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Jon Clift's Blog

31 posts
Part one is here: https://www.element14.com/community/people/jc2048/blog/2018/04/12/arduino-r-2r-experiment   I was going to do some hardware next but got sidetracked into playing with software instead.   Here's a very well-known waveform being produced by the simple resistor-ladder DAC I built in part one.       and here's what it looked like before I got the arithmetic right       That's generated by this sketch   // //  --- Sine table ...
jc2048

Arduino: R-2R Experiment

Posted by jc2048 Apr 12, 2018
R-2R sounds like it might be a robot from the Star Wars universe (a ladder robot, maybe?), but in electronics it's the name of a resistor network that can be used to make a DAC (digital-to-analogue converter). I'm going to try doing just that with an Arduino and see how I get on. If this works, it's then going to be the basis for a piece of Arduino test equipment controlled by the SCPI library that Jan introduced us to last weekend.   The network looks like this. This is from the simul ...
I'm still very short of time, so this blog is just a quick, simple one.   Well, it had to happen eventually, here I am doing the astable multivibrator (an oscillator circuit).   This is going to be in two parts. First a look at the circuit in the simulator and then I'm going to build one. That second part will be a trip down memory lane for me because this is the first circuit I ever built and I'm going to have a go at recreating, in a modern form, what I did back then. More on tha ...
Back when I first became interested in electronics, a simple way to make an oscillator was a circuit called an astable multivibrator. These got used a lot - the electronics magazines that I used to buy as a teenager were full of them. This is the form of it     The two transistors are arranged like a flip-flop, with either one or the other conducting. Unlike the flip-flop, where the conducting transistor will hold the other off, here the additional capacitors mean that after a pe ...
It seems 2018 is going to be the 'Year of the FPGA' here on element14 ('Forward Heroic Engineers of the World to a Flip-Flop Rich Future'), so I thought I'd join in, buy a small development board and do a simple project or two. The board I'm working with here is the Brevia2 board from Lattice[2].   Part 1 covered unpacking the board, connecting it to the computer and checking that it worked:   Booards and Boojums: Lattice XP2 Brevia2 Board: Part 1   In this part I'm going to tr ...
It seems that 2018 is going to be the 'Year of the FPGA' here on element14, so I thought I'd join in, buy a small development board and do a simple project or two.   Here's the board I settled on in the end. Rather than go for Xilinx, which I've worked with in the past, I decided to experiment with a Lattice FPGA and their toolset. I liked the look of this board because it's quite simple, with just an XP2 series FPGA part (in the kind of package where you can see all the pins) along wi ...
Cool LED Display Monthly project competitions, chances to earn prizes, you decide project themes, your ideas, your projects, turn ideas into projects. Back to The Project14 homepage Project14 Home Monthly Themes Monthly Theme Poll   Cool LED displays. I don't have a lot of time at the moment, but wanted to do something [I did vote for it, after all] so I've thrown together this - a simple bit of experimenting with an Arduino.   Rather than just light an LED, I thought I'd make i ...
I really should be doing other things, but I can't resist doing another quick piece of DIY Test Equipment. Again I'm going to post it here in my blog. I haven't worked it up into a polished piece of equipment - it isn't even really finished - instead I'm piecing together a design that you could take 'as is' and finish nicely or use the building blocks for something quite different.   This time it's a diode tester. Operation is quite simple: I'm going to pass a current through the diode ...
I hadn't even realised that we were on to Doug's DIY Test Equipment Challenge and, look, shabaz has finished already with his Cyclops-1000: An Electronic Eye for Rotational Speed Measurement. I bet he's sitting there thinking he's won. We can't let that go unchallenged, so here's my first try. I don't expect it will win; not just because I'm posting it in the wrong place and technically I can't win, but also because I've just thrown it together without all the careful thought and consideration t ...
Back in February, I visited one of the small museums that exist in the town where I live. It's a natural history museum and is based in an old church. It's a lovely place to visit, with lots of curious things to look at. In the shop, on the way out, there was a basket with small chunks of rocks and minerals for sale and I bought a small piece of 'fool's gold' (iron pyrites); I figured that an old fool like me deserved a piece of gold to treasure.     What I didn't know back the ...
The other day, I was sorting through some old boxes and found a small bag of old transistors. There were two types, both of them PNP devices. One kind was an OC204 part, made by the old British company Mullard, the other a 2S3220 device made by Texas Instruments. I presume they date from the 1960s.         I wondered if they still worked and what their characteristics would be like compared to a modern device so I built up this circuit of a simple common-emitter amp ...
jc2048

Solar Garden Light

Posted by jc2048 Mar 31, 2017
A couple of days ago, I was in a store here in the UK (in the garden department looking at seeds and bulbs) when some 'solar lights' caught my eye. The very cheap ones didn't look up to much, but the £2 ones had a decent solar cell on them so I bought one. I was curious as to how something with a CE sticker saying it had a 1.2V battery inside was able to light a white LED that would need a forward voltage of around 3V to illuminate.   Here are some photographs as I disassembled it. ...
This one is similar to what I did with the gain, except that this time I kept the base current constant and measured the collector current in relation to the collector-emitter voltage. I reworked the original test circuit, which is how this blog follows the last one so quickly. As before, I'm looking at an NPN bipolar junction transistor (a 2N3904) and the situation where the emitter is the common terminal between input and output.   Here's the circuit (minus decoupling caps):    ...
Another 'Transistors' blog. I thought this one would be easy, but it turned out to be quite challenging and, in some ways, a bit of a failure.   The current gain of a bipolar junction transistor (when the emitter is the common terminal between input and output) is the ratio of collector current to base current. In some ways, it's the most fundamental parameter that the transistor has, because our simplest conceptual model of the device is something that takes an input current and p ...
Part 1 can be found here:   PID on a EK-TMC4C123GXL Evaluation Board. Part 1: Getting started.   At this point I had to decide what to try and control. I wanted something that would be slow enough that the processor could keep up, but fast enough that it would present at least some kind of a challenge. In the end I decided to do that most traditional of things, the one that everyone does with a new processor board, I'd light an LED. Here's the LED     it's a 1W warm whi ...