Copy Jam Detector
If you have ever used a copier, it is inevitable that you’ve
encountered a paper jam. The flashing lights and irritating buzzers are enough to drive you
crazy. As annoying as these are,how else would we be able to know that a paper jam has
occurred?
encountered a paper jam. The flashing lights and irritating buzzers are enough to drive you
crazy. As annoying as these are,how else would we be able to know that a paper jam has
occurred?
Problem StatementDesign and build a copy jam detector circuit that will alert you whenever you have a paper jam.
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Constraints-Use progammable logic instead of traditional discrete logic
-Build it on a Digital Logic Board -Use VEX® Paper Jam Detector Kit |
DocumentationCopy Jam Detector Truth Table:
Copy Jam Detector circuit design using programmable logic (PLD):
The VEX® Paper Jam Detector Kit wired up to the Digital Logic Board:
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CalculationsLogic Expression for the Copy Jam Detector using the K-Map technique:
Asynchronous Inputs:
Basic layout of how the VEX® Paper Jam Detector Kit will be wired on the Digital Logic Board:
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Final Design
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The Copy Jam Detector final design was derived using traditional discrete logic, and then converting it into a programmable logic design so that it can be physically displayed, on the digital logic board, with the aid of the VEX® Paper Jam Detector Kit. The logic expression was derived from the truth table created from the following set of constraints: “As the paper passes through a copy machine, three sensors monitor its path. The sensors consist of a normally open SPST switch using only the black and white wires. When a paper closes the switch, the output is a logic one (1). When the switch is not closed (i.e., there is no paper), the output is a logic zero (0). Under normal operations paper will pass through the sensors such that adjacent sensors will not simultaneously detect paper. If they detect paper, this indicates that a paper jam has occurred” (Project 2.5.3V Copy Jam Detector Design). In the programmable logic design, instead of SPDT switches you will use GPIO’s, and the D Flip-Flop’s data and preset will be wired to a Digital High constant. You will use a button (BTN0), attached to an inverter, to reset the Copy Jam Detector.
The circuit is designed to have two lights lit up whenever there is a paper jam, but in this case, LED0 will turn off when the paper jam is fixed, and LED1 will stay on until the system is reset (BTN0). The way this works is that whenever LED0 is lit up, that signal is sent to the flip-flop (CLK), which will check data (D). Before it can go and check data, it has to go through preset (PR) and clear (CLR), which will determine whether the clock can check data, or if it will be overwritten by preset or clear (See Asynchronous Inputs). CLR is wired up to the BTN0 through an inverter, so that whenever BTN0 is off, the signal to CLR is a 1. Both the D and PR are wired to a digital high constant making them both 1’s. Since PR, CLR, and D are all 1’s, Q is a 1, which will make LED1 light up. Know the thing about this is that it won’t matter if you have fixed the paper jam, because in order for anything to be altered in the flip-flop (including LED1) the signal from CLK will have to be a one since CLK has a positive edge trigger. Even when the CLK is on, the signal will still be the same, and the light will stay on, indicating that the system is still not in reset. So to change this, when you press BTN0, the inverter sends the input as a 0 to CLR, and when PR is a 1, and CLR 0, no matter what D is, Q will be a 0, which will reset the system. |
Reflection
The only challenge, throughout the whole project, was the whole project itself. This was a true learning experience,
which took hours, upon hours of trial and error, in order for me to get to where I am in today. There were many
challenges to overcome in this project. Converting from discrete logic into programmable logic was not hard. The challenge was getting the flip-flop to do what I wanted it to do. In the beginning I didn’t really know what I wanted to happen, once I got a paper
jam in the system. Once I obtained the truth table about how flip-flops work, and how it has to go through preset
and clear, before the clock can check what data is up to, was all fundamental in understanding how this design was going to be set up. Another challenge was in wiring the VEX®Paper Jam Detector Kit onto the digital logic board. We used
GPIO’s instead of switches, so that the VEX® Paper Jam Detector Kit could serve as our switches, by wiring it onto the board itself.
This board works basically like the breadboard, except you have to add the resistors in the right place, you need to know that the red wire on the switches don’t to do anything, that the black wire is for 1 and the white for 0,
and of course that the wiring has power. I can’t wait until we get our next project that deals with using the
digital logic boards, because I think I will have a better time using it than this time, but I can take a real learning experience from this.
which took hours, upon hours of trial and error, in order for me to get to where I am in today. There were many
challenges to overcome in this project. Converting from discrete logic into programmable logic was not hard. The challenge was getting the flip-flop to do what I wanted it to do. In the beginning I didn’t really know what I wanted to happen, once I got a paper
jam in the system. Once I obtained the truth table about how flip-flops work, and how it has to go through preset
and clear, before the clock can check what data is up to, was all fundamental in understanding how this design was going to be set up. Another challenge was in wiring the VEX®Paper Jam Detector Kit onto the digital logic board. We used
GPIO’s instead of switches, so that the VEX® Paper Jam Detector Kit could serve as our switches, by wiring it onto the board itself.
This board works basically like the breadboard, except you have to add the resistors in the right place, you need to know that the red wire on the switches don’t to do anything, that the black wire is for 1 and the white for 0,
and of course that the wiring has power. I can’t wait until we get our next project that deals with using the
digital logic boards, because I think I will have a better time using it than this time, but I can take a real learning experience from this.