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There was one other component I almost forgot! The DS18B20 temperature sensor that goes on the PCB. I could have soldered that direct to the board, but put a pin header in instead and mounted the sensor in the plug:

The lid, complete with all wiring.

That’s almost all the soldering done. I think there are just the temperature sensor plugs and possibly a power cable to make up (I think I’ve run out) that will require more soldering work.

There are a few little gotchas here: the pinouts of the RGB LED at the bottom left, and the display connector at the top right don’t match the pinouts of the connectors on the PCB, so I’ve had to swap the ends around to get the order correct. The carrier board for the RGB LED was also quite awkwardly made in this instance — the LED was soldered very close to the board which didn’t leave me much room for manoeuvre when connecting the lead so it wouldn’t foul the side of the case. It uses a 90 degree pin header and I ended up bending it with pliers to make it more like 45 degrees. I assume that’s “natural variation” in manufacturing QA, as the first one wasn’t that awkward.

And of course, don’t do what “a friend of mine” did, and connect up all the GX12 sockets with their nice little caps to keep out dirt and moisture with the caps up the wrong way, then have to undo them all and put them on again the right way around. I, err, He felt such a fool when he realised.

Now I need to make up all the pin header sockets on the other ends of all those LED, heater and temperature sensor wires.

The remaining components in the case — the fan, USB connector, power socket and DHT22 are now fitted.

I drilled the mounting holes for the fan and USB socket through the walls of the case as I wasn’t confident that I would get a sufficiently neat hole if I’d 3d-printed them. For the DHT22 I used a 3-pin connector on one end with a 3-way cable and a 4-pin connector on the end that actually plugs into the sensor itself as it has four pins with no connection on pin 3.

I also found time to make a start on fitting components to the lid.

I did this on a night when I’d had to work very late. I went to bed and found I couldn’t sleep, so at half past three in the morning I got up and spent half an hour cutting wires to length for the rest of the components in the lid to try to relax 🙂

The next step was to finish off the diodes on their fly leads, covering the exposed leads with plenty of heatshrink.

I’m not at all convinced this is the best solution, but I’ve not come up with any better ideas where the prefab PCB is being used. Ideally I’d prefer to have the diodes fixed in position, much closer to the board.

I printed the lower section of the case, so it was time to fit the Nano to the PCB and put the PCB loosely in place so I could connect up the USB cable and see what happened. The good news is that it all lit up as it should and the LED that should flash did indeed do so.

I think it’s now time to start fitting all the bits and pieces that will go into the base (fan, USB socket, power socket, humidity sensor).

Temperature sensor plugs and sockets…

My dissatisfaction with the 6P4C connectors led me to try to find other options for plugging these in. Initially 3.5mm stereo jack plugs such as these sprang to mind.

However, Robert Brown himself explained to me that this idea had already been tried and had been found to have a couple of problems. First, the possibility of cross-connecting the inputs when inserting or removing a sensor connector with the power applied (which perhaps wouldn’t be a problem if this was always done with all power removed). Second, experience from people who have tried it shows that the currents involved apparently can lead to the plug and socket “welding” to each other because of the small contact area. This is clearly not desirable.

In the end I decided to try some 3-pin GX12 plugs and sockets (sometimes called “aviation connectors”):

In fact these don’t take up much more space than the original sockets and are much easier to fit and solder wires to.

I modified my design for the lid of the case and printed it out to try the sockets it. They seem to work well enough in terms of layout.