Even if I didn't really finish this project and it actually failed, I wanted to share it beacause I see a lot of newbies (like me) on this great site and maybe I will help someone to avoid the same mistakes I did.
The Idea was to build a very simple 4-wheel robot, which moves forward, bumps into the obstacle, corrects it's direction and continues until it hits something else. For the traction I used the well known Tamyia double gearbox, in front I put some furniture wheels. For the body I used a plastic .box from wrenches as a base, not very estetic solution, but very robust with plenty of space.
My motivation was to learn how to work with microcontrollers and improve my circuit design skills. I was also hoping to build big enough platform (chasis) for future projects with enough room for extra sensors and actuators. I started this one at the beginning of the year and had already everything together, CPU was programmed, everything soldered together, it just didn't work and I didn't know why. Than for some time I didn't touch it until recently. Now I returned back to it to find a root cause and fix it if possible.
The first and biggest mistake I made was to put everything on one board (power and logic). The project couldn't be simplier, but I wanted to do everything by hand, including the H-Bridge and here is where I messed up with the biasing resistors. I figured that out now, but its easier to build a new circuit board than to fix the old one.
Second mistake was that I used wrong front wheels (like the ones on the office chairs). With the lightweight robot they just didn't turn and didn't change direction. For them I drilled 8 nice big holes in my plastic body so I practically damaged it and couldnt use it for another set of wheel(s).
The missdesign was to severe to fix, so I moved on to my next robot Berthold, which will have the traction gear box from his unfortunate older brother but hopefully better genes.
Good thing is that I discovered the magic of prototype boards (these things are just cool) and also I realised that it's not worth to try to reinvent the wheel so I will probably use an assembled H-Bridge module with L298N for the next projects and spend the saved effort for more interesting features.
Move forward, avoid obstacles
- Actuators / output devices: Tamyia Double Gearbox
- CPU: picaxe 08M
- Power source: 6xAA
- Sensors / input devices: two tactile sensors
- Target environment: indoor flat surfaces
This is a companion discussion topic for the original entry at https://community.robotshop.com/robots/show/arthur-my-first-robot-aborted-failed-project