Simple Robot That Drives Forward and Back

Posted on Feb 7, 2014

The Flip-Flop Robot drives forward until it hits an obstacle, and then reverses until it hits another obstacle. This back-and-forth process continues indefinitely. By limiting the functionality to this very rudimentary behavior, it can be generated from an off-the-shelf chip instead of requiring a fancy microcontroller. Thus, this is a good robot

Simple Robot That Drives Forward and Back
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project for beginners. Avid fans of Robot Room will recognize the 7474 chip from the Laser Control project. This chip has two independent one-bit memory cells. You can read all of the operational details and see a movie in that article. Briefly, the 7474 has a set (pin 10) and a clear (pin 13). The rear bumper switches are connected to the clear pin. When the rear bumper is pressed, the chip`s output (pin 9) is cleared (0V). This output connects to the motor driver chip and makes the robot drive forward. The function of the 7474 is to remember the output state even after the bumper is released. The front bumper switches are connected to the set pin. When the front bumper is pressed, the chip`s output (pin 9) is set (5V), rather than clear (0V). This commands the motor driver chip to drive the motor backwards. The 7474 remembers this new output. An oddity of the 7474 chip is that the set and clear pins are activated by a low (GND 0V) signal. Therefore, resistors R4 and R5 provide a high (5V) signal by default, so that the chip will not normally think that the set or clear pins are being activated. The bumper switches connect the appropriate pin to 0V when pressed, to activate the set or clear feature. The power switch (SW1) connects the circuit to the battery when turned on. The diode (D1) prevents electricity from flowing in the wrong direction if the batteries are inserted backwards. Current is only allowed to flow in the...

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