555

164 Articles

Pushing The Plasma Limits With A Custom Flyback Transformer

October 22, 2024 by 18 Comments

For serious high-voltage plasma, you need a serious transformer. [Jay Bowles] from Plasma Channel is taking his projects to the next level, so he built a beefy 6000:1 flyback transformer.

[Jay] first built a driving circuit for his dream transformer, starting with a simple 555 circuit and three MOSFETs in parallel to handle 90 A of current. This led to an unexpected lesson on the necessity for transistor matching as one of them let out the Magic Smoke. On his second attempt, the 555 was swapped for an adjustable pulse generator module with a display, and a single 40 A MOSFET on the output.

The transformer is built around a large 98×130 mm ferrite core, with eleven turns on the primary side. All the hard work is on the secondary side, where [Jay] designed a former to accommodate three winding sections in series. With the help of the [3D Printing Nerd], he printed PLA and resin versions but settled on the resin since it likely provided better isolation.

[Jay] spent six hours of quality time with a drill, winding 4000 feet (~1200 m) of enameled wire. On the initial test of the transformer, he got inch-long arcs on just 6 V and 15 W of input power. Before pushing the transformer to its full potential, he potted the secondary side in epoxy to reduce the chances of shorts between the windings.

Unfortunately, the vacuum chamber hadn’t removed enough of the air during potting, which caused a complete short of the middle winding as the input started pushing 11 V. This turned the transformer into a beautiful copper and epoxy paperweight, forcing [Jay] to start again from scratch.

On the following attempt [Jay] took his time during the potting process, and added sharp adjustable electrodes to act as voltage limiters on the output. The result is beautiful 2.25-inch plasma arcs on only 11 V and 100 W input power. This also meant he could power it with a single 580 mAh 3S LiPo for power.

[Jay] plans to use his new transformer to test materials he intends to use in future plasma ball, ion thruster, and rail gun projects. We’ll be keeping an eye out for those!

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Humble 555 Gets A Boost For ESR Meter

September 4, 2024 by 6 Comments

[Peter Demchenko] wanted to use a low power TS555 in an ESR meter design. The problem is, he needed to handle significant current sink requirements for cases where the capacitor under test had a low ESR. The TS555 wasn’t up to the task.

However, [Peter] made an interesting observation. the output pin of the device can sink or source current. However, the discharge pin is exactly the same output but can only sink current.

But what if you tied them together? Using some equalizing resistors, that’s exactly what he did, and this roughly doubles the rated current sink capability. According to [Peter], you do make the circuit more sensitive to power supply variations, but that could be an acceptable trade, depending on your application.

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The 555 As A MOSFET Driver

August 5, 2024 by 25 Comments

To drive a MOSFET requires more than merely a logic level output, there’s a requirement to charge the device’s gate which necessitates a suitable buffer amplifier. A variety of different approaches can be taken, from a bunch of logic buffers in parallel to a specialised MOSFET driver, but [Mr. T’s Design Graveyard] is here with a surprising alternative. As it turns out, the ever-useful 555 timer chip does the job admirably.

It’s a simple enough circuit, the threshold pin is pulled high so the output goes high, and the PWM drive from an Arduino is hooked up to the reset pin. A bipolar 555 can dump a surprising amount of current, so it’s perfectly happy with a MOSFET. We’re warned that the CMOS variants don’t have this current feature, and he admits that the 555 takes a bit of current itself, but if you have the need and a 555 is in your parts bin, why not!

This will of course come as little surprise to anyone who played with robots back in the day, as a 555 or particularly the 556 dual version made a pretty good and very cheap driver for small motors. If you’ve ever wondered how these classic hips work, we recently featured an in-depth look.

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A Modchip For A Fridge

July 21, 2024 by 51 Comments

An annoying fridge that beeps incessantly when the door is open too long should be an easy enough thing to fix by disconnecting the speaker, but when as with [kennedn]’s model it’s plumbed in and the speaker is inaccessible, what’s to be done? The answer: create a mod chip for a fridge.

While the fridge electronics themselves couldn’t be reached, there was full access to a daughterboard with the fridge controls. It should be easy enough to use them to turn off the alarm, but first a little reverse engineering was required. It used a serial communication with an old-school set of shift registers rather than a microcontroller, but it soon became apparent that the job could be done by simply pulling the buttons down. In a move that should gladden the heart of all Hackaday readers then, the modchip in question didn’t even have to be a processor, instead it could be the venerable 555 timer. Our lives are complete, and the fridge is no longer annoying.

The 555 is unashamedly a Hackaday cliche, but even after five decades it still bears some understanding.

Why The 555 Is Not A Timer, But Can Be One

July 11, 2024 by 31 Comments

Although commonly referred to as a ‘timer IC’, the venerable NE555 and derivatives are in fact not timer ICs. This perhaps controversial statement is the open door that gets kicked in by [PKAE Electronics] over at YouTube, as he explains with excellent diagrams and simulations how exactly these ICs work, and what it takes to make it actually do timer things. For anyone who has ever used one of these chips there is probably nothing too mind-blowing, but it’s an infinitely better way to wrap your way around an NE555 and kin than a datasheet.

At its core, the 555 contains three 5 kOhm resistors as a voltage divider, which has been incorrectly postulated to be the source of the chip’s name. This voltage divider controls two comparators, which in turn control an SR flipflop. These comparators are used for the voltage trigger and threshold inputs, which in turn toggle the flipflop, respectively setting and resetting it. This by itself just means that the 555 can be used as a threshold detector, with settable control voltage. How a 555 becomes a timer is when the discharge, trigger and threshold pins are combined with external resistors and a capacitor, which creates a smooth square wave on the 555’s output pin.

There are many ways to make basic components into an oscillator of some type, but the 555 is a great choice when you want something more refined that doesn’t involve using an entire MCU. That said, there’s far more that the 555 can be used for, as [PKAE] alludes to, and we hope that he makes more excellent videos on these applications.

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A 555-Shaped Discrete Component 555

March 11, 2024 by 2 Comments

While the “should have used a 555” meme is strong around these parts, we absolutely agree with [Kelvin Brammer]’s decision to make this 555-shaped plug-in replacement for the 555 timer chip using discrete parts, rather than just a boring old chip.

As [Kelvin] relates, this project started a while back as an attempt to both learn EDA and teach students about the inner workings of the venerable timer chip. The result was a 555-equivalent circuit on a through-hole PCB, with the components nicely laid out into the IC’s functional blocks. As a bonus, the PCB was attached to an 8-pin header which could be plugged right in as a direct replacement for the chip.

Fast forward a few years, and [Kelvin] needed to learn yet another EDA package; what better way than to repeat the 555 project? It was also a good time to step into SMD design, as well as add a little zazzle. While the updated circuit isn’t as illustrative of the internal arrangement of the 555, the visual celebration of the “triple nickel” is more than worth it. And, just like the earlier version, this one has a header so you can just plug and chug — with style.

Want to know how the 555 came to be? We’ve covered that. You can also look at some basic 555 circuits to put your 555-shaped 555 to work. We’ve even seen a vacuum tube 555 if that’s more your thing.

Back To Basics With A 555 Deep Dive

February 17, 2024 by 28 Comments

Many of us could sit down at the bench and whip up a 555 circuit from memory. It’s really not that hard, which is a bit strange considering how flexible the ubiquitous chip is, and how many ways it can be wired up. But when was the last time you sat down and really thought about what goes on inside that little fleck of silicon?

If it’s been a while, then [DiodeGoneWild]’s back-to-basics exploration of the 555 is worth a look. At first glance, this is just a quick blinkenlights build, which is completely the point of the exercise. By focusing on the simplest 555 circuits, [Diode] can show just what each pin on the chip does, using an outsized schematic that reflects exactly what’s going on with the breadboarded circuit. Most of the demos use the timer chip in free-running mode, but circuits using bistable and monostable modes sneak in at the end too.

Yes, this is basic stuff, but there’s a lot of value in looking at things like this with a fresh set of eyes. We’re impressed by [DiodeGoneWild]’s presentation; while most 555 tutorials focus on component selection and which pins to connect to what, this one takes the time to tell you why each component makes sense, and how the values affect the final result.

Curious about how the 555 came about? We’ve got the inside scoop on that.

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