I started all of this back in July 2009. I knew this project was coming up so I decided to get a head start and find out exactly what was entailed in building a robot and to see if it was within the scope of my abilities. I have a long experience with electronics and some experience with the components of robotics so this is not all new to me. In a way I have built a robot before when I constructed an animal feed system for dairy cows which was computer controlled and involved data logging. That system was DOS based and used the parallel port to control the entire thing.
My son has had a K-9 toy hanging around the house for some time. The remote control for this was lost some time ago so it was effectively useless. The first thing I did was open up K-9 and take a look around. The toy takes 4 AA batteries meaning it operates between 4.8 to 6 Volts DC (NiMH or Alkaline), there are two motors and a control PCB.
The only thing I could make K-9 do was make sounds by pressing the demo button so I rigged up an audio lead to plug into the line-in input of a PC to record the sounds. I added an inline resistor to protect the input and also to help avoid an impedance mismatch which would result in clipping of the sound.
This lead was plugged into a nearby PC and the sounds recorded using Audacity. I would keep these for future use.
After this came lots of research into background. Also I looked into small factor PC systems including Mini,Nano and Pico ITX systems. With the limited space available and also to keep wattage down my main interest focused on the Pico ITX systems available from VIA with a tiny footprint of just 7.2 x 10cm.
I already own a 4GB compact flash card and IDE adaptor and have experience with embedded systems so acheiving the integration of this tiny little PC would not pose much of a problem. It was originally intended to use the existing chassis of K-9 with its motors and power them from the 5V supply line of the PC but as more recent developments have shown this simply wasn't up to the job so a dual supply will more than likely be used with a supply for the logic and PC and a separate supply for the dirty components like the motors and any other inductive devices.
As for batteries there was only one option - LiPo. lightweight and with a huge energy density these batteries are great for this project. NiMH and lead-acid were the other options but have been disregarded. NiMH dont have the energy density required to keep the robot going for a long time and lead-acid are simply too heavy and cumbersome. LiPo poses its own problems with critical voltages having to be observed to avoid damage and a more complicated balanced charging system.
I didn't spend too much time looking at sensors. I have come across the infra-red range finder modules before and decided to take a closer look. After considering the alternatives very briefly I decided to stick with what i know and trust which are the Sharp range of IR range finders.
and that brings me up to October which strangely enough is where the previous post starts. Sorry for jumbling up the order a bit.
I am now onto circuit diagrams for the drive system.
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