The following is an electronic schematic and parts list for the items needed to construct an infrared detector for the finish line of a Pinewood Derby racetrack utilizing an external power supply and the parallel port of an IBM compatible computer of at least 486/33Mhz running DOS 3.1 or better. Also included is a narration [...]
The circuit Bargraph Voltage Indicator used IC op-amp two quad voltage comparators to illuminate a series of 4 LEDs indicating volume level.
The op-amp used in this particular circuit is the LM339. It is a popular IC and should be available from many parts stores.
The 1K resistors in the circuit are essential so that [...]
Comparators can be made to perform a basic memory function by wiring them as a ‘SET / RESET’ type of FLIP/FLOP. This type of circuit can be used in unplugable walk around throttles to remember the direction of the train when the controller is disconnected. In the next diagram the comparator will remember which switch [...]
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