I call this robot Explorer :) This can decide its own path using SRF05 ultra sound sensor. Its primary path is going forward, but if it finds obstacle within 20cm distance, it checks right and left. By comparing the distance of the obstacles in both right and left (if present) it decides its path. A 16x2 LCD has been used to display the information about what the robot is doing. The brain of this robot is an Arduino Mega 2560, I know same thing could be done using the UNO or just the ATmega8. But just tried with the Mega :D To tell about the sensor, SRF05 is one of the best ultra sound sensors I've used so far, I meant comparing to SRF04 or whatever. This is a complete Arduino project, compiler was Arduino as well.
Yes it has an independant Vin and supports from 7V to 12V, it has integrated voltage regulator on board and regulates the voltage to 5V. So you can use 9V battries. Or if you want to supply just 5V, you need to use the USB port of the Mega, in that case you have to use external voltage regulator, I used 7805A and its common and available.
It has 2 gear motors and a servo which drain a lot of power, this is why I made a different circuit to supply power to these motors. Supplying power to these things form Arduino may damage the Arduino, even if it works, they’ll get not enough power. So it is better to supply power from a different source. I always prefer different power sources for Arduino/MCU and the other components, ie. the motors or sensors
I used a 9V source for the Arduino mega and the other source to power the Motors, I’ve attached a comparable circuit design with it for your convenience
I haven’t shown capacitors, but its good to use capacitors. And to supply power to the motors, I’ve used 2 9V battries in parallel. Please check the design in the top.
But I’ve tested with my hand drill, it works fine