Changing designated Pot Values to read 0?

Projects Programming
1

Howdy, not quite sure how to ask this. What I am trying to achieve is like constrain but a little different. I would like to set a value, say 10, where any value read that is below 10 is changed to 0. I am getting some values of 2 or 3 when the potentiometer is moved quickly to the furthest position to off.

I want to ensure that anything below that delta of 10 is sent out as a 0 so it always sends an off value. I believe the delay function that I need to use may be adding to the problem if it's physically reading a 0 from the pot while inside the delay. (?)

Serial info goes to an XBee. The receiving XBee serial info is processed and a PWM LED will ghost if the las5t value seen is a 2 or 3 etc. along with a DAC. The sketch shows the use of constrain but the end result is still the same.
Thanks in advance for any simple ideas.

0 = 0
1 = 0
2 = 0
3 = 0
4 = 0 etc
11= 11
12 = 12
13 = 13 etc

#include <SoftwareSerial.h>

SoftwareSerial mySerial(1, 0); // RX, TX
const int potPin = A1;  
//Variables:
int potVal = 0; 
int potValPrev = 0;
  
void setup() {                              
  mySerial.begin(38400); 
}
void loop() {    
    //Read the analog value from pot and store it to "value" variable
    potVal = analogRead(potPin);
    //Map the analog value to pwm value
    potVal = constrain(potVal, 80, 1023);   //?????????   80, 1023 for 802.
    potVal = map (potVal, 80, 1023, 0, 255);          //  80, 1023 for 802.
                                           
    if (abs(potVal - potValPrev) > 2)     
                                       
    if (potVal != potValPrev) {             
      mySerial.print('<');
      mySerial.print(potVal);
      mySerial.println('>');
      potValPrev = potVal;
      mySerial.flush(); 
      delay (6);             
    }
}
2

If I understand correctly what you're asking for, how about:

    potVal = analogRead(potPin);
    if (potVal < 10) {
        potVal = 0;
    }
    potVal = map(potVal, 0, 1023, 0, 255);
3

While it's inside the delay it's not reading anything from the pot, it's not doing anything at all, which is what delay does. Learn to code without using delay.

4

Without knowing exactly what you are trying to achieve I see some concerns.
1: Is the "zero" value ALWAYS less than 10? If so you can use

if (potVal < 10) {
        potVal = 0;
    }

However do you then want to represent 11 as 11 or as +1?
How about

potVal -=10; 
if (potVal < 0) {
        potVal = 0;
    }

The extremes of a pot track will not behave linearly.

Also depending on the quality of your pot you may wish to allow for more noise here

if (abs(potVal - potValPrev) > 2)  //by making the "magic number"  (2)  bigger.
5

Yes, thank you. I am trying it now. I have raised the delta number value to 16 and it's gotten better. I need to keep the mapping in mind as well. I had convinced myself that it was going to be much more complex math.

6

Thank you. I am using millis on the receiving end of this so I am familiar with blink without delay. This is the entire code for this ATtiny 85 chip. There are no other functions being delayed by using this so I kind of just concentrated on the performance of the serial information being broadcast without overloading the serial buffer in the XBee's by adjusting the delay time.
I understand the potVal - potValPrev > 2 also reduces the number of integers being used.

7

Thanks for looking. I think I'm ok with having the resolution of this small area of the wiper being ignored. I will look at your second option.

The pots I use are quite good and I don't have a problem with any jitter beyond my current "magic number." I have used a higher number but I don't like how it feels when so many values are skipped while moving the pot.

8

Perhaps better to use a simple digital filter. I've a bit about it here, very simple code and gives a nice smooth response.

9

@johnerrington nice article.

Not gonna say how long it took me to figure out what

a simple CR filter

is. :expressionless:

a7