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A revolutionary current clamp engineered for powerful performance and unmatched portability.
Pokit Innovations
All types of resistors have their own resistor symbols which are used when a circuit diagram is drawn. This page will explain the different standards which are used for resistor symbols and display the most common symbols.
Have you ever turned on a transformer and heard a loud humming sound? What about having a blown fuse or tripped circuit breaker? These signs can all indicate transformer inrush current.
Transformer inrush current describes a spike in current that occurs when you initially turn on your transformer. This spike can be up to 10 times higher than normal current. Why does inrush current occur? It can happen because large transformers demand a huge amount of current when energized. Until the inductive resistance and magnetic field builds, they essentially act as short circuits. //
What is a practical solution to this problem? One convenient way to limit inrush current in a transformer is by using an NTC thermistor. The photo below shows an NTC thermistor placed in the circuit board to provide optimal inrush protection (Figure 2).
Transformer inrush current limiter in circuit
Figure 2: The NTC thermistor is placed in series with the input line to limit inrush current in a transformer.
Transformer Inrush Current Calculation
Here at Ametherm, we have a calculation that we use to help our customers select the right NTC thermistor part number. We thought we would share this with you so you can do the math for yourself, if you feel so inclined.
The 7 step process below will walk you through the calculation we performed for a 40VA transformer. You can apply these calculations to your own transformer as well.
How do I Select the Right Inrush Current Limiter for My Application?
Inrush current limiters are designed with different characteristics like resistance versus temperature curve to accommodate numerous applications. Because of this, it is necessary to make some calculations based on your system requirements to select the best inrush current limiter for your needs.
If the AC wave is going through its zero value, the current drawn will be very high and exceed the saturation current (Figure 1). In this situation, transformer inrush current protection becomes necessary to keep the transformer functioning properly.
Transformer inrush current wave
Figure 1: A transformer draws inrush current that can exceed saturation current affecting the magnetic property of the core.
Solution to Transformer Inrush Current
What is a practical solution to this problem? One convenient way to limit inrush current in a transformer is by using an NTC thermistor.
A time delay circuit, consisting of a relay and timer, can be employed to take the inrush current limiter out of the circuit as soon as the inrush current has passed through, allowing the inrush current limiter to begin to cool down much sooner. A great example of how this is done can be found at instructables.com, showing how to create this time delay when the inrush current limiter needs a little rest.
Large transformers have a huge current demand when they are initially turned on. This is because, until the magnetic field and inductive resistance builds, they are essentially short circuits. For example, you may have turned on some large tool or appliance and heard an initial large "HUMMMMMMM". That is the transformer say "Ow". The circuit breaker for that outlet might also go "Whoa, what are you doing!"
The transformer above (Avel Y236907 800VA 45V+45V Toroidal Transformer), for example, will try to draw over 100 Amps on the first cycle of 60 Hz Power.
To keep a large transformer from being damaged at turn-on (and to keep it from saying "ow"), or to keep a breaker from popping, you put in an inrush current limiter circuit. This Instructable will detail how to do that.
Making an oscilloscope is relatively easy, while making a very fast oscilloscope is hard. There’s a trick that converts a mundane instrument into a very fast one, it’s been around since the 1950s, and [CuriousMarc] has a video explaining it with an instrument from the 1960s. The diode sampler is the electronic equivalent of a stroboscope, capturing parts of multiple cycle of a waveform to give a much-slowed-down representation of it on the screen. How it works is both extremely simple, and also exceptionally clever as some genius-level high-speed tricks are used to push it to the limit. We’ve put the video below the break.
[Marc] has a Keysight 100 MHz ‘scope and the sampler allows him to use it to show 4 GHz. Inside the instrument is a pair of sample-and-hold circuits using fast diodes as RF switches, triggered by very low-rise-time short pulses. Clever tricks abound, such as using the diode pair to cancel out pulse leakage finding its way back to the source. To complete this black magic, an RF-tuned stub is utilized to help filter the pulses and further remove slower components.
It’s thus interesting on more than one level to find a promotional film from the mid 1970s showcasing VEB Fernsehgerätewerk Stassfurt (German, Anglophones will need to enable subtitle translation), the factory which produced televisions for East Germans. It provides a pretty comprehensive look at how a 1970s TV set was made, gives us a gateway into the East German consumer electronics business as a whole, and a chance to see how the East Germany preferred to see itself. https://www.youtube.com/watch?v=P0xMK6UZBys //
The film is at pains to talk about the factory as a part of the idealised community of a socialist state, and we’re given a tour of the workers’ facilities to a backdrop of some choice pieces of music. References to the collective and some of the Communist apparatus abound, and finally we’re shown the factory’s Order of Karl Marx. As far as it goes then we Westerners finally get to see the lives of each genosse, but only through an authorised lens.
The TVs made at Stassfurt were sold under the RFT East German technology combine brand, and the factory continued in operation through the period of German re-unification. Given that many former East German businesses collapsed with the fall of the Wall, and that the European consumer electronics industry all but imploded in the period following the 1990s then, it’s something of a surprise to find that it survives today, albeit in a much reduced form. The plant is now owned by the German company TechniSat, and manufactures the latest-spec digital TVs. //
As a juxtaposition of how a communist TV factory saw itself, have a watch of a capitalist one doing a bit of self-promotion.
https://hackaday.com/2017/12/29/retrotechtacular-1950s-televisions-were-beasts/#more-287834
Symbols of Electronic Sensors / Transducers / Detectors
How the neon-filled glow lamps came to hold a special place in enthusiasts’ hearts
UPDATE 18 JAN. 2024: The nostalgic desire to experience the mid-twentieth-century aesthetic provided by the glow and design language of Nixie tubes has still not gone away. But this niche demand has not been nearly great enough to keep them in production. And now, the last backstock versions of true Nixie tubes, produced in the Soviet Union and Eastern Europe in the 1980s, are at the end of their lifespans. At this point, anyone seeking that old-school glow can find it only in lookalikes made from more contemporary display technologies, like OLEDs that run on much lower voltages and whose manufacturing processes are much less labor intensive. //
Original article from 25 June 2018 follows:
On a cold December morning in the Czech village of Březolupy, a man stops his truck in front of a 17th-century castle. He puts on some heavy gloves, steps out of the truck, and opens the back hatch. Carefully, almost lovingly, he unloads crate after crate of heavy equipment and supplies—an industrial glass lathe, a turbomolecular vacuum pump, and glass. Lots and lots of glass.
The man is Dalibor Farny. In 2012, Farny began working to revive the manufacture of a display technology called the Nixie tube, the last commercial examples of which were produced when he was still a child.
These neon-filled glow lamps were ubiquitous in the late 1950s and 1960s, illuminating numbers, letters, and symbols in scientific and industrial instrumentation. Born in the basement of a German-American tinkerer in the 1930s and later commercialized by the business equipment maker Burroughs Corp., Nixies displayed data vital to NASA’s landing on the moon, lit up critical metrics for controlling nuclear power plants, and indicated the rise and fall of share prices on Wall Street stock exchanges, among thousands of uses. For many people, the warm glow of the Nixie came to evoke an era of unprecedented scientific and engineering achievement, of exciting and tangible discoveries, and of seemingly limitless progress. Remarkably, it continues to do so, even for people who, like Farny, grew up long after the tubes had faded from common use.
The picture shows my home-built digital clock, using Nixie tubes for readout. In contrast to most other nixie clocks being built these days, this clock does not use any transistor or IC for controlling and driving the tubes. Instead, the driving logic is built from trigger tubes, together with resistors, capacitors and silicon diodes. A video is on youtube.
This project is a followup to a similar clock I built between 2002 and 2007, documented on its own page. That clock used regular NE-2 style neon lamps as logic elements. Unfortunately, after a while, as these lamps aged, the clock became unreliable and unusable.
The new clock uses trigger tubes, of the МТХ-90 type (that's in Cyrillic characters; transliterated to Latin script it's MTH-90), which are widely available as "new old stock" on Ebay. Trigger tubes are essentially regular neon lamps with an extra "trigger" electrode, which can be used to ignite them. However, in this circuit I don't use the trigger electrode.
The above shows my home-built digital clock. It uses Nixie-tubes for readout. In contrast to most other nixie-clocks being built these days, my clock does not use any transistor or IC for driving the tubes. Instead, the driving logic is built from neon lamps, together with resistors, capacitors and silicon diodes.
The project started in 2002, when our university library was selling old outdated or otherwise superfluous books, and I very cheaply bought the book "Electronic Counting Circuits" by J.B. Dance, published in 1967, and apparently only ever lent three times by our library, all in 1973. It described how neon lamps can be used as logic elements in a ring counter, exploiting the fact that they need a higher voltage to ignite (the striking voltage) than to stay lit (the maintaining voltage):
Cross reference between NEMA and IEC schematic diagram symbols
The era of mainframe computers and directly programming machines with switches is long past, but plenty of us look back on that era with a certain nostalgia. Getting that close to the hardware and knowing precisely what’s going on is becoming a little bit of a lost art. That’s why [Phil] took it upon himself to build this homage to the mainframe computer of the 70s, which all but disappeared when PCs and microcontrollers took over the scene decades ago.
The machine, known as PlasMa, is not a recreation of any specific computer but instead looks to recreate the feel of computers of this era in a more manageable size.
Wednesday 19th June 2013 20:24 GMT
bscottm
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Re: It just costs money
It's not the GHz clock cycle that is the problem. It's the smaller feature size of the transistors that increases the single event upset (SEU) rate. Yes, the two are inter-related, but one could conceivably build multi-core, chip symmetric multiprocessors based on the PDP-11 at today's feature sizes and not have GHz clock cycle times (and still end up with significant SEU rates.)
A couple of years ago, a NASA/JPL scientist pointed out that the alpha particles (helium nuclei) from lead solder were causing interesting issues with current x86_64 I/O pins -- radiation issues on commodity hardware.
Convert an old computer ATX power supply into a highly capable workbench power supply. A perfect project for the budding experimenter with no spare cash for test equipment.