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Build It (FIGnition 2011)

These are the build instructions for the 2011 RevC and RevD edition boards. These boards have only one phono socket and look very similar to:


(RevC is on the left, RevD is on the right). A PDF of these instructions is attached, but here's the online version.

Building FIGnition:

The Kit

The kit should look like this and contains:

  • A small bag with a USB connector and other components.
  • Another small bag without a USB connector in it containing the rest of the components.
  • A plastic tube containing 3 sockets: 1x 28 pins + 2 x 8 pins.
  • An anti-static bag for your final FIGnition containing the PCB.
  • A plastic tube containing 3 chips: An AtMega168, a Microchip 23K640 8Kb SRAM and an AMIC A25L040-F 4Mbit Flash Chip (Batch 1 users get an 8Mbit chip for being risk-taking early adopters!). (You may find that the small 8-pin chips are in the anti-static bag).
  • A Receipt / Remittance notice thanking you for buying a FIGnition computer!

The first plastic bag contains the following components (it’s not antistatic):

Component
Quantity Identification  Colour Blind Identification
1K5 Resistor
6 Brown, Green, Black, Brown  For resistors, the best thing to do is use a
1K Resistor
6 Brown, Black, Black, Brown  multimeter and set the range to 2K. All the
220R Resistor
2 Red, Red, Black, Black.  resistors are +/-1%.
1N4148 Diode
4 Glass+Black stripe. Tiny writing that says: 1N,41,48  It should be possible to identify the black stripe.
LED
1 Red and Translucent (or transparent)  
10nF Capacitor
3 Round ceramic disc marked with "10" or "103"  
6x6mm Switches
8 Square with protruding buttons!  
Total
30
 

The second bag contains the remaining discrete components:

Component Quantity Identification
470R Resistor 1 Yellow, Purple, Black, Black.
68R Resistor 2 Blue, Silver, Black, Gold
22pF Capacitor 2 Round disc marked "22".
3v6 500mW Zener Diode 2 Glass+Black stripe. Tiny writing that says 3v6 somewhere
4.7µF Electrolytic Capacitor 1 Cylindrical with a white stripe.
20.0MHz Crystal 1 Metal oval-shaped can (top view) marked "20.000"
USB Connector 1 A Standard USB B-type connector.
A Phono Connector 1 Similar size to the USB connector, but with a round end.
Total 11

I would leave the components in their bags until you need each one, don’t just tip them out, or at the very least put them in two different trays so they don’t get confused.

If you’re new to soldering, I’d STRONGLY advise you build it with a friend or parent, to help you with checking the circuit and to share the excitement with as you turn it on for the first time and see it work!!! FIGnition is simple to build, as easy as many Lego® kits, but mistakes can be made and are harder to fix.


Setting Up

The next stage is to make sure you have your own equipment set up properly:

  1. Make sure you have a sponge for the soldering iron - and make sure it’s damp (not dripping).
  2. Turn on the soldering iron. For my temperature-controlled one, I turn it to about 3/4 of the way, otherwise just turn it on. Make sure the soldering iron is securely positioned, I wouldn’t leave it lying on the workbench; I’d put it on a mount and make sure the mount isn’t going to tip up.
  3. Get the rest of the equipment you need:
    1. A small 2-3mm wide flat-head screwdriver for levering out ICs.
    2. A fine-tipped pair of pliars.
    3. A wire cutter for snipping the component legs.
    4. A solder sucker (in case you make a mistake, which you probably will, since I sometimes do!)
    5. A decent amount of solder. I use lead-free silver solder: Ag 5%, Sn 95.5%, Cu 0.5%. I buy it from Maplin, a consumer electronics store in the UK.
    6. Possibly some extra lighting.
  4. For Testing the board, you’ll need some additional equipment
    1. A multimeter. I have a cheap one from Maplin. The only feature we’ll use is the short-circuit tester, the buzzer.
    2. A Standard USB A-B cable.
    3. A USB power source, for testing purposes I strongly advise using a USB power adapter, that plugs into mains as it is less of a loss than a computer if you have made a serious error.
    4. A Phono lead. (I assume most people have several in the house). An audio phono lead will do as long as it has phono plugs at both ends. Phono to scart is OK as long as you check the direction of the video is correct.

General Soldering Principles

The basic principle is this: solder from the lowest components to the highest ones. That’s because I’m assuming you don’t have any special PCBs clamps so you want to position the circuit in a stable way while you solder and the best way to do that is to solder components from lowest to highest.

Familiarise yourself with the basic soldering guide. There's some good tutorials at Lady Ada, except you really, really do pronounce it as SOLD-er in the UK (the wikipedia entry says it's "/ˈsɒldə(r)/ "). There's also a wonderful soldering guide from the UK which doesn't suffer from pronunciation advice: http://www.kpsec.freeuk.com/solder.htm. Soldering discrete components is fairly easy.

  1. Bend one end of the wire at right-angles using pliars fairly close to the component,
  2. Place in its hole,
  3. See where the other side should be bent and bend the wire with the pliars at that point. The resistors only just fit the component space so you’ll need to bend the wires very close to the components.
  4. Then you place the component in its location - the component should be on the front side of the PCB, the side with the “FignitionRevC markings”.
  5. Splay the legs out the other side - not too much (you don’t want them to touch the pins of other components), but enough to keep the component in place when you turn the PCB upside-down to solder it.
  6. Solder the component from the rear-side of the PCB as described below.. You don’t need very much solder at all on any of the pins.
  7. Snip the legs off the component and visually check that the solder joints look good - use a magnifying glass if you need to (see the general soldering guide).

Soldering the Board Together

  1. Solder the resistors first. There’s no best order, but I think doing all the same resistor values at a time is likely to lead to less mistakes. So, start with:
    1. the 1K5 Resistors (one at a time if you’re not familiar with soldering). They should go in: R1, R8, R10, R12, R14, R17. Then:
    2. the 1K Resistors which should go in: R4, R5, R9, R11, R13, R15. Then
    3. the 220R Resistors: R7 and R16.
    4. The 470R Resistor (from the other bag): R6.
    5. The 68R Resistors (from the first bag): R2 and R3.
  2. Solder the Diodes next. You have to be careful with the direction of the diodes. The black stripe should go on the same side as the vertical bar on the diode’s symbol on the PCB.
    1. The 2 Zener Diodes from the second bag (the bag with the USB connector). They go in D3 and D4.
    2. the 4 Signal Diodes from the first bag. They go in  D1, D2 (note: the black stripe is on the left); D6 and D7 (note: the black stripe is on the right) .
  3. The IC sockets are next. You need to solder in the sockets, but DON’T add the chips - you’ll only do that at the very end!
    1. Start with the 8-pin sockets since they’re the easiest.
    2. Place them in U2 and U3 so that the notch at the top of the socket points to the top and so that all the pins go through. If they fall out when you turn them up-side down, you may find that you can use something to hold them in place as you turn it but don’t use sticky-tape as it’ll melt during soldering, use a piece of thin stiff plastic or your screwdriver and then slide it out before soldering.
    3. Solder in the top-left pin and then the bottom-right pin of the socket. This will anchor the whole socket in place so you can solder the rest with ease.
    4. Solder in all the other pins.
    5. Next Solder in the 28-pin socket. Again the notch should point to the top. You’ll find it much more difficult to line up the pins so it goes through. Be patient; tease the legs into position, and don’t force it or you’ll bend some of the legs and make it more difficult. The rest of the steps are the same as above.
  4. The disc capacitors come next, they can go in any way round.
    1. Solder the 10nF capacitors C2, C5 and C6 into place, They are there to smooth out the power to the ICs.
    2. Solder the 22pF capacitors next in the locations for C3 and C4.
  5. The LED should go next. It has 2 legs. The shorter one should be on the right (the side that connects to R7). I find it quite hard to remember that the short leg is the -ve end, the cathode, especially hard if I'm reusing an LED which only has short legs. So, I often identify LEDs using an unofficial technique. If you look inside the LED casing you should see that one side looks like a flag. The Flag should go in the ground.
  6. The Switches can go in next. The switches look square, but the pins are placed at the sides of the switch. There will be a small section on the switches themselves in the Understanding It section of the web-site.
    1. Place them so they fit nicely in position, they’ll hold themselves into place when you turn the PCB up-side down.
    2. Solder them into place. Be careful, some of the switch PCB pads are very close together. You don’t want to connect across them or the keyboard won’t work. I’ll improve this in later PCB revisions.
  7. The Electrolytic Capacitor should go in next. The Stripe on the Capacitor says ‘-’ on it, that stripe should be on the opposite side to the ‘+’ marking on the PCB. In other respects, that Capacitor is easy to fit and solder.
    1. The USB connector should go next. Be careful with soldering the signal pins (the 4 pins arranged in a square) they are closer together than on the other components and don’t protrotrude very far through the PCB (they will protrude though). The side pads on the USB are an exception to the rule about not using much solder. Here you want to blob quite a lot onto those connections as they anchor the USB connector when you insert a USB cable - you need those connections to take all the force.
  8. The Phono connector is next.
    1. Use the wire cutter to make the plastic lugs on the bottom of the Phono connector a bit shorter. In future PCB revisions there may be extra holes to provide a better fix, but Phono connectors aren’t entirely consistant.
    2. Solder in the 3 pins on the Phono connector. There’s 4 pads, but the right-hand one isn’t used.
    3. Again, you’ll need quite a lot of solder here, the Phono connector also needs to be anchored well for when you insert the phono lead.
  9. The Crystal is the last component you need to solder into place, it’s very easy and doesn’t have a special orientation; it’s just very tall, so it’s last!

Wow - you’ve actually BUILT the computer now. And now comes the boring tricky bit, you need to meticulously check what you’ve done.

First you need to check all the joints... No, first you need to go away and have a tea-break. If you don’t have any tea, find a shop or store which sells it; buy some and have some tea! You need to take a break at this point!!! Take a break!!!

20 minutes later.. turn to the next section: Testing!
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Julian Skidmore,
20 May 2011, 09:49
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