CHAPTER 25 ■ LAUNCHING THE LINE-FOLLOWER
Potential Improvements Line-following robot:
Several potentially beneficial changes to the line-following robot have already been mentioned throughout
this book:
- Cover the clear plastic body with something opaque so that ambient light won’t
affect the sensors as much. - Switch to a 6 V rechargeable alkaline battery pack for improved cornering (due to
reduced speed) and longevity. - Use an improved yet completely compatible comparator chip such as the National
Semiconductor LMC6772 to accept sensor voltages in the upper 1.5 V region. - Place an opaque barrier in the middle of the robot between the left set of sensors and
the right set of sensors. This should reduce the light coming from the surface of the
opposite side of the robot. - Select resistors that better match your exact parts. See “Tweaking For Better
Performance” in Chapter 24. - Switch to more efficient motors for longer running time.
- Use modern, smaller surface-mount components to reduce the circuit board to a
quarter of its present size (see Chapter 26 ).
Obviously, you could completely redesign the robot circuit around a smart microcontroller (see Chapter 26 ).
But there are a couple of other enhancements that you can make more simply.
Protecting Against a Reversed Battery
The line-following circuit is fairly robust. It can operate within the entire voltage range of the battery’s
lifespan without the need for a voltage regulation module. The transistors can handle the current to the
motors, even if the motors stall. Flyback diodes protect the transistors from motor spikes. Resistors protect
the circuitry attached to trimpots from the operator dialing extreme values.
There is one common error that can harm the robot’s circuits: inserting the battery the wrong way. If the
9 V battery is touched, however briefly, to the battery snap with the positive terminal and negative terminal
reversed, and the power switch is turned on, the comparator chip could be destroyed.
There is an easy solution to protect against battery reversal. Between the power switch and the positive
power bus, insert a diode (see Figure 25-9). Recall that diodes are one-way valves. As long as the battery
power is going in the correct direction, the diode (D3) will let it pass. If the battery power is reversed, the
diode blocks it.