Hydroponic pH and conductivity sensors

i have been running automated hydroponic garden several years. expand garden , input on conductivity sensors.

i have tried multiple circuits , have had problems sensor going out of calibration fast. have come new circuit test shortly.

the frequency needs 1khz+ prevent polarization of ions, , build on 1 electrode on probe.

the ph probe simpler , post schematics shortly.


the circuit follows:

c1 ______________     
         |                |
         |                |
        1nf              |
                       probe
c2____|               |
                          |
                          |
ec _____________|




so if ascii art doesn't right, capacitor connected between pins c1 , c2, , probe connected between c1 , ec.



the pseudo code follows:


1) c1 = high, c2 = low, ec = input
   cap charged vcc
2) c1 = input
3) ec = low
   start discharge
4) time until c1 = low

5) c1 = low, c2 = high, ec = input
   cap charged in reverse
6) c1 = input
7) ec = high
   start discharge
time until c1 = high

9) repeat , average


here function i've put far, if can cut down number of clock cycles on pin changes appreciated.

c1 = pin 7
c2 = pin 6
ec = pin 5



double gettds()
{
  int samples = 16;
 
  int t1 = 0;
  int t2 = 0;

  long count = 0;

  (int i=0;i++;i<samples) {
 
  // c1 high, c2 low, ec input
  // charge cap 
  bitclear(ddrd,5); // ec input
  bitclear(portd,5); // disable pullup
  bitset(portd,7); // c1 high
  bitclear(portd,6); // c2 low
  bitset(ddrd,7); // c1 output
  bitset(ddrd,6); // c2 output
 
  // wait charge ?

  // c1 input, c2 low, ec input
  // set c1 input
  bitclear(ddrd,7); // set c1 input
  bitclear(portd,7); // disable pull up
 
 // c1 input, c2 low, ec low
 // dischage , time
  t1 = 0;
  bitset(ddrd,5); // set ec low , start discharge
  while (bitread(pind,7) == 1)
  {
  t1++;
  }
 
  // c1 = low, c2 high, ec input
  // charge cap in reverse
  bitclear(ddrd,5); // set ec input
  bitclear(portd,7); // c1 low
  bitset(portd,6); // c2 high
 
 // wait charge ?
 
  // c1 input, c2 high, ec input
  // set c1 input
  bitclear(ddrd,7); // set c1 input (already low)
  bitset(portd,5); // set ec / high
 
  // c1 input, c2 high, ec high
  // dischage , time
  t2 = 0;
  bitset(ddrd,5); // set ec output / high
  while (bitread(pind,7) == 0)
  {
  t2++;
  }
   
  count = count + t1 + t2;
 
}


// set pins input
bitclear(ddrd,7);
bitclear(ddrd,6);
bitclear(ddrd,5);
bitclear(dport,7);
bitclear(dport,6);
bitclear(dport,5);


return count / (samples * 2);
 
}

hi, welcome forum.

thanks sharing.

could show picture of probe ? or have website ?
when use reply button (not quick reply field) there additional options in lower-left below text field, used attach photos.

the bitset() , bitclear() compiled the fastest bit set , clear instructions atmega chip. think 2 clock cycles per setting or clearing bit. not possible faster.

code (the sketch) best placed between < code > , < / code > tags. there button (the scroll <> ).

Arduino Forum > Using Arduino > Sensors > Hydroponic pH and conductivity sensors

arduino