Nanduino » Construction
Step 1: Tool-Check
Constructing the Nanduino is non-trivial and requires a good-quality soldering iron. I use a Weller WD1000 which you can get from Rapid and Farnell amongst others, with an SMD tip.
Step 2: Order the Components
The microcontroller is an Atmel AT90USB162, which you can get from Farnell for the price of a pint; similarly you should get the USB connector from Farnell. The other components are best ordered from Rapid:
| Rapid Order Code | Description | Quantity |
|---|---|---|
| 90-0370 | 16MHz Crystal | 1 |
| 71-4225 | Pack of 10 EUCT3216 1uF Tantalum Capacitors | 1 |
| 71-4280 | Pack of 10 EUCT3528 10uF Tantalum Capacitors | 1 |
| 71-2026 | Pack of 100 0805 220nF Ceramic Capacitors | 1 |
| 71-1310 | Pack of 100 0805 22pF Ceramic Capacitors | 1 |
| 22-1751 | 0.1" 32W Turned-Pin SIL Socket Strip | 1 |
The capacitors listed above come in orders of 100 for the ceramics and 10 for the tants...it probably makes sense to order that kind of quantity - they are very useful components to have around.
Step 3: Solder the Components
Start with the microcontroller. Apply plenty of flux, then align the micro on its pads, with the pin 1 indicator pointing to the USB socket on the board. Solder two opposite corners of the chip to keep it in alignment, then solder the other pins by dragging a blob of solder down each side using a good surface-mount soldering iron tip. This technique makes use of the surface-tension in the solder to avoid bridges, but if a bridge should occur you can usually fix it pretty easily by removing excess solder with a solder-sucker. Don't use desoldering braid because it can quite easily tear up the delicate legs of the micro.
Next, solder the capacitors. Make sure you keep the correct polarity for the tants. The (+)ve marker on these is a little line; both tants have their (+)ve terminals pointing towards the top of the board. Soldering these is much easier if you have someone to help you...they hold the cap in place using tweezers and you solder it in place.
Next, if you have a home-made board (i.e, no plated-through holes) solder small pieces of single-core wire into the seven vias making a soldered connection on the top and bottom layers.
Next solder the USB connector. This should be aligned with its pads and the four case legs soldered in place before you tackle the pins themselves. This can be tricky to get right so use plenty of flux, and use a similar drag method that you used with the micro. Remove bridges with a solder-sucker.
You now have a choice. Except for the ground pin on the jumper block (which needs a connection to both sides of the board), all the through-hole components need an electrical connection only to the top of the board. You will therefore find it much easier to solder the through-hole components to the bottom of the board, so you can solder their legs on the top side of the board. If you don't do that, you will have to solder the components to the top-side of the board, which is possible, but quite difficult.
Step 4: Check your soldering with a multimeter
It's a good idea at this stage to check your soldering with a multimeter, to make sure there are no unexpected shorts or dry joints.
