While browsing for “goodies” on eBay I ran across a $9 robot chassis. How can you go wrong for $9? I haven’t built a robot since Talus my sumo Roomba, so I thought why not.
If you’re looking for something like the model I purchased, check out eBay and do a search for “Robot Chassis”. Adam Fabio of TheRegnineer.com mentioned he has almost completed working on a product that is similar. I’m guessing you can look for Adam’s product at his Tindie Store once he has finished it.
.. Fast forward three weeks for shipping from China.
None of my sensors have arrived but you’ll end up wanting to customize you robot for whatever sensor pack you are interested in anyhow. With that said I haven’t written any code for handling any sensors and at the end of the day this robot is just going to drive straight forward all day long. You can follow the code at the repository I set up for it on github to get the latest updates at…
I’m using the TAUTIC 20 pin PIC development board as it’s only $10 and takes care of the reset switch capacitor and comes on a nice plug-in board if you solder the connectors the same way I did. Use whatever you like but notice I’m using an internal oscillator so you don’t have to worry about getting a specific development board or having a crystal.
I’m also using the Pololu Quick 2s9v1 Dual Serial Motor Controller which is cost me $25, a little on the high side, but I had one from another project so I’m just re-using it and it makes life a lot easier for development.
Check out the photo at the bottom of the post for the basic schematic.
If you don’t already have MPLABX you’re looking at an upwards battle. However if you don’t mind watching a few YouTube videos it’s not up a creek.
1. Download and install MPLABX and the HI-TECH C compiler.
2. Start a project within MPLABX; selecting PIC 16F1509 and choosing the HI-TECH compiler, and create a main file.
3. Copy my code off the github site and drop it into your main file and compile.
You can download the free version of HI-TECH C and MPLABX which is also free. They are both obtained from http://www.microchip.com. MPLABX is an IDE (integrated development environment) which means it’s a program for programming, compiling and loading your software. HI-TECH is a C compiler which works with MPLABX. There are other programming language options such as BASIC and even assembly (I use assembly most of the time). I don’t know of any free BASIC compilers but I’m guessing someone has one. Google might be your best friend if you’re looking to go that route.
If you don’t have MPLABX you probably don’t have a PICKit 3 (or other hardware programming tool). I like the PICKit 3 because it will program all the newer Microchip PICs and it’s just about the most affordable tool for PICs. PICKit3 comes from Microchip or Digi-key. There are alternatives.
It took me about 30 minutes to put the chassis kit together last night. It was pretty obvious how it went together which was good because there were no directions. The encoder wheels don’t really attach other than compression, I see issues with that if I end up using them… that’s what you get for $9?
The code I put together this morning in about an hour or two after reviewing the manual for the motor driver online; you should also review this document. The idea with the code was just to test the motors and motor driver. I also selected a high/half/normal speed which you can adjust for your motor’s needs. I believe the highest speed setting you can select is 0x7F, I chose 0x4F for my high speed based on my anticipated desire. Adjust as needed.. but keep in mind your low speed should be set so it doesn’t stall on carpet or whatever you want your robot to be driving around on.
That’s about it for now. Once I get some sensors in I’ll add them and then write the code. I’m still new to C programming but I felt it was a better choice since it seems most popular; I usually write everything in assembler. Check out the photo I posted as it has a basic layout of the circuit and how I set mine up on a breadboard until I receive some prototyping PCBs I ordered.
…. to be continued