5 Replace the 27k in the lower leg of the AP3012 comparator circuit with a 56k
6 to drop the voltage from ~27V to just under 12V.
8 In the AP3012 circuit, rotate the inductor and 4.7uF caps 90 degrees, and lift
9 pin 5 of the IC, to detach all of them from the 3.3V rail. Use a wire to
10 connect all of them to pin 4, the gpio driving the circuit.
12 The net effect is that we're making 12V from the gpio, which means all the LED
13 current and switcher inefficiency is coming as current through that gpio. The
14 measured LED current is around 7mA, so this is "safe" for the SOC, but leaves
15 less engineering margin than we usually like.
17 Changing the circuit to be powered from v_lipo with the gpio hooked to shdn*
18 and controlling a FET switch on the output might be smarter someday?
21 - what gets through-hole soldered on to a v2.1 board (sans optics)
23 6-pin micromatch with locking ears
24 2 * 9-pin screw terminal strips
25 5x1 100mil straight header
29 2x1 100mil right-angle header
32 - the LCD digits we've used, Lumex LCD-S101D14TR, are only available now if
33 we're willing to order 3150 pieces at !.85 each or $5,827.50. That's just
34 not reasonable when we only need 3 per unit and a big build might be 35
37 - DK and Mouser both have the Varitronix VI-611-DP-FH-W in stock. This is a
38 6-digit LCD display whose digits are 25.4 mm tall instead of 34.54. This
39 LCD module would require the PCB width to grow an inch in width to 5.5
40 inches. A quick look at the FreeCAD file suggest this is manageable without
41 a complete re-design of the panel. By using the panel to only expose 3 of
42 the digits, we could mimic the existing functionality. At $16.27 for q5
43 and above from Mouser, this seems like a credible way of making more TeleLCO
47 - we should have 31 SOC left after TeleMega v6.0 build if all goes well, which
48 means we should target a batch size of 30 boards.
50 - 1170NF in orange is hard to get. The part number is 1170-001-150.
51 mteagleent.com seem willing to sell me 30 pieces for $1,520.40 plus $15.00
52 shipping. Pounce on it?