Intro to CAD
This page is for the Intro to Engineering ENGR 122 EE/CPE Section
Two Dimensional CAD
- DraftSight is an AutoCAD clone. Presently it is rather like AutoCAD 2006 or 2007.
- Orthographic Projection (Front, Side and Top View) Drawing Tutorial
Persistence of Vision Bike Light Project
This project will use a 3.3 volt Arduino Pro Mini clone that you will design the circuit board, housing, and software for. Persistence of vision is a psychological effect that allows you to see two dimensional images that were created by one dimensional flashing LEDs. Here are some similar projects:
- This is video shows some POV projects from Japan.
- Arduino on a breadboard spinning with a motor.
- Another spinning POV display.
- Simple Code for a simple POV device using the Arduino.
- Another simple Arduino POV device with understandable code.
- A POV wand with 20 LEDs, and fairly understandable code.
We will have an MMA8452 accelerometer that communicates via a serial I2C interface. The accelerometer will measure the angular acceleration, which will allow the velocity of the bike wheel to be calculated. This will make it possible to flash LEDs at the proper time intervals to spell words, draw pictures, etc., as you ride your bike down the road at night.
The power source for your POV device can be two or three AA, or AAA batteries. You need to design the packaging. Some suggestions that you can consider are:
- Use clear vinyl tubing and corks in the end to house the circuit board, and tie wrap it to the spokes on your bike.
- The LEDs we purchased are 20 mA with a forward voltage drop of 2.3 volts, and there are some restrictions on the currents you can draw from the ATMEGA328P shown here.
- Schematic of the accelerometer from Sparkfun
- Schematic of the Arduino we are basing this from
Kicad Libraries
- MMA8452Q Accelerometer EESchema library
- MIC5205 Voltage Regulator EESchema library
- Battery EESchema library
Footprints for CVPCB and PCBNew
- Use the BAT-AA-BK92 footprint
- This is a document telling about the QFN footprints.
- This library (Aerodyne_v2.pretty) has all the special footprints we need.
- This is the board outline drawing. You can import this into PCBNew, using File->Import->DXF File.
EESchema Checklist
- ATMEGA328P
- MMA8452Q
- MIC5205
- Do you really want an LED to tell you the device is on? (I'm guessing probably not, so make sure you didn't put one in if you don't.)
- Batteries
- Programming cable connector
- LEDs
- Are the LEDs distributed over Ports B, C and D?
- No errors in the design check?
- Do you have the DOC linked to the datasheet for each important part?
- Do you have the datasheet URL in the datasheet field for each important part?
- Does your schematic look need and tidy?
- Do you have pull up resistors on the I2C bus lines SCL, SDA, and SA0?
CVPCB, Associating Footprint Patterns with Parts
- Start CVPCB from EESchema after completing the design rules check and creating a netlist.
Example Schematics & Footprints
- This is an example schematic. It has provision using jumpers K1 and P3 to select either two or three batteries and a voltage regulator, or two batteries without a regulator. You don't need to do this. I am doing it, so I can have a board that can be configured either way for debugging possible issues. I recommend picking one or the other power supply method.
- Example Footprint Selection You need to select the Aerodyne_v2.pretty in the Preferences->Library Tables in CVPCB in order to find the special footprints.
