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Table of Contents
During the 2018 season, we hand-wired a little board to break out and debug the Digital I/O wiring to the break-beam sensor. This project is about a PC Board to replace that, and for other DIO testing and wiring.
* Review DIO (Digital I/O) in the roborio digital IO section.
Here's a perfboard prototype and a sketch of what we're building (click for a bigger image):
We might or might not include the test button.
What's on this board:
- Connectors
- * Female 3-pin socket for cable to RoboRIO
- * Male 3-pin header to connect to switch, device, or sensor.
- Yellow LED indicates that power is present on the DIO cable. This is an instance of a Basic LED circuit
- Red LED lights when the signal is “low”, perhaps because it has been connected to ground by a switch or sensor. This is a slight variant on the Basic LED circuit
Not on the prototype, but hinted on the shematic: additional male headers. The break-beam sensor needs two things wired up: the source and the detector. Sometimes we won't install the actual headers, but will just solder individual wires into the holes - but we can still use the same fabricated board blank.
Schematic
Before reading this section and studying the DIO tester schematic, you might want to review:
- Introduction to Electrical Schematics
The schematic and board files for our design is in our github
Here's a screen shot of the complete schematic:
(TODO picture)
On the schematic are:
- a basic LED circuit that lights up yellow if the +5v power is present and connected.
- a slightly modified LED circuit that lights a red LED if the signal wire is LOW (connected to ground)
- Four connectors: one socket for connecting to the RoboRio, and three headers for sensors.
The LED for signal-is-LOW
The Printed Circuit Board Design
We followed the steps in our kicad tutorial to design the copper traces on the board.
Our first order of 6 boards was done at oshpark. The project is here: https://oshpark.com/shared_projects/UVZvYEPw