Small steps are never as easy as you imagine.

The first stripboard prototype has now been put together and it was worth doing. It works, but has taught me a lot about how the proof of concept design is likely to go together.

Prototype, mk 2: "Ever closer to approximate perfection"

The strip board module, with the AtMega chip, clock, leds, buzzer,
voltage regulators and many many pinouts.

First observation from putting it together was that it took most of a day, and was incredibly fiddly. The build time may come down with repetition and the fiddlyness could be remedied with an extra bit of clever design, but for something I want to be straightforward to put together, it is not acceptable. Therefore I may have to make a diversion to PCB land, which will delay the full completion of the proof of concept system (as as adding cost) but will make the design much easier to build.

A good test for new hardware is to use it. Typically this test is used when you have not put in good testing points, test procedures, or you are bored and want excitement. Also typically new hardware will fail this test and you have to spend twice as long fixing it. Test procedures for the strip board layout included (in order, and initially with no power or DIP chips):

1. Testing for Power-Ground shorts (good for not blowing up components when you plug it in).
2. Test for signal-ground shorts (same).
3. Test for Micro-controller to endpoint signal wire/trace continuity.
4. Test to see if the voltage rails had the right voltage (with battery plugged in).

Then the following functionality tests were performed (once the DIP chips had been socketed, and the micro-controller programmed):

1. [PRIOR to all other tests, the AtMega chip was used in the breadboard setup to read cards and demonstrate basic functionality, proving it worked)]
2. Test to see if the clock worked (and the buzzer), performed by waiting a minute to see if the 'I-updated-from-the-RTC' blip activated.
3. Test to see if the serial interface (through the now empty UNO board) still worked.
4. Test to see if the RFID reader worked.

Absurdly the tests were all passed until the last one. The brilliance of not doing the 'plug and go' test was that I knew the RFID reader/wiring to the RFID reader was at fault. Plugging the RFID reader back into the breadboard setup showed it was still working, which meant the problem was in the wiring. Quick testing indicated one of the pins was shorted to ground, which it was due to some splashed solder. Fixing this meant the device worked normally, but such a fault indicates that even when you know the design well, test thoroughly and have plenty of soldering experience with these sorts of components it is still tricky to get a working board. If others are to be able to replicate the design it has to have a fair chance of working first time with no debugging, something this approach is evidently unlikely to achieve.

I lie when I say all tests were passed, the 5V regulator was actually counterproductive with the 5V supply - I had expected it to operate without any voltage drop but it appeared to just not work! Therefore it was just shorted out, and will be in any future designs that use the magic Poundland power supplies.

The placement of components is also an issue. Due to the nature of the Strip board, placement of components (when optimising for reduced soldering) is not exactly free, and as a result (as you may have spotted in the photo of the board), the board is not set out particularly well. The LEDS are recessed, which is not ideal if they are to be visible. The Header pins are spread out all over the board, not ideal for happy wiring in the final enclosure. (Though to be fair I have not thought much about how the final enclosure will look yet). Moving these bits around requires more flexibility in routing than the strip board can give me, which does not bode well for it!

To sum up, stripboard: meh, PCB: possibly worth the extra expense...

Next step will be to think about the enclosure, then go off and order the enclosures, RFID units and PCBs. Then take a trip to documentation land while I wait for them to arrive!