The Shopping List

So, I settled down to an hour or two of eBay hunting, to cost out what I thought I would like to buy, and then decide if I could justify it using the 'number of coffees I will need to go without' equation.  Unfortunately, this turned into a couple of long evenings - I don't know if it's just me, but I have an awful lot of trouble with eBay - it seems sooooo slooooow to load up any page, and you try doing a search for Arduino Uno, and just see how many pages of results it throws up!!!

The next issue I had was that each listing often covers multiple product options, so there is no point sorting them by price to try and find the cheapest... When you open the listing that appears to be offering an Arduino Uno for just $1, you'll find that the $1 is just for the USB cable, or the header pins or some other optional extra - rather than for the board itself.  So sorting through all the 'false' adverts made this an incredibly slow and laborious task.  But hey, I'm a skinflint, so 2 hours of searching to save me 25c is well worth the effort.

I decided that I definitely wanted a breadboard, but I wanted one that's a reasonable size, not one that requires artful planning once you exceed 5 components...  I opted for a model called MB-102 which has 630 points in 126 blocks of 5, and then another 200 in + and - bus bars.  To go with this, I also decided that I needed connector wires in M-M/M-F/F-F formats, and a regulated power supply unit for the breadboard (well, it was only $1).  The power supply can run from a USB lead or from an external power source (such as the various mains adaptors I have salvaged from all number of devices over the years).  I also found a 9v battery lead with the same 2.1mm plug as the mains adaptors, which means I can also run the power supply from a 9v battery.

Then, I started drooling over the Arduino Uno listings, which inevitably brought up huge numbers of ads for add on sensors, shield boards, and all sorts of goodies, but first let me give you a few warnings about the ads for Chinese clone Arduino Uno 'compatible' boards.

1. They all seem to use a different USB controller chip (CH340) from the genuine Arduino (ATMEGA16U2).  This chip may need you to find and load the specific drivers for it, before you can plug in your Arduino (I will report back on that when mine eventually arrives).  It also means that they may have USB Mini or USB Micro sockets on them, rather than the Arduino's USB-B.  HOWEVER, I found lots of listings where the USB option described in the listing title did not match the pictures, or the pictures and detailed description were different (or even all three were different).  Sometimes a single listing even showed pictures that conflicted with each other.  Since the boards are frequently sold without a cable, it would be nice to know definitively what cable you need to buy without having to wait for the board to arrive.
2. Because the whole concept behind Arduino is that it is open-source, the clone boards may have additional 'enhancements', which can be very ambiguously described in the ads using very poorly translated Chinglish.  For example, in the listing that I eventually chose to purchase from, it mentioned an extra two rows of holes for the pins AND an extra three rows of holes for the wiring (clear?), and if you looked closely you could see that the pictures showed at least three different variants of the board from different manufacturers, that included varying configurations of extra pinout options (rows of holes) - so I am not really entirely sure what is going to turn up in the end...
3. Another 'enhancement' is that they mostly seem to use a slimline 'surface mounted' version of the main chip, which is soldered directly to the board.  If you mess up a circuit and fry the chip, you will have to buy a complete new board.  The genuine Arduino uses a replaceable chip that loads into a socket.  Mind you, when the entire Chinese clone board costs little more than the replaceable chip - I guess there is not much advantage lost.
4. Be careful to understand exactly what you are getting in any listing - make no assumptions.  I saw boards with or without cables; with header pins already installed, or with them separate, or with them as an 'extra'; with USB-B, Mini, or Micro sockets - or with ambiguous descriptions leaving you not really sure; with different pinout options (all over and above the 'standard' minimum, but still a bit frustrating).  If in any doubt contact the seller - but don't count on getting a clear or definitive answer from them either.  They often have a poor grasp of English, and are not necessarily even specialist electronics suppliers - they just buy and sell random 'stuff'.

Anyway - having said all that, I finally plumped on a particular listing, for a board with header pins (hopefully already installed), and three additional sets of pinouts designed for specific interfaces (again - hopefully), but without a USB cable.  According to the listing title, it has a USB Mini socket, but working in IT, I have access to dozens of spare USB cables of pretty much every configuration, so even if I don't have the correct cable for it at home, I am 99% sure I will be able to loan one from work until I can get what I need.

The final thing on my list is an LCD (text) unit.  The most commonly available option seemed to be 16 characters by 2 lines, but I opted for a 20 character x 4 line unit, that only cost an extra $1.50.  Something to watch for on these, is whether or not they have the IIC (I2C) backpack on them.  If they don't, then you will need at least about 8 or 9 data connections, plus power to hook them up, but with an I2C backpack, you can run them with just 2 data and 2 power connections.

So my final shopping list looks like this...

• Breadboard MB-102 - $2.59
• MB-102 Power Supply - $1.00
• M-M/M-F/F-F cables (40 each) - $4.42
• 9v Battery Leads (x2) - $1.00
• Clone Arduino Uno R3 (USB Mini) - $4.42
• LCD2004-I2C - $5.88
• TOTAL - $19.31 (or just under 5 coffees)

Update - 3 weeks later... only the breadboard and cables have turned up so far, but I've been using my time productively, as you'll see in my next post.