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Jon Clift's Blog

60 posts
Last week I did a blog where I looked at the response of an LED to light: Experimenting With Using an LED as a Light Sensor . I thought it might be interesting to extend that a little bit further.   As before, the input is a reverse-biased LED acting as a photodetector. Again, I'm going to use an op amp as a transresistance amplifier (this time a Microchip device that can operate on 5V) but, for a bit of added interest, instead of generating an output voltage that's linear with diode cur ...
Does an LED work as a light sensor? Short answer is yes. That's fairly well known, but I've never tried it myself, so here goes.   I'm going to use a couple of old high-brightness red LEDs. I don't know much about them other than that they are definitely high in brightness, have a narrow viewing angle, and the package is 'crystal clear'.   My light source is an Arduino flashing one of the LEDs five hundred times a second [if jancumps can do a 'blinky', so can I!]. I've got a 330R res ...
Introduction   In a recent thread here, I mentioned to dubbie that it might be possible to use the balanced modulator in an RF mixer chip to create a Dalek sound effect. Later on, I discovered that I had a couple of them [in the old DIL package, too], so I though I'd do a quick bit of hardware hacking and see how they manage at audio frequencies. The mixer is based on a Gilbert cell, which will, of itself, work right down to dc, but there is internal biasing of the transistors, which t ...
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Bauble

Posted by jc2048 Dec 27, 2019
Recently, element14 was kind enough to send me a 'swag pack' which included a solderless breadboard. I wondered what to do with it as a quick blog and then remembered a small and very simple experiment I had thought of some time back and never tried.   My starting point was this episode of The Learning Circuit 32:  Making a FET Phase Light where Karen gave us a circuit to sequence three LEDs. Perhaps I could extend it and make it a ring of nine sections. Would that work? We'll see ...
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Swag Pack November 2019

Posted by jc2048 Nov 26, 2019
Received this 'swag pack' last week.       Not sure why I got it, but thanks anyway. I like the Faraday and Lovelace stickers, they're cool. I'll see if I can do something with the Uno. ...
Introduction   NIC stands for Negative Impedance Converter. It's one particular circuit configuration that can exhibit the phenomena of negative resistance. I'm going to look at that first and then, once we've done that, I'm going to use a pair of them to power a rather curious oscillator circuit due to Chua (the fun bit).   An Op Amp Negative Impedance Converter   As I'm sure you all know, a simple passive resistor has a property called resistance. The resistance is the con ...
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Chaos

Posted by jc2048 Apr 30, 2019
I've just been playing with Chua's circuit, using a couple of op amps for the negative resistance element. It makes for some pretty XY plots on the oscilloscope. Thought you might like to see them.       It's very finicky getting the values right and you can see from the bottom trace that it's not very stable, but it's good fun to play with.   Here's a link to the follow-up blog where I go into more details about the circuit I was using: Op Amps: NIC (Negative Impedanc ...
This is another exploratory blog relating to bipolar junction transistors (BJTs). It follows on from a previous blog which can be found here Transistors: Saturation   Be aware that I'm not an expert in all this: I'm studying it and you're looking over my shoulder as I experiment and explore the subject. So this is not a tutorial and it's possible that some of my explanations may, at times, be wrong.    Introduction    In the previous blog I looked at the collector and base s ...
A Transistor Load A Transistor Load: Stability A Transistor Load: Stability Part 2   Introduction   Important note: I'm learning about design with transistors and this is an investigation of transistor design techniques and presents a first prototype of a possible circuit, it's a long way from being a finished project suitable for replication.   I said in the original blog that I'd explain how I arrived at the design, so in this blog I'm going to give a quick run- throu ...
Introduction   This is a short follow-up to A Transistor Load which I blogged about as part of the Project14 Test and Instrumentation competition.   In the last blog A Transistor Load: Stability I got as far as compensating the amplifier section with a single 'dominant pole' capacitor and looking at the way the dynamic response was affected by different capacitor values. I also looked at the issue of lead inductance in the output current loop. I've done a little bit more work on ...
Introduction   This is a follow-up to A Transistor Load which I blogged about as part of the Project14 Test and Instrumentation competition. Since then I've been looking at the way the load performs, so this blog is on the subject of stability. By 'stability', I mean not only whether there's the possibility of the circuit breaking into sustained oscillations, but whether we might be close to that and the waveforms might ring badly (damped oscillations). To do this, I'm going to use th ...
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jc2048 Blog Index

Posted by jc2048 Oct 24, 2018
Electronic Art   9 Pieces of Pi: Slice 1: The Long Way Round 9 Pieces of Pi: Slice 2: Manifesto for Art Electronic 9 Pieces of Pi: Slice 3: Trickle Down to the Brave New World (This Way!) 9 Pieces of Pi: Slice 4: Fast Forward   micro:bit   The micro:bit Quartet PWM [micro:bit] Light Seeking Light Doth Light of Light Beguile [micro:bit] IO, IO, it's off to work we go! [micro:bit].   Arduino   Cool LED Displays: Boost That LED! UNO, Blue Man and the Neon Light ...
This blog is about a ladder. Another one.   A few days after I had finished the series of blogs I did on the R-2R resistor ladder I was in my local library, browsing the shelves in the way that you do, when I came across a book [1] on the history of the early days of analogue electronic music synthesizers - it was specifically about the Moog Synthesizer Co, though with lots of references to his main competitors: Bucchla, EMS, Oberheim and so on. It was an interesting read, though it focuse ...
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Op Amps - The Norton CDA

Posted by jc2048 Aug 30, 2018
Introduction   This blog is a bit off the beaten track and features an unusual form of op amp called a Norton amplifier. Perhaps I should have called it 'Op Amp Inessentials'! If it's not your kind of thing, skip it and go on to something more interesting.   The devices have been around for a long time but I've never had any cause to use one in a design. People are obviously still using them, though, as TI (who now own National Semiconductor) still list and sell the device I'm go ...
Introduction   Even more oscillators!   At some point, for reasons I can't remember now, I tried simulating some simple sine wave oscillators. At the time they all got left in the simulator's default save directory which is where I've been retrieving them from.   The last blog looked at a very simple and, to be honest, not very good single-transistor design Transistors: Phase-Shift Sine Wave Oscillator   This one, in contrast, uses op-amps to provide the gain and p ...