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Jon Clift's Blog

26 posts
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 ...
When jancumps introduced us to the PID library (link below) I said I'd have a go with it, since I had a TI evaluation board (an EK-TMC4C123GXL with a Tiva TM4C123G on it), wanted to learn a bit about ARM coding, and thought that running a control system with a processor in the loop sounded interesting and a bit of a challenge, but it's taken me a while to get started, what with the transistor blogging and everything.   MSP432 and TI-RTOS: PID Library Part 1 - Intro   First aim is ...
I thought I was going to do saturation next, but somehow I've diverted off into looking at the transistor as a diode. This came about from my referring to Bob Pease's book, Troubleshooting Analog Circuits, to look up something else and then thinking that I'd like to measure for myself the graph he shows of Vf against If for various diodes, including transistors connected as diodes.   A bipolar junction transistor contains two PN junctions, one between the base and the emitter (B-E) and o ...
A further blog in my series about transistors [I think I've given myself a lifetime job, mining this rich seam]. This one looks at the reverse breakdown of the base-emitter junction and one application of the transistor if it's used in this way [actually, I only know of one application, but no doubt D_Hersey will be along in a while to quote half a dozen from the Electropedia that sits inside his head].   On a datasheet the maximum figure for this junction is often given as 5V or 6V (fo ...
This blog is a continuation of   Transistors: Vce Breakdown   and it's probably best to read that one first. The idea for this one came out of helpful observations made by mcb1, dougw, and D_Hersey in the comments, so read those too.   I'm going to look in a bit more detail at protecting a bipolar junction transistor switching a relay. In that previous blog, I was using a solenoid as the inductive load, now I'm going to use a real relay. It's a relay intended for automotive us ...
Another blog about transistors. This time, I fancied looking at a circuit rather than the characteristics of a device, so I'm going to look a circuit known as the Schmitt trigger. This is named after O. H. Schmitt, though his original circuit was published in 1938 and predated transistors. It's not necessarily a very useful circuit any more in this particular transistor form, but it is interesting to look at it and understand what is going on - partly just for its own sake, but also because I'm ...