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Troubleshooting why Arduino logical operators doesn't compute

colporteur

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How would you write the expression to test sensors Departure (A or B) HIGH AND Arrival (A or B) HIGH?

The first else if statement shown below doesn't work. Departure A OR Departure B HIgh AND Arrival A OR Arrival B High. The OR doesn't work. Only when both Departure A AND B are HIGH the serial print. The same applies to the third else if statement both Departure A and B have to be low for the statement to function. What am I coding wrong for the OR?

      if ((digitalRead(s1DeparturePinA) == LOW || digitalRead(s1DeparturePinB) == LOW) &&
          (digitalRead(s1ArrivalPinA) == HIGH || digitalRead(s1ArrivalPinB) == HIGH))
        {
         Serial.println(F("Train on siding 1 status DEPARTURE")); 
         delay(1);
        }
      else if ((digitalRead(s1DeparturePinA) == HIGH || digitalRead(s1DeparturePinB) == HIGH)&&
               (digitalRead(s1ArrivalPinA) == HIGH || digitalRead(s1ArrivalPinB) == HIGH))
        {
          Serial.println(F("Train on siding 1 status IN TRANSIT"));
          delay(1);
        }
      else if ((digitalRead(s1DeparturePinA) == HIGH || digitalRead(s1DeparturePinB) == HIGH) &&
               (digitalRead(s1ArrivalPinA) == LOW || digitalRead(s1ArrivalPinB) == LOW))
        {
          Serial.println(F("Train on siding 1 status ARRIVAL"));
          delay(1);
          s1ArrivalDetect = LOW;
        }
      else if ((digitalRead(s1DeparturePinA) == LOW || digitalRead(s1DeparturePinB) == LOW) && 
               (digitalRead(s1ArrivalPinA) == LOW || digitalRead(s1ArrivalPinB) == LOW) &&
                s1ArrivalDetect == LOW)
        {
          Serial.println(F("Train on siding 1 status STOP"));
          delay(1);       
        trainOneOut = LOW; //train selection flip_flop L=train on siding 2
        s1ArrivalDetect = HIGH;
        digitalWrite(l1_TurnoutL, LOW);  //unset departure and arrival turnouts for train1
        digitalWrite(s1_Power, LOW);        //unset power on for train1
        digitalWrite(l1_TurnoutR, HIGH);  //set departure and arrival turnouts for train2
        digitalWrite(s2_Power, HIGH);        //set power on for train2
        }
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  • /members/colporteur ok I use a lot of switches and have found the cheapest and easiest is to use a Schmitt Trigger (.64$ @digikey)/6 = 0.166$ for each section with an R/C filter. take a look at this blog of mine.

    imageimageThis is cheaper than the 555 solution, as for six debouncers but then you need a 555 (0.40$@digikey) * 2 = 0.80$) for your project. This gets pricey as they will require 2x resistors & capacitors, and a lot more soldering.

    Normally I put the R/C networks on an IC header if it is a 16 pin header I can put 4 networks on it. and this is on a Wire-Wrap socket. 

    image

  • in reply to phoenixcomm

    It could use some investigation on my part, this schmitt trigger. I'm getting false starts on some animations and would like to find a solution. Got a part number? Looks like you designed a board to accommodate it.

  • in reply to colporteur

    The hardware debouncing will certainly do the job.
    If your Arduino isn't doing a lot, there is also software debouncing. I prefer hardware solutions, like the one  suggests.
    But if your scenario is repeatable (I think it is, because it is a train doing the same thing over and over, at a predictable speed) the software debouncing will do.
    I checked out a number of debounce examples for Arduino before and blogged about it here (many years ago). I'm having troubles to find it back.

  • in reply to colporteur

    There are some Arduino libraries for software debouncing but I haven’t used them. The method I use is described in this blog and seems widely accepted. My code doesn’t use the Arduino IDE but it could be adapted. See the links in the blog for a better explanation and some other methods. 

    This TI documenthas part numbers and how to calculate values for a Schmitt trigger. 

  • in reply to fmilburn

    Thanks for the input. I had a read and tried to pencil out an understanding. Got stuck trying to understand but had no one to ask a question of. Back to square one.

    I'm thinking in my case the sensor is not a button. Can I do without the button debounce?

  • in reply to colporteur

    NOPE! GOTA Have Debounce.  so you have 4 switches, that are open or closed. that's eight states. so let's cut it in half as we only care about the Active States. first I would take a 4 input or-gate and tie it to each switch and to 4 Arduino inputs. take the output of the or-gate go through the Schmitt trigger to an ISR. Now when the ISR is triggered you read the 4 inputs to find the active one.

    KISS Principle (Keep It Simple Stupid) This applies to everybody. 

    OPS! you need two ISRs one for each track. and I would not use the quad input or gate. use 2 2-input or gates. 

  • in reply to colporteur

    If you have an oscilloscope you can watch the switch and see if it is bouncing. I would guess that it does. What the software I linked does is check to make sure it doesn’t change state (or bounce as they say) faster than a human can push and let go of a button. Your switch may be chattering for quite some time. If you don’t have an oscilloscope maybe set the Arduino to print in a simple loop for one section of track as fast as it can and look for a period where it changes output from 0 to 1 several times in a row when the train moves. If so, how long does it last?

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  • in reply to colporteur

    If you have an oscilloscope you can watch the switch and see if it is bouncing. I would guess that it does. What the software I linked does is check to make sure it doesn’t change state (or bounce as they say) faster than a human can push and let go of a button. Your switch may be chattering for quite some time. If you don’t have an oscilloscope maybe set the Arduino to print in a simple loop for one section of track as fast as it can and look for a period where it changes output from 0 to 1 several times in a row when the train moves. If so, how long does it last?

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