This a simple robot built based on PIC microcontroller, this single robot has multi functions to do some works.
The robot has the following objectives :
1. Follow a black line track with sharp turns
2. Ability to maneuver through breaks in the line
3. Detect obstacles and manuever around them
4. Identify colors to be able to locate green and aluminum victims.
Original robot tutorial here
I’ve once use L298N for my line follower robot. This is cheap and able to control motor which need quite electric current to run. I recommend this driver IC for your robot… 
Download the schematics an tutorial here
Robot arm at this time has been used in major industries. This robot is used to make production more quickly and accurately. But you know that to design a robot arm requires an accurate calculation?
Yes, the robot arm is one of the robots that have a working principle similar to the human arm movement. To design a robot arm is very complex because it requires the cooperation of appropriate motor movement. You should also consider the type and torque of motor and also determine where your motor will attach.
Sound activation also knows as tone detector is one of sensing system that usually used for robot start up activation. When some frequency have received by microphone in this circuit, then the robot will start to move.
I’ve collected some schematic diagrams of sound activation as follow:
Sound Activation schematic 1
Sound Activation schematic 2
This can be used as reference