DIY PAR meter, Yeah you heard me

[O2surplus]

I think I must have done something right. After making a few mods to Mistergreen's code to match the lcd circuit that my controller uses, I uploaded the code and SHAZZAAAAM! It works-



Here's the modified code-

#include <LiquidCrystal.h> // modified by O2surplus

float average = 0;
float output = 0;
float factor = 1.52;
unsigned long time;
int counter = 0;
// create the LCD
LiquidCrystal lcd(8, 7, 5, 4, 16, 2);
// set up backlight
int bkl = 6; // backlight pin

void setup() {
  time = millis();
    // set up the LCD's number of rows and columns: 
  lcd.begin(16, 2);
  // Print a message to the LCD.
  lcd.print("2noodles PAR");
  pinMode(bkl, OUTPUT);
  digitalWrite(bkl, HIGH);
  
}

void loop() {
  int sensorValue = analogRead(0);
  average += sensorValue;
  counter++;

  //every second or 1000 millis
  if(millis() > time+1000) {
     //corrections to fit par
   average = average/counter;
   
   if(average <= 560) {
     factor = 1.55;
   } else {
     factor = 1.36;
   }
   //corrects for high PAR
   output = average * factor;
   
    // set the cursor to column 0, line 1
    // (note: line 1 is the second row, since counting begins with 0):
    lcd.setCursor(0, 1);
    // print the number of seconds since reset:
    lcd.print(output);
  
    //reset timer & counter to get ready for the next second.
    time = millis();
    counter = 0;
    average = 0;
  }
}

Next will be to order some boards, put a couple together, and send'em to Mistergreen for evaluation and testing.

[HD Blazingwolf]

when this gets done. i will buy one to support the hobby. i can't do math, or coding, or decide whci hway to wire and code a microprocessor. i understand these principles well, just don't have the knack for actually making a system. but i can take anythign apart and replicate anything done efficiently which includes prewritten code, and fully assembled systems

[mistergreen]

I'll make sure it's calibrated to actual PAR numbers and then will post it on the S&S probably. It'll probably be $40 - $50 over-all... Not sure about encasing this in a project box or not for the sake of cost and assembly time. Maybe we'll leave that up to you guys.

[O2surplus]

Mistergreen- Can you think of anything, component wise, that should be added to the PCB? I was wondering if it would be prudent, to add another 1kohm pot inline with the 27kohm resistor, to allow for fine tuning of the signal coming from the photo diode? It's a simple matter to make any additions now, prior to the board production run.

[mistergreen]

Originally Posted by O2surplus

Mistergreen- Can you think of anything, component wise, that should be added to the PCB? I was wondering if it would be prudent, to add another 1kohm pot inline with the 27kohm resistor, to allow for fine tuning of the signal coming from the photo diode? It's a simple matter to make any additions now, prior to the board production run.

That's actually a pretty good idea. I was going to adjust the code for fine tuning

[aaronbrown]

i want one when you get them up and operational just let me know the price and where to send it

[O2surplus]

Ok - I added a 5kohm pot in line with the resistor. I dropped the value of the resistor to 24.9k ohms so that with the additional resistance provided by the pot, total circuit resistance can be varied from the 27k Ohm target + or - 2.5k. This should allow for an increased PAR sensor calibration range. Here's the latest PCB. I'll send the files out for production and have some boards by next weekend.

[Chlorophile]

Originally Posted by O2surplus

Mistergreen- Can you think of anything, component wise, that should be added to the PCB? I was wondering if it would be prudent, to add another 1kohm pot inline with the 27kohm resistor, to allow for fine tuning of the signal coming from the photo diode? It's a simple matter to make any additions now, prior to the board production run.

I have no idea what that might do, but I am wondering if that is something that maybe the end user shouldn't be able to tweak?
What would the effect be of adjusting the potentiometer?
It seems it would be nice for us all to have identical equipment so our readings are comparable.
Again I don't know what the heck it does, but I am wondering.

[mistergreen]

When you build applications, you try to be flexible so not to paint yourself into a corner. Things are rarely fixed so a little calibration is needed but the end product should be standardized.

For instance, a 27k resistor isn't really 27k. It can vary from 26.6k to 27.2k or something like that. That affects the read out. So, having a pot, I can calibrate the read out to match actual par readings.

I have an apogee par sensor.

[O2surplus]

Ok everyone- I sent the PCB design files to SeeedStudio this morning. If everything goes smoothly, I should have 10 of the Pcb's in my hands in about 9 days. I'll then solder some of them up and send them out to Mistergreen for testing.

Mistergreen- Please send me a PM with your mailing address, when you have time.

[audioaficionado]

Subscribed.

It will be nice for a DIY alternative to the $$$ least expensive units I've looked at.

[mahko]

Same. Subscribed. This looks really cool.

[mistergreen]

Let's give this a name. How about "Close enough PAR".
O2Surplus, If you're going to upload the binary, can you change the 2noodles to that? It's 16 characters exactly

[O2surplus]

Originally Posted by mistergreen

Let's give this a name. How about "Close enough PAR".
O2Surplus, If you're going to upload the binary, can you change the 2noodles to that? It's 16 characters exactly

I can do that. I was going to name mine " H&H PAR" which is short hand for "Horse shoes & Hand Grenades". since you only have to be "close enough" with either to win .

[tentacles]

How does a person get a place on the waiting list for these?