Rav4-tcu

The TCU circuit board

One 2-layer board, 200 × 170 mm, that plugs straight onto the Arduino Mega and carries the whole TCU circuit. You order it bare and solder the parts in yourself (build book, parts 4–6): every connection between the parts is already a copper track, so there's no wiring on the bench.

Ordering it

Upload rav4-tcu-gerbers.zip as it is (don't unzip it) to a board maker such as JLCPCB, PCBWay, OSH Park or Aisler. Their website reads the size and the number of layers from the zip. Pick these options:

It costs about $20–40 for five boards, shipping included, and arrives in 1–2 weeks. Boards over 100 × 100 mm cost a bit more at some makers. That's normal. Before you pay, look at the maker's preview of the board: it should match the picture above, with a notch in the back-left corner and 5 mounting holes.

What's in this folder

The shopping list has every part with where to buy it. The build book's six soldering steps say which parts go in at each step.

About the design

• It is generated. tools/pcb.py builds the board from the tested circuit in tools/boards.py: it places every part, routes every track with tools/pcb_router.py, fills both sides with ground, and refuses to write anything if KiCad's design-rule check finds an error or an unconnected pad. It needs KiCad 7's Python module (python3 tools/pcb.py). Don't edit the board by hand: change the script and run it again. make check then checks that every pad is on the net the circuit says.
• Made to be easy to solder: through-hole only, with big pads (a 0.6 mm copper ring round each hole where there's room, long oval pads on the chips), every part's name and value printed next to it (RU11 2.2k, DI1 1N4148…), the Mega's used pins labelled, every screw terminal labelled with its signal, sockets for the two bigger chips, and no ground pad joined solidly to the ground copper (those soak up the iron's heat).
• Tracks sized for the current: 1.5 mm for the solenoid supply, 1.0 mm for the solenoid, dummy-load and 12 V lines, 0.8 mm for the relay coils and the 5 V rail, 0.4 mm for signals.
• The screw terminals run along the front edge in the same order as the box's glands: SHIFT, DASH, SCREEN, ATF, SIG, PWR, SOL, LOAD.
• The Mega sits underneath, joined by plain male header strips soldered into the board. A notch leaves its USB and power jacks free.
• 5 V comes from a fixed RECOM R-78HB5.0-0.5 regulator (9–72 V in): nothing to adjust.

Nothing has been made from these files yet. The first board you build is the first test of the layout: check it carefully, step by step, with the build book's meter checks, and see the system review §8.

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RAV4 TCU by gamer927 · CC BY-NC-SA 4.0: free to build, not to sell. That includes the board: you may have boards made for your own build, but not sell them.