Do you still have an old analog CRT television lying around? With the advent of digital signals, analog TV´s are going to the dumpster or the recycling center. But you can still put them to good use, just as [GreatScott!] did, by converting the TV into a crude oscilloscope.
The trick is to take control of the two deflection coils that move the electron beam inside the CRT in the horizontal and vertical directions. The video describes in detail the process of identifying the coils and using an Arduino nano in combination with a DAC to amplify the input signal in order to get the waveform in the TV screen. Step by step explanations and great editing make this project delightful to watch.
Even if you do not follow [GreatScott!]´s steps to build a simple oscilloscope, don´t throw away that vintage TV!, it is a great source of analog parts. The flyback transformer can be used to make a high voltage power supply, and you also get some nice high voltage capacitors (both electrolytic and mylar ones), the horizontal output transistor which is a high voltage one, ferrite transformers, magnet wire, plus a lot of other small parts. Other uses for old TV sets that you may want to try is to convert your TV into a gaming console, or an audio synthesizer controlled by drawing with a light-sensitive pen on a CRT television.
Continue reading “Hacking a Vintage TV into an Oscilloscope”
Pong may not be much anymore, but it’s the granddaddy of all video games, and there’s still a lot to learn by studying its guts. And what better way to do that than by having it all laid out before you as you play? All it takes is 200 discrete transistors and two large handfuls of passives tacked to a piece of copper clad board to get a version of Pong executed without a single chip that’s playable on an oscilloscope.
Clearly a labor of love, if not an act of temporary insanity, [GK]’s realization of Pong is a sight to behold. Every scrap of it is circuits of his own design, executed dead bug style, apparently because [GK] enjoys life on hard mode. The game itself is surprisingly playable and you can even play against the machine. The video below is a little hard to watch, what with some glare on the oscilloscope CRT, but we’ll cut [GK] plenty of slack on this one; after all, it looks like this whole project was pulled off in one marathon weekend build session.
We’re still busy poring over the hand-drawn Forrest Mims-style schematics, which by themselves are almost a complete course in analog design. A lot of the circuits remind us [GK]’s bouncing ball simulation, which we covered a while back.
Continue reading “Jaw-Dropping, IC-Free Pong on an Oscilloscope”
The latest CrowdSupply campaign is a wireless, Bluetooth oscilloscope that doesn’t make a whole lot of sense until you really think about it. Once you get it, the Aeroscope wireless oscilloscope is actually a pretty neat idea.
If the idea of battery-powered, Bluetooth-enabled test and measurement gear sounds familiar, you’re not dreaming. The Mooshimeter, also a project on CrowdSupply, is a multichannel multimeter with no buttons, no dial, and no display. You use the Mooshimeter through an app on your phone. This sounds like a dumb idea initially, but if you want to measure the current consumption of a drone, or under the hood of your car while you’re driving, it’s a really, really great idea.
The specs of the Aeroscope aren’t bad for the price. It is, of course, a one-channel scope with 20 MHz bandwidth and 100Msps. Connection to the device under test is through pokey bits or grabby bits that screw into an SMA connector, and connection to a display is over Bluetooth 4.0. You’re not getting a scope that costs as much as a car here, but you wouldn’t want to put that scope in the engine bay of your car, either.
The Aeroscope is currently on CrowdSupply for $200. Compared to the alternatives, that’s a bit more than the no-name, USB scopes. Then again, those are USB scopes, not a wireless, Bluetooth-enabled tool, and we can’t wait to see what kind of work this thing enables.
The oscilloscope is probably the most versatile piece of test equipment you can have on your electronics bench, offering a multitude of possibilities for measuring timing, frequency and voltage as well as subtleties in your circuits revealed by the shape of the waveforms they produce.
On the front of a modern ‘scope is a BNC socket, into which you can feed your signal to be investigated. If however you simply hook up a co-axial BNC lead between source and ‘scope, you’ll immediately notice some problems. Your waveforms will be distorted. In the simplest terms your square waves will no longer be square.
Why is this? Crucial to the operation of an oscilloscope is a very high input impedance, to minimise current draw on the circuit it is investigating. Thus the first thing that you will find behind that BNC socket is a 1 megohm resistor to ground, or at least if not a physical resistor then other circuitry that presents its equivalent. This high resistance does its job of presenting a high impedance to the outside world, but comes with a penalty. Because of its high value, the effects of even a small external capacitance can be enough to create a surprisingly effective low or high pass filter, which in turn can distort the waveform you expect on the screen.
The answer to this problem is to be found in your oscilloscope probe. It might seem that the probe is simply a plug with a bit of wire to a rigid point with an earth clip, but in reality it contains a simple yet clever mitigation of the capacitance problem.
Continue reading “How An Oscilloscope Probe Works, And Other Stories”
These magical creatures crop up out of nowhere and fry your electronics or annoy your ear holes. Understanding them will doubtless save you money and hassle. The ground loop in a nutshell is what happens when two separate devices (A and B) are connected to ground separately, and then also connected to each other through some kind of communication cable with a ground, creating a loop. This provides two separate paths to ground (B can go through its own connection to ground or it can go through the ground of the cable to A and then to A’s ground), and means that current may start flowing in unanticipated ways. This is particularly noticeable in analog AV setups, where the result is audio hum or visible bars in a picture, but is also sometimes the cause of unexplained equipment failures. Continue reading “WTF are Ground Loops?”
Metropolis is a classic, silent film produced in 1927 and was one of the very first full length feature films of the science fiction genre, and very influential. (C-3PO was inspired by Maria, the “Machine human” in Metropolis.) Within the first couple of minutes in the film, we get to see two clocks — one with a 24-hour dial and another larger one with a 10-hour dial. The human overlords of Metropolis lived a utopian 24 hour day, while the worker scum who were forced to live and work underground, were subjected to work in two ten-hour shifts during the same period.
[Aaron]’s client was setting up a Metropolis themed man-cave and commissioned him to build a Metropolis Oscilloclock which would not only show the 24 hour and 10 hour clocks from the film, but also accurately reproduce the clock movements and its fonts. [Aaron]’s Oscilloclock is his latest project in the series of bespoke CRT clocks which he has been building since he was a teen.
The clock is built around a Toshiba ST-1248D vintage oscilloscope that has been beautifully restored. There are some modern additions – such as LED glow indicators for the various valves and an external X-Y input to allow rendering Lissajous figures on the CRT. He’s also added some animations derived from the original poster of the film. Doing a project of this magnitude is not trivial and its taken him almost eight months to bring it from concept to reality. We recommend looking through some of his other blog posts too, where he describes how oscilloclocks work, how he builds the HV power supplies needed to drive the CRT’s, and how he ensures vibration and noise damping for the cooling fans used for the HV power supplies. It’s this attention to detail which results in such well-built clocks. Check out some of [Aaron]’s other awesome Oscilloclock builds that we have featured over the years.
The film itself has undergone several restoration attempts, with most of it being recovered from prints which were discovered in old archives. If you wish to go down that rabbit hole, check out Wikipedia for more details and then head over to YouTube where several versions appear to be hosted.
Continue reading “Decimal Oscilloclock harks back to 1927 movie”
After getting a power supply and a multimeter, the next piece of gear a hacker would want to add to their bench is the oscilloscope. Nowadays, even the cheapest ones cost a few hundred dollars yet pack in the features. At the other end of the scale, if you can pony up close to a million dollars, you can help yourself to an oscilloscope capable of 100 GHz bandwidth and 240 GS/s sampling rate. With that perspective, it becomes interesting to take a look at this video (embedded below), where [Jack Ganssle] shows us the Philco 7019 Junior Scope which was introduced way back in 1946. It seems the Philco 7019 model was an identical re-badged version of the Waterman Model S-10-A PocketScope.
[Jack] is familiar to all of us as an embedded systems engineer, but in this video he does a teardown of this vintage analog model. He starts off by walking us through the various controls, of which there are not a lot, in this “portable” instrument. At around the 3:40 mark in the video, he’ll make you wince as he uses a screwdriver and hammer combo to smash another ’40’s vintage CRT just so he can show us it’s innards — the electron beam source and the horizontal and vertical deflection plates. The circuit is about as bare-bones as it can get. Besides the CRT, there are just three vacuum tubes. One is the rectifier for the power supply, a second one is used for the vertical amplifier while the third one is the free running horizontal sweep oscillator. There is no triggering option — you just adjust the sweep frequency via a potentiometer as best you can. It does have internal, external and line frequency function selection, but it still requires manual adjustment of the sweep oscillator. There’s no blanking signal either, so the return sweep is always clearly visible. This is evident from the horizontal burn mark on the phosphor of the CRT after decades of use. It’s amusing to see that the vertical position could be adjusted by moving a magnet attached to the side cover.
The Oscilloscope Museum website hosts the Instruction Manual for this model, as well as a sales brochure which makes for very interesting reading after viewing [Jack]’s video.
Thanks, [Itay], for the tip.
Continue reading “Taking Apart a Vintage Oscilloscope”