Dual Seven Segment display madness

Preamble

One day, in March 2015, whilst shopping for Arduino bits and pieces in Ban Mo, an electronics street market in BKK, I came across a large sheet of polystyrene bejewelled in Sanyo SL-1255-30 two digit seven segment displays, for 5 Baht each, which was displayed in the street outside a shop. I purchased one of the seven segment displays, took it home, and eventually realised that no libraries existed for the common anode device. So I promptly set about writing my own sketch, which then evolved into an Arduino Library that was developed over the course of a couple of weeks. This is that library.

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LED Walls, Cubes and Curtains

Preamble

A good friend of mine from the Riddim Shack, Koh Chang was after an eye-catching display for his mobile tuk-tuk bar now based in Sihanoukville, Cambodia. He wanted it to stand out from the crowd and be noticeable from a distance. I immediately proposed an LED wall, or curtain, that could be controlled by an Arduino based controller. This would open up a range of possibilities, rather than just a static display of lights. For example, in-bar advertising, an LED spectrum analyser display in beat with the music, videos, images, not to mention just random visual effects. The resolution does not have to be excessive, as it is surprising how forgiving the eye is on moving images, the ear is a much more strict master. Glitches in audio tracks make one wince, but video corruption is not a biggy. In fact, this is why in the olden days, when System 7 was cutting edge, Apple’s QuickTime gave priority to the audio track, and let drop outs occur on the video, if processing power was momentarily outstripped.

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Raspberry Pi, Motorola Atrix Lapdock and Arduino Hoody

Preamble

I bought a Raspberry Pi in Thailand at the start of the year. I got it working with a Motorola Atrix Lapdock (Lapdock for Motorola ATRIX 4G 11.6″ Motorola AT&T) that I purchased new on eBay for about £70, from Israel.

Motorola Atrix Lapdock
Motorola Atrix Lapdock

It has a Hebrew keyboard and the brackets glyphs are on the incorrect keys, but apart from that it is fine.

I then built an Arduino Hoody (which is equivalent to an Arduino shield), as described in the Instructables guide: The Raspberry Pi – Arduino Connection by , which uses an Arduino Mini Pro 3.3V.

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My Arduino Babies

Preamble

How did I get into Arduino? That is a good question, and one whose answer will entail the discovery of Stack Exchange, Super User, just before Xmas 2014. I think I was just looking for an answer to a Wi-Fi issue that I was having with a Mac. That then led on to me exploring the SE network, and finding SE Raspberry Pi, with with I was already familiar, having heard about it in the British press (i.e. BBC News). Then there was a question asking something along the lines of “What should I get – an Arduino or a Pi?” I had never heard of Arduino and so did a bit of googling, at bit of researching, and then a lot more googling and researching, and realised that this was something that I wanted to get into.

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XBee expensive expenses

Preamble

I got hold of the excellent ebook, Building Wireless Sensor Networks – A Practical Guide to the ZigBee Mesh Networking Protocol, by Robert Faludi, published by O’Reilly. download it here or here. (Useful links: errata and; code).

Building Wireless Sensor Networks Cover
Building Wireless Sensor Networks Cover

I read a good part of it on Valentine’s day 2015 in Viva8, a kicking bar in Chatuchak market (the [in]famous big one in BKK, where you can buy snakes, dog meat, dinosaurs and old sets of false teeth).

I was hooked, they looked great, and the book was full of interesting projects. I soon figured out what was what, and what was required, or rather what I required.

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Choosing which multimeter to buy

Preamble

I was living in Bangkok, and had resurrected my past interest in electronics, most notably through using Arduinos.  After playing about for a few weeks I realised that I sorely needed a digital multimeter (DMM). I already own one, from my days at university, 27 years ago, a M-776 Precision Gold Autorange Digital Multimeter (with transistor tester and display hold) from Maplin. Cost me £20 at the time, which seemed like a lot of money back then (for a pound you could do the week’s shopping, have a night out on the town, entertain some ladies and still have enough money to get the bus home – not any more, eh?), although I seem to remember it being a top of the mid-range model, so it was worth it.

Maplin Precision GOLD M-776 DMM
Maplin Precision GOLD M-776 DMM

I have still got the box it came in!

The Box that the Maplin M-776 DMM came in
The Box that the Maplin M-776 DMM came in

Anyway, I digress… so the M-776 was no good to me back in the UK, when I’m in BKK, so I thought that I might as well splash out and get a new one, for two reasons:

  • It is always handy to have two, so that you can simultaneously measure current and voltage, and;
  • The newer models were bound to have better features than the M-776

Now, which one to buy?

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My first oscilloscope

Preamble

I’ve been looking at http://www.bitscope.com/pi/blog/ for some time now, it was one of the reasons that goaded me into buying a Pi 2 in the first place. It’s a scope, logic analyser and signal generator in one. Not something I’ve determined I even need, so for now I’m holding off, plus a little on the pricey side, £100, and of limited bandwidth (10 MHz).
Ah ha! That is the blasted link that caused all this in the first place. However, it is no good for me, a pathetically narrow bandwidth. As I’ve said, it’s about 10 MHz. I was using 20 MHz ‘scopes in Tech College and University, 30 odd years ago, and at the time I had always hankered after a 50 MHz oscilloscope. So 100 MHz would be exceeding previous aspirations. Ah well, I’ll probably never use it anyway. In Thailand, I bought a 100 quid multimeter that does everything, a UNI-T UT-71D, even heats up Baked Beans for you… yet I’ve only ever done continuity tests with it! A total waste of money, when a $10 DMM would have sufficed.
So anyway, I ended up buying a rudy oscilloscope on eBay this morning, half asleep, for 60 quid!!! I didn’t want it really, but had to go to Wokingham to pick it up. However, I also ended up seeing an old friend, who I hadn’t seen for a long while, so not a totally wasted trip.
“What do I need a silly scope for?”, I hear you say… well, I’ve got heavily into Arduinos. To date, I have 3 x Nanos, 2 x Unos, a Mega, a 3v3 Mini pro and a 3v3 Micro pro (these two all linked to the Pi and Motorola Lapdock), and a Leonardo. I’ve done some stuff, written a library for a dual seven segment display and a graphic equaliser display. Totally pointless waste of two months obsession. Now I am building a spectrum analyser. I found a great oscilloscope actually this morning, but only good for up to 300Hz. I got into the Arduinos via Stack Exchange (SE). Basically, by Xmas I was so bored of Thailand and the girlfriend and drinking excessively that I decided to do something productive and educational, instead of picking fights with the local Yakuza. So, I started answering questions on SE Super User. Then I saw SE Raspberry Pi so joined that, then heard about Arduino, looked into it, opened eBay and went wild. I literally had five packages a day for two months arriving cheap from China. So, now I have a suitcase full of multimeters, Arduinos, shields and modules but no clothes.

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