To drive all 6 engines of the same H-bridge is not recommended, it tends to get hot, pretty hot. I was thinking of make a extension card with three H-bridges on it, but then I’d have some weight issues with my bot, it has to weigh less then 500g. The solution was to build a new PCP with htree H-bridges.
Because I never have created a PCB before I was a little bit unsure of how to do it and if I would do any errors. But I’d much help from folks at CRF and it turned out to be a win!
All my resistors and LED’s is surface-mounted so I was a little bit worried that I would have problems while solder. I then watched “Surface Mount Soldering 101″ from CuriousInventor.com and started solder, it turned out to be very easy.
The Pirate cars PID-regulator get’s goal-value from a tachometer inside the gearbox. A IR-reflex-sensor (ITR8307) is located on the shell off the gearbox and is pointed to one of the gears inside. That gear is painted half black. The tachometer can pick up 6 pulses per revolution of the wheel.
I-Are-Bot is a robot I’m currently working on for Robot SM 2010 (http://www.robotsm.se).
A bot has to be 100×100[mm] to enter the competition, mine was about 130, therefore I had to built an unconventional bot
Two mini-tower 9G is lifting each wheel pair.
Video of the CAD and prototype
Pirat-Bilen V.2 @ YouTube
The autonomous pirate-car was a huge success at Dreamhack W09, so Benjamin has built a new one. The Pirate-Car V2.
The chassi is from a RC-car, the stearing system has been modified with a servo and it has a better steering-radius. The motor and gearbox is original but it has a reflex-sensor built in the gearbox, the reflex-sensor is aimed to a gear that is painted half black. The sensor can pick up 3 peaks per revolution, these seams to be enough to make the PID-regulator stable.
The autonomous part
The Pirate-Car navigates by it self, it goes around tables, chairs, walls with no problems.
The two front sensors ,left and right, separately calculates how the car should turn. The two turn-values are then subtracted and makes a delta-value that is put out to the steering-servo. This works pretty well, in a corridor the car senses both walls and navigates right between the walls.
The Pirate-Car could sense if it’s stuck in several ways
- Front-center-sensor senses a object close enough
- Front-left and front-right sensors senses a object close enough at the same time
- PID-regulator is delivering a high output that indicates a spinning wheel
If it’s stuck it starts the reversing-procedure, it reverse until the front-sensors feel it’s free or the back-sensors indicates a object.
The main-PCB has a IR-eye hooked up, this eye could pick up commands from IR-remote-controls. Benjamin has written a nice protocol for picking up commands.
Currently two commands could be sent:
- Shut the H-bridge on/off
- Increase/decrease the PID-regulators goal-value
With a Introkit09 we built a remote-control, we used the existing IR-diode to send out IR-commands. But the signal was weak, we then tied to switch to another type (TSAL6400) which were much brighter.
- Make a chaseing-mode, if someone/something tries to catch up the Pirate-Car it goes faster
- When it slows down, brake-lights will glow
- When someone tries to fuck with it, a loud annoying sound and flashing lights will go off
- Following-mode, it tries to follow a person around
The autonomous part