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Building the Polaron

zueblin edited this page Apr 16, 2019 · 17 revisions

1. Preparation

Check that you have all parts. Optionally clean the PCB and visually check it for damages. In addition to the parts and the teensy you'll need:

  • Good, bright light
  • A soldering iron with a rather fine tip
  • Solder (I use lead solder)
  • Diagonal cutters
  • Optionally a toothbrush to clean residual flux from the PCB after soldering (don't use for your teeth after that).
  • Optionally two blocks of wood as a aid when soldering the resistors
  • A USB 5-pin Micro-B cable to connect the teensy to your Computer

If you've never soldered before, you shouldn't build the polaron as a first-time project. If you still want to, check Adafruits Guide to Excellent Soldering.

2. LEDs

Lets do the LEDs first. Its generally a good idea to start with the flattest parts first and do the bigger parts later, so they don't get in the way. The LEDs are temperature sensitive, its recommended to not heat them up for more than a few seconds at a time. The orientation of the LEDs on the PCB is important, make sure you place it, so that the small triangle on the LED is in the same corner as the small (1mm) extra line of the part diagram on the PCB (top left corner in the image below).

My preferred way to solder these LEDs (and Surface Mount Devices, SMD, in general) is to only solder one connection at the beginning, then correct the position of the part if necessary, and then solder the rest of the connections:

  1. Place a small dot of solder onto one of the pads (i use the pad with the small 1mm line for this)
  2. Now place the part and press it down firmly
  3. Reheat the dot of solder and press the part down. The part is now in place and should stay in position. Correct the position if necessary by reheating the solder, but be careful not to overheat the LED. Make sure the LED is centered exactly with regards to the pads, if you use too much space on one side, it will be hard to solder on the other side.
  4. When your happy with the position, solder the remaining three connections of the LED

Solder all LEDs like this (I do the circular LEDs first, then the others). With a total of 120 points to solder its easy to forget some, so you might want to check all connections now.

3. SMD Capacitors

Soldering these two buggers is a bit tricky, as they are small as hell and if you don't use pliers you might burn your fingers (thats part of the fun). I use the same technique as for the LEDs, i.e. apply a small dot of solder onto the pad first and then reheat it to 'glue' the part onto the PCB. Then solder all connections.

4. Resistors

Congrats, you've done the hard part, the rest is peanuts. Lets continue with the resistors. PRO TIP: Since we are extremely concerned with aesthetics, make sure to use the same orientation for all resistors (as you most certainly know the orientation of a resistor is irrelevant from an electrical point of view). If you thought you'd use the two blocks of wood to make some beats, your wrong. THIS is what you need them for:

  1. Place all the resistors into the holes
  2. Solder: Normally, after sticking the resistors into their holes, you would turn the PCB upside down and solder the parts on the bottom side of the PCB. However i found that soldering them on the front side of the PCB has the advantage that the resistors are nicely held in place by our friend gravity (thanks for that) and in addition, since the bottom side stays fresh and clean when soldering like this, its easy to cleanly cut the remainder of the legs of at the bottom side afterwards (which is what you'll do after soldering all resistors).

5. Pushbuttons

Soldering pushbuttons is rewarding and easy: Enjoy the nice click when you put them in place and solder all legs on the bottom side of the PCB

6. Audio Plug

Not much to write here. Put the Audio-Plug in place, heat the pad and the plug connector then apply solder (don't save on solder here as this part might be physically stressed a bit, when plugging/unplugging audio cables)

7. Shift Registers

Next are the shift registers, which are needed to read out the pushbutton state. Make sure you solder them onto the bottom side of the PCB and not the top. Plus, the orientation needs to be correct, see picture (there is a small marker on one of the short sides of the chip, which needs to match the same marker on the part diagram on the PCB)

8. Teensy with IC Socket

Its not easy to get a 48 pin chip into an IC Socket. It might need some force. I found that its easier to put the Teensy into the IC Socket, before soldering the Socket onto the PCB. For this, put the socket into the black isolation foam that comes with the teensy when you buy it and then press the teensy into the socket by carefully applying force from above.

After that, place the Teensy/Socket onto the BACK of the PCB. Make sure you position it according to the parts diagram on the PCB (there is a marking for the USB Plug and one for the SD card slot as reference). Flip the PCB and solder two diagonally positioned legs of the IC Socket first (eg. the top left and bottom right leg). Before soldering all other connections, make sure that the IC Socket is completely flat on the surface of the PCB (this is very easy to correct, as long as you only have two soldered connections, but almost impossible after you soldered all connections)

9. Potentiometers

Last not least solder the two potentiometers. Thats it, we're almost done. Now is a good time to clean the PCB using a toothbrush (which you should use only for things like this afterwards..). Then use the two small screws to attach the standoffs on the bottom of the PCB.

10. Done

Well done! Now go wild, have a beer or two, party, share some images and text your friends!

11. Uploading the firmware

Now its time to Upload the Polaron firmware onto the teensy.

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