555

111 Articles

A Capacitive Soil Sensor Hack For Lower Voltage Supplies

July 27, 2019 by 22 Comments

A frequent beginner project involves measuring soil moisture levels by measuring its resistance with a couple of electrodes. These electrodes are available ready-made as PCBs, but suffer badly from corrosion. Happily there is a solution in the form of capacitive sensor probes, and it is these that [Electrobob] is incorporating in to a home automation system. Unfortunately the commercial capacitive probes are designed to run from a 3.3 V supply and [Bob]’s project is using a pair of AA cells, so a quick hack was needed to enable them to be run from the lower voltage.

The explanation of the probe’s operation is an interesting part of the write-up, unexpectedly it uses a 555 configured as an astable oscillator. This feeds an RC low pass filter of which the capacitor is formed by the soil probe, which in turn feeds a rectifier to create a DC output. This can be measured to gain a reading of the soil moisture level.

The probe is fitted with a 3.3 V LDO regulator, which is simply bypassed. Measurements show its output to be linear, so if the supply voltage is also measured an accurate reading can be gleaned. These probes are still a slightly unknown quantity to many who might find a use for them, so it’s extremely useful to be given this insight into them.

Hackaday Podcast Ep24: Mashing Smartphone Buttons, Sound Blastering, Trash Printing, And A Ludicrous Loom

June 21, 2019 by 1 Comment

Hackaday Editors Elliot Williams and Mike Szczys wade through the fun hacks of the week. Looks like Google got caught ripping off song lyrics (how they got caught is the hack) and electric cars are getting artificially noisier. We look at 3D Printing directly from used plastic, and building a loom with many hundreds of 3D printed parts. The Sound Blaster 1.0 lives again thanks to some (well-explained) reverse engineered circuitry. Your smartphone is about to get a lot more buttons that work without any extra electronics, and we’ll finish things up with brass etching and downloadable nuclear reactor plans.

Take a look at the links below if you want to follow along, and as always tell us what you think about this episode in the comments!

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A Baby Named DJ

June 19, 2019 by 8 Comments

Some of us are guilty of picking up questionable hardware from garage sales, fleamarkets, and well-meaning relatives. There is a balance between turning down a good investment and hoarding, and if we figure out how to tell the difference you will be the first to know. [Clem Mayer] may start on the side of unwise acquisition, but he pushes a broken fetal detector into the realm of awesome by converting it to an analog synthesizer, born to headline at an Eastern European dance party.

He starts with a basic teardown, and we get to see how old hardware was serviceable with only two standard screws. It is a good thing too, because the nickel-cadmium batteries are older than some of you and they are in need of replacement. New nickel-metal hydride batteries got it up and running but [Clem] does not have a baby bump so its functionality turned to Pink Floyd era synthesizer circuit bending. Circuit bending involves modifying a circuit for sound it was not intended to make.

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Hackaday Podcast Ep14: Keeping Raspberry’s SD Card Alive, We Love MRRF, And How Hot Are Flip Chips?

April 12, 2019 by No comments

Elliot Williams and Mike Szczys take a look at advances in photogrammetry (building 3D models out of many photographs from a regular camera), a delay pedal that’s both aesthetically and aurally pleasing, and the power of AI to identify garden slugs. Mike interviews Scotty Allen while walking the streets and stores of the Shenzhen Electronics markets. We delve into SD card problems with Raspberry Pi, putting industrial controls on your desk, building a Geiger counter for WiFi, and the sad truth about metal 3D printing.

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

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An Even Smaller World’s Smallest LED Blinky

April 11, 2019 by 14 Comments

Everything can be done with a 555. It’s a universal law, as all readers know. And a flashing light, you might think, will have been done before many times. But nobody has ever created a 555 flashing light as small as thie one created by [TWires], who has taken a TI LMC555 chip-scale packaged 555 and dead-bugged a working flasher on its surface using 01005 discrete components. There is a video showing it in operation that we’ve placed below the break, and it’s tiny. We probably all consider ourselves to be quite good at soldering, but this piece of work is in another class entirely.

The project was inspired by [Mike Harrison]’s previous holder of the smallest blinky prize, which used a PIC microcontroller atop a tiny surface mount supercapacitor. It uses the same capacitor for power, but we’d say it’s taken the blinky to new levels of tininess. Does this mean a new arms race is upon us in the world of tiny blinkies? We hope so, and though it’s difficult to imagine they can get much smaller we can’t wait to see what people come up with. If there’s one thing about our community it’s that saying something can’t be done is unwise: one of you will find a way if it is at all possible. Even Microchip’s MIC1555 might be a bit big though, so something inventive is called for.

For a fascinating run-down of the state of the 555 art, read this article from our own [Ted Yapo].

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Fizzle Loop Synth Does It With 555 Timers

April 5, 2019 by 9 Comments

For every project that uses an Arduino to make soup or an ESP8266 to hash bitcoin, there’s always someone out there uttering the same old refrain. I could have done it with a 555. More often than not, this is true, even if it is tangential to the discussion being had. In this case however, such a statement is moot. [lonesoulsurfer] has built the Fizzle Loop Synth, featuring not one, but three triple-nickel timers.

It’s a build that delights in both presentation and performance. The hardware is elegantly slotted into a vintage metal flashlight case, which is absolutely covered in controls. It’s an aesthetic that gives us an irresistible urge to start twiddling knobs and flicking switches. Inside, two 555s are set up as basic flasher circuits, each feeding a vactrol – essentially a resistive optoisolater. Inside is an LED, which is optically coupled to a light-dependent resistor. The LEDs are flashed by the 555s, and this creates a varying resistance which is used to feed a third 555 which generates the tones.

The final result is a fun little noisebox that’s capable of generating quite the variety of bleeps, bloops and blops. There’s an onboard speaker for noodling on the go, as well as a line-out if you need to record your work on external hardware. It would be great fun to hear this circuit hooked up to a modular synth, too.

For a history lesson on the venerable 555, we’ve got you covered. Video after the break.

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The Three Faces Of The 555

April 3, 2019 by 35 Comments

In these days of cheap microcontrollers, it is hard to remember there was a time when timing things took real circuitry. Even today, for some applications it is hard to beat the ubiquitous 555 timer IC. It is cheap, plentiful, and reliable. What’s interesting about the 555 is it isn’t so much a dedicated chip as a bunch of building blocks on a chip. You can wire those building blocks up in different ways to get different effects, and [learnelectronics] has a video showing the three major modes you typically see with the 555: astable, bistable, and monostable.

The 555 is really only a few comparators, a voltage divider, one or two transistors, a flip flop and an inverter. The idea is you use a capacitor to charge and the comparators can set or reset the flip flop in different ways. A reset input or the flip flop can turn on the transistor to discharge the capacitor.

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