Assembly notes for RFX Teensy 3.x carrier board

Transcription

1 Assembly notes for RFX Teensy 3.x carrier board Mark Pendrith Dec Basic kit parts (BOM) 1 PCB mount 5mm/2.1mm DC barrel jack (see note below) 1 LD1117v33 1 1N5817 Schottky diode 1 0.1uF cap 1 10uF cap 1 2x3 header (m) 2 2x4 headers (f) 1 1x5 headers (f) 1 1x13 " " 1 1x14 " " 3 1x6 " " 3 1x8 " " 1 1x10 " " 1 1x18 " " Optional (for Teensy 3.x underside pad break-out): 1 2x7 surface mount male pin header 1 2x7 low-profile female header Optional (if using breadboarding headers): 1 1x6 long pin headers (m) 2 1x8 long pin headers (m) 1 1x10 long pin headers (m) Optional (if using stacking headers): 1 1x6 stacking pin headers (m) 2 1x8 stacking pin headers (m) 1 1x10 stacking pin headers (m) 1 2x3 stacking pin headers (m) Notes: Single-row female pin headers supplied as four 1x40 strips of pin header, and the correct lengths need to be cut from these longer pieces. (Only three strips are actually required if cutting to scheme below; the additional strip is provided in case of errors.) For the latest version of the board, provision has been made for a PCB mount DC barrel power jack can be mounted under the Teensy as an option. The part required is a standard 5mm/2.1mm 3 tab barrel jack, modified to remove the side tab, leaving two tabs used to mount the part. See the additional notes at the end of this document for more details.

2 Suggested cutting scheme for 40-pin female header strips Strip one is cut to provide 1x13, 1x5, and 3x6 headers pieces, like so: the gaps indicating which pins have their "tuning fork" inserts removed in order to make the cut. In this case, there is zero waste header. Strip two is cut to provide 1x10, 1x18, and 1x8 headers pieces, like so: w the gaps again indicating which pins have their "tuning fork" inserts removed in order to make the cut. In this case, there is 1 pin of waste header left over (indicated by "w"s) Strip three is cut to provide 1x14, and 2x8 headers pieces, like so: wwwwwww the gaps again indicating which pins have their "tuning fork" inserts removed in order to make the cut. In this case, there is 7 pins of waste header left over (indicated by "w"s). To remove the "tuning fork" inserts, simply grab the end of the pin, and pull. The trickiest thing is getting hold of it, small pliers are recommended (I ve found I can also use the same cutting pliers I use for trimming leads on through-hole components just as well.)

3 With a small tug the pin insert comes out cleanly. If you've miscounted and pulled the wrong insert out, no problem, simply reinsert. To cut the header strip at the removed pin, use a stout sharp bladed "Stanley" knife/box-cutter or similar. Press on one side of the strip just enough to start a cut (you don't have to cut all the way through).

4 turn over and press on the other side. The strip should just break where you are pressing with the blade (the other side has already been weakened by the scoring.) To clean up the edge (optional, but looks nicer!) hold the cut strip upside down on the table or cutting surface, pins facing up, and trim the excess off the cut edge cutting straight down with the cutter blade.

5 A nice sharp blade here really helps. Two or more passes to shave the edge nice and flat usually produces the cleanest result. When you stop seeing the groove which was the cavity that held the pin insert, stop... you don't want to cut through to the next cavity! And be careful to keep your fingers out of the way! (Just grip the piece in the middle/far end rather than near the cutting end.) You should end up with the following cut pieces (also shows two waste pieces):

6 The photo below shows cut pieces sitting in position on PCB, not yet soldered in. (Note: original version of board is shown below). A tip for the simplest arrangement of the 14, 6, 13 lengths that form the socket for the Teensy is to find the 6 length piece that has a manufactured edge, and use this to butt against the 14 length piece. Similarly, use the manufactured edge of the 13 length piece to butt against the 6 length piece. Note also the 5 length inside piece that completes the socket. The cut pieces for the secondary grid-aligned headers are shown unmounted, with the gender changer male-male pin header pieces. Note that if mounting these grid-aligned header pieces under the board, it is slightly easier for access to solder in these headers before soldering the Arduino layout shield header pieces on top.

7 Schottky diode and caps Also in the photo is shown the position of the Schottky diode between Vin and Vusb (Vin - <- Vusb), and also the decoupling 0.1uF cap between the header pieces. If required, the 10uF electrolytic filter cap can be connected to 3v3 (middle pin of the LD1177v33 voltage regulator) and Gnd (inside pin of the voltage regulator). Mounting in the two holes in the prototyping area immediately in front of the voltage regulator is the simplest place to position this, bending the leads back to the voltage regulator solder pads underneath to connect. ICSP header Note that the 6-pin ICSP header only has four pins connected: MISO, MOSI, SCK and Gnd. The reset and Vcc pins are not connected to anything by default. If you wish to supply power to a shield via the ICSP header, you will have to decide on the appropriate connection (e.g., 3v3 rail, 5V (Vusb) rail, Vin, or other arrangement. IOREF pin Similarly, the IOREF pin on the power header is not connected by default, but can be connected as required on an ad hoc basis. Screw terminal block If mounting a screw terminal block (or similar) for external 5-12VDC Vin power supply, connect the designated + terminal on the block directly to a Vin connection point (e.g., Vin pin on the voltage regulator), and the other terminal to a Gnd connection point (e.g., Gnd pin on the voltage regulator). 5mm/2.1mm DC barrel jack & 2x7 pad header (new board design) On the latest version of the board is provision for mounting a barrel jack for Vin input, as an alternative to the screw terminal block described above. A standard 3 tab 5.5/2.1mm PCB jack is used, but is modified by removing the side tab (the switched ground connection.) To remove the side tab, it is a simple matter of bending back and forth a few times, until it snaps off flush and neatly from metal fatigue:

8 Below is the newer board design with the modified barrel jack. Also shown is the optional 2x7 low-profile header piece, which can be used to break out the additional Teensy 3.x IO pins broken out on pads on the underside of the Teensy board. The modified jack and low-profile header piece shown positioned on the board:

9 If using the 2x7 header for access to the pads, a matching male SMT 2x7 pin header needs to be soldered onto the bottom of the Teensy 3.x. Photo above shows the SMT 2x7 male pin header soldered in place. Note: If soldering this SMT part onto the Teensy, it is suggested to do this before soldering in the through-hole pin headers around the edges. This makes access to the pads with a fine-tipped iron much more straightforward. Advice for aligning the piece is to center the legs on the pads by eye as accurately as possible before soldering. That will result in accurate alignment with the corresponding lowprofile female header on the carrier board.