Autodesk CAD modeling

My initial project with embedded systems/MCUs was to create an automated vehicle. Realizing that my algorithm was too simple too implement, I wanted a real challenge. I decided to create a PC controlled robot. How exactly it will be controlled will be revealed once I get some results. Right now, I wanted to do some CAD modelling/stress and FEA analysis for the prototype.

Seeing as to how I only had experience in CAD since my first year of university, the experience was fairly new but all the terminology and methodology came back really quickly!

If you are a student and have a post secondary school email, I highly recommend you register at and download a FREE version of Autodesk Inventor Professional (the company’s flagship product is AutoCAD).

As I said, coming back to CADing was fairly frustrating for me as it was a long time ago for me. Once I started to get a hang of it, it was quite intuitive though. One thing I am concerned about is the misconception of CAD. It simply isn’t just a tool to generate parts (though it is a major part of it!), but it is a tool to simulate a device’s operation and behavior before real world creation so that you don’t run into any surprise problems during construction. If you are not defining/constraining degrees of freedom as in the real thing you are making, some people would argue you’re just drawing, not designing!

Here’s a little demo of what I cooked up after familiarizing myself again with CAD. You can see that the arm has the intended movement and constraints in desired parts. Components shown are Servo’s for joint movement and planned arm parts using actual dimensions. I’d like to make a quick tutorial of my approach once I have enough time to properly do it.

NOTE: I AM NOT A CAD PROFESSIONAL. If I there is any incorrect methodology or terminology I am using, let me know and I will correct myself!

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PIC Serial Communication Pt.1

Hello to anybody who may ever read this. Looks like this “blog” will serve purposes for my ramblings about electronics/engineering as well as containing simple, quick tutorials on embedded systems.

First up will be a quick tutorial on PIC Serial Communication. The explanations on what Serial Communication is and how it works is very detailed; you don’t need me regurgitating it.

Why do this for a project over using an Arduino’s integrated USB communication? For me, it was the learning experience using PICs. Also as an engineer, I felt my hand was held to do each and every little task; you don’t get into the nitty gritty of things. Don’t get me wrong, Arduino is fantastic if you want to get things up and running quick. I’ll leave this rambling for another day.

Let’s get started. Here is the list of materials you will need. My aim for materials was to be as cheap as possible. No need for already made USB – to – TTL boards or anything else fancy:

  1. USB – to – RS232 cable (RS232 ports are obsolete; all computers now have USB ports)
  2. MAX232 chip (Down shifts 12V from RS232 to 5V for PIC)
  3. Four 1uF capacitors and one 0.1uF capacitor
  4. RS232 port (Also called DB9 port; female/male depends on your cable)

The particular MAX232 chip I am using is made by STMicroelectronics and is coded ST232CN.

The DB9 port has 9 pins. You only need to hook up 3; transmit on pin 3 (Tx), receive on pin 2 (Rx) and ground on pin 5 (GND).

I am using the PIC16F690, the connections will obviously different if you are using a different MCU. The idea is the same, however. On the 16F690, Tx is on pin 10 and Rx is on pin 12.

Observing the ST232CN datasheet (page 4/15), out to RS232 goes to pin 14 and in from RS232 to pin 13. Out to MCU to pin 12 and in from MCU to pin 11.

The circuit schematic in Figure 1 explains all this better:

Serial Communication

Figure 1

Figure 2

Since this post is a little long, I’ll end it here. Since I’m trying to explain everything as quick and as straight forward as possible, I’ve left a lot of detail out. If you’d prefer more detail, leave a comment asking your question and I’ll revise the way I explain things in future posts.

Here is a little treat to look forward to:

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