-Design Criteria-
Design a combinational logic circuit that will monitor a copier’s three input sensors and activate both an LED and stop the feed motor whenever a paper jam is detected.
- The inputs from the three sensors (A, B, and C) and the output to the motor should be connected to four of the DMS’s general purpose I/O input pins.
- The clear signal should be connected to any of the DMS’s four pushbutton switches.
- The jam signal should be connected to any one of the DMS’s eight LEDs.
-Design Constraints-
- The three inputs (VEX Limit Switches) will require 100K pull down resistors.
- The three inputs (VEX Limit Switches) will require a voltage divider to change the signal voltage from 5V to 3.3V. (180Ω and 330Ω recommended)
- The LED output and Motor output should remain on until the Clear pushbutton is pressed. This will require the pushbutton be latched with a flip-flop.
- The Motor will require a SN754410 Quadruple Half-H Driver or L298 Full Bridge Driver.
- The Motor MUST be powered by an external power supply providing 6V.
- (Batteries or variable power supply)
-Procedure-
-errors-
There was one minimal error in my schematic which caused the circuit to never stop the motor when a jam was detected. The issue was with the clear on my D-FF. The reasoning for this was because I assigned BTN0 to clear the detected jam. BTN0 rests at low and goes high when pressed. Since clear is an active low, the jam was constantly being cleared, causing the output to PIO01 to remain high, and constantly drive the motor. A simple addition of an inverter solved this issue. It is important to not, the interactive constant seen in the image should be placed before the inverter, not after.