minimal Blinky Project Makes The Chip The Circuit Board

We’ve got a thing for projects that have no real practical value but instead seek to answer a simple yet fundamental question: I wonder if I can do that? This dead-bug style 555 blinky light is one of those projects, undertaken just to see how small a circuit can be. Pretty small, as it turns out, and we bet it can get even smaller.

[Danko]’s minimal circuit is about as small as possible for the DIP version of the venerable 555 chip. The BOM is stripped to the bone: just the chip, three resistors, a capacitor, and an LED. All the discrete components are SMDs in 0805. The chip’s leads are bent around the package to form connections, and the SMDs bridge those “traces” to complete the circuit. [Danko] shows the build in step-by-step detail in the video below. There’s some fairly fine work here, but we can’t help wondering just how far down the scale this could be pushed. We know someone’s made a smaller blinky using a tiny microcontroller, but we’d love to see this tried with the BGA version of the chip which is only 1.4 mm on a side.

Cheers to [Danko] for trying this out and having some fun with an old chip. He seems to have a bit of a thing for the 555; check out this cute robot sculpture that’s built around the chip.

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555 Timer Robots Will Rule The World

A running joke we see in the comments by Hackaday readers whenever a project includes an Arduino or Raspberry Pi that seems like overkill is to proclaim that “I could have done it with a 555 timer!” That’s especially the case if the project amounts to a blinking light or anything which oscillates. Well [Volos Projects] has made a whole robot out of a 555 timer circuit.

Okay, it’s really a dead bug circuit in the shape of a robot but it does have blinking lights. We also like how the base is the battery, though some unevenness under it seems to make the whole thing a bit unstable as you can see in the video below. There are also a few parts which are cosmetic only. But it’s cute, it’s a 555 timer circuit, and it’s shaped like a robot. That all makes it a win.

We do wonder how it can be taken further. After all, a walk cycle is a sort of oscillation so the 555 timer circuit could run some servo motors or at least some piezoelectric feet. Ideas anyone?

On the other hand, if you’re looking for a dead bug circuit which belongs in a fine arts museum then you need look no further than The Clock.

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Electronic ColorChord Turns Color Into Sound

[Dr. Cockroach] has delighted us again with another of his circuits on cardboard. He calls it steampunk inspired, and while we guess we can see what he’s getting at, it’s more like a sweet example of artful dead bug construction. He calls it the ColorChord. Point its photo cells at a color and it’ll play a tone or a combination of tones specific to that color.

Three 555-centric boards use thumbtacks as connection points which he solders to, the same technique he used for his cardboard computer. They provide simple tones for red, green, and blue and a mix for any other color. However, he found that the tones weren’t distinguishable enough for similar colors like a bright sun yellow and a reddish yellow. So he ended up pulsing them using master oscillator, master-slave flip-flop, and sequencer circuits, all done dead bug style.

We’re not sure how practical it is but the various pulsed tones remind us of the B space movies of the 1950s and 60s. And as for the look of it, well it’s just plain fun to look at. Hear and see it for yourself in the video below.

And if you want to see some dead bug circuitry as high art then check out this awesome LED ring, this sculptural nixie clock, and perhaps the most wondrous of all, The Clock.

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555 Ways to Speed Control A DC Motor

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.

NES Controller Slider-Based Light Theremin

Having never use a 555 before, [lonesoulsurfer] decided that his first foray into the world’s most popular and versatile IC would be to use a 555 to make beautiful chiptunes. For that, we commend him. He found [Dean Segovis]’ Slidersynth light-based Theremin and got to work building his own version it and stuffing it into a (knockoff!) NES controller.

For the uninitiated, a Theremin is a touch-less synthesizer that uses human capacitance and a pair of antennae to control oscillation and amplitude. In a light-based Theremin such as this one, the oscillation is controlled by the intensity of photons from a white LED and their interaction with a light-dependent resistor, also known as a photocell or ‘squiggly resistor’.

The oscillations themselves are created by wiring up the 555 as an astable oscillator, and the pitch is controlled with a potentiometer mounted on the back. It has a small built-in speaker, but [lonesoulsurfer] replaced the B button with a 3.5 mm audio jack so he can plug it into a powered speaker and really rock out. We’ve got his demo tape queued up after the break.

We love pocket instruments around here. If you prefer brass and woodwinds, this pocket woodwind MIDI controller just might draw your lips into an O.

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Learning The 555 From The Inside

One way to understand how the 555 timer works and how to use it is by learning what the pins mean and what to connect to them. A far more enjoyable, and arguably a more useful way to learn is by looking at what’s going on inside during each of its modes of operation. [Dejan Nedelkovski] has put together just such a video where he walks through how the 555 timer IC works from the inside.

We especially like how he immediately removes the fear factor by first showing a schematic with all the individual components but then grouping them into what they make up: two comparators, a voltage divider, a flip-flop, a discharge transistor, and an output stage. Having lifted the internals to a higher level, he then walks through examples, with external components attached, for each of the three operating modes: bistable, monostable and astable. If you’re already familiar with the 555 then you’ll enjoy the trip down memory lane. If you’re not familiar with it, then you soon will be. Check out his video below.

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