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Arm Box PCB V2
Documentation

Sonia Ly

Task Overview

  • Modify the design of last year’s Arm Box PCB to include:
    • Edge Card connector slots to slot in the new ESC Carrier Boards
    • Add a toggle switch to turn on/off the fans
    • LED to indicate if an ESC is in or not
  • Modify the layout to:
    • Make removing and inserting connectors easier
    • Change the Top → Bottom order to Elbow → Shoulder → Waist (instead of S → E → W)

PCB Information

  • Size: 100x70mm (Same as last year)

Signals coming out of the ESC
5 Power Signals:

  • Phases A,B,C, rate for ~20A if possible (3 connections here)
  • Power and Ground, rate for ~20A (2 connections here)

12 Data signals:

  • 5 Encoder signals: 5V, GND, A, B, Z
  • 4 Limit Switch Signals: EXT_INT1, EXT_INT2, GND, GND
  • 2 CAN Signals: CAN_H, CAN_L
  • GND extra

Choosing an Edge Card Connector
When choosing an Edge Card connector, I made the following assumptions:

  • The new ESC Carrier board would be a 4-layer board
    • (For reference, JLC PCB’s average 4-layer board thickness is 1.6mm)
  • We want the cheapest option possible
    • (so getting the connector from Molex would be a big +)
  • Ideally, want don’t want a connector that’s too long
    • (around the width of an ESC, ~30mm)

The best option I could find that fit most of those criteria was combining the 2 following edge card connectors:

TypeGuides?Female (Sonia’s side)Male right-angled (James’ side)
4PW + 12SIGYes461144120459854413
No461144121
2PWYes461120203 Cannot be sampled for free!459852932
No461120201

Useful Links

Personal Notes

Changes:

  • Make the board longer, horizontally
  • Deal with all the CAN changes
  • Adjust Layer stack
  • Net tie

Changes to be made:

  • 4 pos connectors for lim switches
  • Extra switch for can termination
  • Make the connector that goes to the brushed board on top (consider putting it on the other side)
  • Switch phase c is 24 v actually
  • Make the fuses more accessible
  • TODO: DOUBLE CHECK IF CONNECTOR ORIENTATIONS ARE CORRECT (not a concern whoops)
  • Fan connectors on the side perhaps
  • Via to probe gnd
  • on/off indicator for switches
  • Clean up molex connector sheet
  • Adjust layer stack
  • Review connector thickness and if it interferes with anything (perhaps just add the 2d model

Modifs to make:

  • Go the can stuff on layer 4
  • Make
  • Change pinouts on connectors to make life easier

Distance between 2 pins:

Questions:

  • Does signal GND always have to be different from power GND? Why?
    • Prevent interference?
  • Are the limit switches tied to signal gnd or power gnd
  • How to implement CAN termination lol

NOTABLE CHANGES TO REPORT:

  • Net label change of lim switches