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737 Overhead Panel I/O Controller V2

3 years ago 1532
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This is a mother-of-all interface boards I designed for my 737 overhead panel. Features:

  • Raspberry Pi Zero W as the microcontroller, pluggable into the PCB (Note: Male Pins soldered BELOW the Pi, not above).
  • 192 switched inputs (expandable to 256)
  • 128 LED outputs (expandable to 224), up to 70mA per channel, current limit controllable in groups of 16 (no resistors needed)
  • 16 channel PWM outputs for controlling servos
  • 48 7-segment character displays
  • 8 14-segment alphanumeric displays
  • 24 GPIO, interruptable
  • 8 channel analog inputs
  • Optional Real-Time Clock
  • Original RPi GPIOs exposed for future expansion

Wiring is via 2x8 headers, so you can used 16-wire ribbon cables and easy-to-crimp IDC connectors at the controller end. For the panel end you can either strip the ribbon cable and solder direct to components, or attach a connector as appropriate.

Testing is not complete. I will update here as I check and build up the software.

Project blog is at

Change History:


  • Matrix: Some of the diodes were in the wrong positions. The V2.2 board works, just that the diode was not next to the pins it serves. Fixed.

V2.2 (what I use)

  • Fixed Trimmer Pot connected wrongly, using max, instead of needle.
  • Fixed HT16K33 module too narrow.


  • place a dot on header pins to indicate pin 1 location.
  • Fixed P29 label obscured
  • Add a GPIO controlled LED.
  • Fixed buzzer should be active type, needs a transistor and current limited LED.
  • Fixed serious problem with pi connector:
    • Pi headers reversed, original PCB component was meant for it to be mounted upside down.
    • GPIO numbering wrong, assumed W.Pi numbering whereas component was BCM.
  • Added socket for holtek HT16K33 module (removed two MAX7229CNG).


  • initial version


737 OVH2 Digital Switch Input

737 OVH2 PWM

737 OVH2 CPU

737 OVH2 Segment & Rotaries

737 OVH Analog Inputs

737 OVH2 Annunciators (DM13A)

737 OVH2 PCB


ID Value Qty. Package Components
1 MCP23017-E/SP U1,U2,U90,U91,U20 DIP28 (300) 5 Yes
2 1u C1,C2,C900,C92,C90,C93,C94,C95,C96,C97,C91 RAD-0.1 11 Yes
3 1N4148 D1,D2,D3,D4,D5,D6,D7,D8,D9,D10,D11,D12,D13,D14,D15,D16,D17,D18,D19,D20,D21,D22,D23,D24,D25,D26,D27,D28,D29,D30,D31,D32,D33,D34,D35,D36,D37,D38,D39,D40,D41,D42,D43,D44,D45,D46,D47,D48,D49,D50,D51,D52,D53,D54,D55,D56,D57,D58,D59,D60,D61,D62,D63,D64,D65,D66,D67,D68,D69,D70,D71,D72,D73,D74,D75,D76,D77,D78,D79,D80,D81,D82,D83,D84,D85,D86,D87,D88,D89,D90,D91,D92,D93,D94,D95,D96,D97,D98,D99,D100,D101,D102,D103,D104,D105,D106,D107,D108,D109,D110,D111,D112,D113,D114,D115,D116,D117,D118,D119,D120,D121,D122,D123,D124,D125,D126,D127,D128,D129,D130,D131,D132,D133,D134,D135,D136,D137,D138,D139,D140,D141,D142,D143,D144,D145,D146,D147,D148,D149,D150,D151,D152,D153,D154,D155,D156,D157,D158,D159,D160,D161,D162,D163,D164,D165,D166,D167,D168,D169,D170,D171,D172,D173,D174,D175,D176,D177,D178,D179,D180,D181,D182,D183,D184,D185,D186,D187,D188,D189,D190,D191,D192 DO-35 192 Yes
4 Header-Male-2.54_2x10 P13,P81,P82 HDR-10X2/2.54 3 Yes C62032
5 cc9d98028b7c0a691544c90de901bac7 P72,P73,P70,P71,P68,P69,P62,P63,P64,P65,P66,P67,P50,P51,P52,P53,P54,P55,P56,P57,P58,P59,P60,P61,P100 HDR-8X2/2.54 25 Yes C68234
6 PCA9685 16-Ch 12-Bit PWM Driver Module PCB2 PCA9685 16-CH 12-BIT PWM DRIVER MODULE 1 Yes
7 KF124-3.81-2P P79,P80,P83 KF124-3.81-2P 3 Yes C69811
9 active buzzer 2300Hz BUZ1 ACTIVE BUZZER 1 Yes
11 3mm green LED1 LED-3MM/2.54 1 Yes C73643
12 330R R80,R81 AXIAL-0.3 2 Yes
13 8a6f828e8a2233e5136da005d68a73ac P84 HDR-5X1/2.54 1 Yes
14 3mm yellow LED2 LED-3MM/2.54 1 Yes C73643
15 f61408099734479e97024cb2018873fb Q1 BC547 1 Yes C2092
16 1k R83,R305,R306,R307,R308,R309,R310,R301,R303,R20,R21,R22,R23,R24,R25,R26,R27 AXIAL-0.4 17 Yes
17 MCP3208-BIP U900 DIP16 1 Yes
18 Header-Male-2.54_1x8 P901,P900,P902 HDR-8X1/2.54 3 Yes C49256
19 MAX7219CNG+ U92,U93,U94,U95,U96,U97 DIP24-2.54-30.6X7.62MM 6 Yes
20 Header-Male-2.54_2x8 P93,P94,P95,P96,P92,P97,P98,P90,P91 HDR-8X2/2.54 9 Yes C68234
21 1.5k R302,R304 AXIAL-0.4 2 Yes
22 c7826df95d76418aa4924df48d5068a5 U98 ADAFRUIT 16X8 LED MATRIX DRIVER BACKPACK - HT16K33 BREAKOUT 1 Yes 1427
23 dedd8d19d288cc4b434967eda0df580a P99 HDR-4X2/2.54 1 Yes
24 DM13A U21,U22,U23,U24,U25,U26,U27,U28 DIP24 8 Yes
25 0.1u C20,C21,C22,C23,C24,C25,C26,C27,C28 RAD-0.1 9 Yes
26 22K PR20,PR21,PR22,PR23,PR24,PR25,PR26,PR27 RM065-V1 8 Yes C54661
27 Annunciator 1 P14 HDR-8X2/2.54 1 Yes C68234
28 Annunciator 2 P15 HDR-8X2/2.54 1 Yes C68234
29 Annunciator 3 P16 HDR-8X2/2.54 1 Yes C68234
30 Annunciator 4 P17 HDR-8X2/2.54 1 Yes C68234
31 Annunciator 5 P18 HDR-8X2/2.54 1 Yes C68234
32 Annunciator 6 P19 HDR-8X2/2.54 1 Yes C68234
33 Annunciator 7 P20 HDR-8X2/2.54 1 Yes C68234
34 Annunciator 8 P21 HDR-8X2/2.54 1 Yes C68234
35 LED+ P27,P28 HDR-8X2/2.54 2 Yes C68234
36 Ann. Ext. P29 HDR-5X2/2.54 1 Yes


Filename Download
Gerber_737 OVH2
Gerber_737 OVH2
Gerber_737 OVH2
Gerber_737 OVH2


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