Digital Voltmeter (0-99%)

Description
Re-maps a number from one range to another. That is, a value of fromLow would get mapped to toLow, a value of fromHigh to toHigh, values in-between to values in-between, etc.
Does not constrain values to within the range, because out-of-range values are sometimes intended and useful. The constrain() function may be used either before or after this function, if limits to the ranges are desired.
Note that the "lower bounds" of either range may be larger or smaller than the "upper bounds" so the map() function may be used to reverse a range of numbers, for example
y = map(x, 1, 50, 50, 1);
The function also handles negative numbers well, so that this example
y = map(x, 1, 50, 50, -100);
is also valid and works well.

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Example
/* Map an analog value  (0 to 99) from 9 volts to 12.6 */
void setup() {}

void loop()
{
  int val = analogRead(0);
  val = map(val, 730, 1023, 0, 99);
  Serial.write(val);
}

be80be said:

The ghosting is because your not blanking the display. See you write to the shiftreg then turn on the display. Your code has them on when you do a update.

Like this

Code:

digitalWrite (seg1, low); digitalWrite(seg2,low):
shiftOut //data here
digitalWrite (segX,High); //desplay your data here
digitalWrite (seg1, low); digitalWrite(seg2,low)://turn them off to load new data
shiftOut // new data here
digitalWrite (segX,High);//desplay your data here

Click to expand...