What are the evocative sounds and smells of your childhood? The sensations that you didn’t notice at the time but which take you back immediately? For me one of them is the slight smell of phenolic resin from an older piece of consumer electronics that has warmed up; it immediately has me sitting cross-legged on our living room carpet, circa 1975.
That phenolic smell has gone from our modern electronics, not only because modern enclosures are made from ABS and other more modern plastics, but because the electronics they contain no longer get so hot. Our LCD TV for instance nowadays uses only 50 watts, while its 1970s CRT predecessor would have used several hundred. Before the 1970s you would not find many household appliances that used less than 100 watts, but if you take stock of modern electrical appliances, few use more than that. Outside the white goods in your kitchen and any electric heaters or hair dryers you may own, your appliances today are low-powered. Even your lighting is rapidly being taken over by LEDs, which are at their heart low-voltage devices.
There are many small technological advancements that have contributed to this change over the decades. Switch-mode power supplies, LCD displays, large-scale integration, class D audio and of course the demise of the thermionic tube, to name but a few. The result is often that the appliance itself runs from a low voltage. Where once you would have had a pile of mains plugs competing for your sockets, now you will have an equivalent pile of wall-wart power supplies. Even those appliances with a mains cord will probably still contain a switch-mode power supply inside.
“Chapter 5; Horowitz and Hill”. University students of all subjects will each have their standard texts of which everyone will own a copy. It will be so familiar to them as to be referred to by its author as a shorthand, and depending on the subject and the tome in question it will be either universally loathed or held onto and treasured as a lifetime work of reference.
For electronic engineers the work that most exemplifies this is [Paul Horowitz] and [Winfield Hill]’s The Art Of Electronics. It definitely falls into the latter category of course books, being both a mine of information and presented in an extremely accessible style. It’s now available in its third edition, but the copy in front of me is a first edition printed some time in the mid 1980s.
Chapter 5 probably made most of an impression on the late-teenage me, because it explains voltage regulation and power supplies both linear and switching. Though there is nothing spectacularly challenging about a power supply from the perspective of experience, having them explained as a nineteen-year-old by a book that made sense because it told you all the stuff you needed to know rather than just what a school exam syllabus demanded you should know was a revelation.
On the first page of my Art of Electronics chapter 5, they dive straight in to the μA723 linear voltage regulator. This is pretty old; a design from the legendary [Bob Widlar], master of analogue integrated circuits, which first made it to market in 1967. [Horowitz] and [Hill] say “Although you might not choose it for a new design nowadays, it is worth looking at in some detail, since more recent regulators work on the same principles“. It was 13 years old when they wrote that sentence and now it is nearly 50 years old, yet judging by the fact that Texas Instruments still lists it as an active product without any of those ominous warnings about end-of-life it seems plenty of designers have not heeded those words.
So why is a 50-year-old regulator chip still an active product? There is a huge range of better regulators, probably cheaper and more efficient regulators that make its 14-pin DIP seem very dated indeed. The answer is that it’s an incredibly useful part because it does not present you with a regulator as such, instead it’s a kit of all the parts required to make a regulator of almost any description. Thus it is both an astonishingly versatile device for a designer and the ideal platform for anyone wanting to learn about or experiment with a regulator. Continue reading “Get To Know Voltage Regulators with a 723”→
The PC power supply has been a standard of the junk box for the last couple of decades, and will probably continue to be for the foreseeable future. A product that is often built to a very high standard and which will give years of faithful service, yet which has a life of only a few years as the PC of which it is a part becomes obsolete. Over the decades it has evolved from the original PC and AT into ATX, supplying an ever-expanding range of voltage rails at increasing power levels. There have been multiple different revisions of the ATX power supply standard over the years, but they all share the same basic form factor.
So a pile of ATX supplies will probably feature in the lives of quite a few readers. Most of them will probably be old and obsolete versions of little use with today’s motherboards, so there they sit. Not small enough to ignore, yet Too Good To Throw Away. We’re going to take a look at them, try to work out what useful parts they contain, and see a few projects using them. Maybe this will provide some inspiration if you’re one of those readers with a pile of them seeking a purpose.
Does it ever just kill you that someone in a factory somewhere got to have all the fun of assembling your bench tools? There are a lot of questionable circuit boards floating around the Internet, and they can replicate practically any section of a circuit. When it comes to putting a prototype these days you can pretty much just buy each block of your system’s overview flowchart and string them together. [GreattScott!] combines a few of these into a relatively useful variable power supply with current limiting.
Admittedly, this is more of academic exercise if your only metric for success is monetary savings. Comparable power supplies can be purchased for the same amount of local currency as the parts in this build. However, there is something to be said for making it yourself.
The core of this build is based around the LTC3780, a bit of silicon from LT that offers both buck and boost converting along with a current control mode. It’s useful for a lot of things. The here is rated for up to 130 watts of power, which makes is a decent amount of power for a bench supply.
With a few modifications, like replacing the world’s most untrustworthy potentiometers and adding a nice ABS box, the build is completed. Along the way, [GreatScott!] offers a few tricks for testing and some reminders of how not to make yourself dead when playing with electricity.
The end is a working lab bench supply project that can easily keep a hacker entertained on a lazy Sunday afternoon.
A quality bench power supply is essential for electronics work. Nobody wants to go through the trouble of digging through their electronics bin just to find a wall wart with the right output. And, even if you were so inclined, it would be folly to assume that its output would actually be clean.
You could, of course, purchase a purpose-built bench power supply. But, this is Hackaday, and I’m sure many of you would rather build one yourself from an inexpensive PC power supply. Normally, you’d do this by separating out the different voltage lines into useful groups, such as 12V, 5V, and 3.3V. [Supercap2f] wanted to take this a step further, both to get a more useful unit and to practice his PCB-making.
His design uses a custom circuit design to fuse the circuits, and to provide some basic logic. Using the LCD display, you can see which lines are powered on. There is even a simple 3D printed cover to keep everything neat and tidy. [Supercap2f] has posted all of the design files, so you can build one of these yourself. We’ve seen similar builds in the past, but this is another nice one that anyone with the ability to etch PCBs can build.
[Csaba] and his friend bought a 600W switching lab-style power supply unit off eBay a while ago, and after about a year of tangled wires and mess, finally decided to enclose it in a fancy box.
The PSU itself required some modification as it was just a controller and a power board — so they added a dedicated mains transformer, and a buffer capacitor. The housing is made out of 3mm plywood which they designed and laser cut specifically for the PSU — and it looks fantastic.
It includes a cooling fan, a small digital display and a whole bunch of controls for finely tuning your electronics power requirement — take a look at the demonstration video after the break.
Everyone needs a power supply on their bench, but a standard lab supply isn’t cheap. [ludzinc]’s PSU Console is a cheap alternative, which provides the basic features you’d expect in a lab supply.
The basis of this PSU is a DC/DC module based on the LM2596 step down switching regulator. These modules cost less than a single LM2596, but have all the required components for a buck DC/DC converter. Sure, they might not last forever, and they’re not the most efficient regulators, but the price is right.
The front panel has four displays for voltage and current, which are just low cost voltmeter displays. The potentiometers are used for adjusting the voltage of the DC/DC, and controlling the current limiter. This limiter monitors current through a shunt, and shuts off a MOSFET when the limit is exceeded.
The final product looks like something that’s ready for daily use, and was much cheaper than most supplies with these features. These low cost DC/DC modules are worth a look if you’re considering a similar build.