By default at power-up, the circuit is in coast mode. To brake, set IN A to 0 V, IN B to 0 V, and Q5 to 5 V. To spin clockwise, set IN A to 5 V, IN B to 0 V, and Q5 to 5 V. To spin counterclockwise, set IN A to 0 V, IN B to 5 V, and Q5 to 5 V. At any time you can return to coast by applying 0 V to Q5. Or, you can apply pulses of 0 V/5 V/0 V/5 V (and so on) to control the speed. The more time spent at 5 V, the faster the motor will spin. Whenever you change modes, if you set Q5 to 0 V before making changes to IN A and IN B (and then set Q5 back to 5 V or pulsing) there will be no shoot-through.

The Basic Stamp > interprets instructions in real-time, essentially running a virtual machine on the PIC. This means that it is much slower

The Stamp implements a complete solution on a single PCB. In comparison, a bare PIC requires a separate power regulator and substantial decoupling on its output.

the Cricket's green LED light goes on while the Cricket is executing commands.

You can "launch" a procedure directly from the Cricket by pressing the white button on the Cricket.

You can send information from the Motor/Sensor Cricket back to the computer using the send instruction.

These above rules handle all of the commands and expressions of the iLogo language except for the DoUnlessCommand. This command will execute a list of commands unless a boolean condition is met. If so, control is switched to a new list of commands for handling the exception condition.

Each stage of the compiler is designed using the Visitor pattern described in the book Design Pattern by Eric Gamma, et al. This pattern allows tree traversers to be created as seperated objects, instead of doing all traversals as methods of the nodes of the tree

We decided to use the JavaCC/JJTree tools created by Sun for generating a custom parser for our iLogo language written in Java.

The language must have primitives which allow the user of the language to write programs which easily transfer control based upon outside stimuli, in this case sensors on the truck.

An LM18293 push-pull motor driver connects the programmable counter array (PCA) of the 8051 to the truck's motors.

We took the Berkeley Logo language design as our base and then added a primitive for reading sensor and an exception-based control structure.

The '240 is often called "the bicore chip," because we can take advantage of the 240's inverters to turn a single 74*240 into a bicore

The '240 also has tri-state outputs, so an enable line can be used to turn its outputs on and off simply (good for adding reversing capability to a 'bot).

any *cores built with a 74*04 will require additional logic "downstream" to amplify the current to levels sufficient to drive a moto

Schmitt triggers can't easily be used in suspended bicore implementations

use its buffers as little current amplifiers

it is usable for either grounded or suspended bicore designs (but better for suspended)

74HC/HCTxx non-buffers (74HC14 or 74HC04) draw about half of the current consumption, and have about half the drive current compared to HC / HCT buffer chips (74HC240 or 74HC245). Non-buffer chips are thus better for oscillators, say Nv and Nu applications; they are not suited for use in driving motors.

74AC is best suited for motor driver applications with all inputs driven rail to rail.

The '245 is an octal buffer chip, and so has 8 channels of buffering power available for our misuse. This chip was designed for data transmission uses, but we'll misuse it as a motor driver chip

The '244 provides us with 8 (thus the "octal") buffers, enableable in banks of 4. This is a very useful chip for amplifying small currents

it can drive up to 4 motors in 2 directions each, or you can "buddy up" inputs and outputs to drive fewer motors at higher current

it can drive up to 4 motors in 2 directions each, or you can "buddy up" inputs and outputs to drive fewer motors at higher current

If you can't find 1381s locally, you might have better luck finding its European cousin, the TC-54 -- for details on it

Note that if you need more than about 200 mA per motor, you'll need to use an H-bridge, or some similar motor driver

The ideal BEAM circuit would use a low (2V-3V) voltage core and sensors combined with level shifting high (5-6V) volt motor drivers to maximize efficiency.

74ACxxx used in typical BEAM applications uses 4x more supply current than does 74HC/HCTxxx.

The Gate acts as an antenna, so leave it unconnected.

The 1-meg resistor helps protect the FET from being harmed by any accidental sparks to its Gate lead. The circuit will work fine without this resistor. Just don't intentionally "zap" the Gate wire with a charged object or your charged finger.

To test the circuit, charge up a pen or a comb on your hair, then wave it close to the little "antenna" wire. The LED should go dark. When you remove the electrified pen or comb, the LED should light up again.

If you suspect that humidity is very high, test this by rubbing a balloon or a plastic object upon your arm. If the balloon does not attract your arm hairs, humidity is too high.

This FET sensor is not an ideal educational device because it responds differently to positive than to negative.

negative objects turn the LED off, it lights again when removed. positive objects make the LED bright, then dark when removed.

Obtain a small capacitor with a value below 100 picofarads. Connect it between the FET gate lead and one of the other FET leads (doesn't matter which one.) This greatly reduces the sensitivity of the device

Now make the circuit MORE sensitive. Obtain an alligator clip-lead, and connect it to the Gate lead of the FET. Let it hang loose without touching anything. You'll find that this has vastly increased the sensitivity of your FET circuit.