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1  Using Arduino / Sensors / Re: Has anyone solved the MAC 31855 high temperature instability problem. on: Today at 10:17:34 am
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Does the high temperature cause bubbles?

The temperature probe is inserted through  the side of the kiln wall. It is not in contact with the ceramic pieces so it should be measuring the air temperature inside the kiln.

I ran another test yesterday by just heating the probe tip with a propane torch. The prob tip got up to 1900F and showed no jitter. I held it at this temperature for several minutes with no erratic readings. So I think that there is some noise happening with the electric kiln.  The elements should be giving a simple resistive load so I am not sure what  might cause the noise to start happening at higher temperatures, but maybe it is coming in through the line rather than the probe.

I'll put an O-scope on it next time I make a run with the kiln.
2  Community / Exhibition / Gallery / Re: Arduino controlled battery charger on: September 14, 2014, 07:10:00 pm
PRETTY COOL... looking forward to the code you used. I am thinking of doing similar to this but with a solar charger
3  Using Arduino / Sensors / Re: Has anyone solved the MAC 31855 high temperature instability problem. on: September 14, 2014, 03:20:57 pm
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Q: Can you check with a sensitive voltmeter if the voltage over the sensor is stable?

Q: can it be that the temperature/heat is not equally distributed?

I have watched the max readings jump all over the place, while at the same time not change more than 0.1 ma on a voltmeter. I even tried two voltmeters to make sure.
As I said before, the AD 595 is stable under the same conditions.

I am going to try and hook it up to an oscilloscope next time and see if I can see anything. 

The heat is evenly distributed. The kiln has a tremendous thermal sink compared to the thermocouple.

This has got to be a noise issue somewhere, but why does it only happen at high temps???

Thanks again Rob... I'll have a try with your library.
4  Using Arduino / Sensors / Re: Has anyone solved the MAC 31855 high temperature instability problem. on: September 14, 2014, 11:17:35 am
yeah Rob... somewhat sloppy coding. I started out with just one if statement and just kept adding on

Can't remember where I got the library. included is a zip of the library I am using, in case any one else is interested. It works fine in most cases.
5  Using Arduino / Sensors / Re: Has anyone solved the MAC 31855 high temperature instability problem. on: September 13, 2014, 11:11:05 am
Yes I mean MAX 31855

I am using a k type thermocouple.

here is the code
Code:
#include <MAX31855.h>

float tempOut = 0;
int command = 0;
int value;
// Adruino 1.0 pre-defines these variables
//int SCk = 13;
//int MISO = 12;//SO
//int SS = 11;//CS

// Setup the variables we are going to use.
double tempTC, tempCJC;
bool faultOpen, faultShortGND, faultShortVCC, x;
bool temp_unit = 0; // 0 = Celsius, 1 = Fahrenheit
//temp(SCk,CS,SO)
MAX31855 temp(11, 12, 13);

void setup() {
 
  pinMode(2, OUTPUT);      // Test Com Reset issue 
  pinMode(3, OUTPUT);
  pinMode(9, OUTPUT);
  pinMode (10,OUTPUT);
  digitalWrite(10, HIGH);

  Serial.begin(9600);

}

void Average10() { // average 10 readings
 
  float Ave;
  int AveCt ;
  AveCt =0;
  Ave = 0;
  delay(50);
  do {
 
      temp.readMAX31855(&tempTC, &tempCJC, &faultOpen, &faultShortGND, &faultShortVCC, temp_unit);
      Ave = Ave +  tempTC ; // tempTC ;
      AveCt = AveCt + 1;
      delay(10);
     } while  (AveCt < 10 ) ;
 
    tempOut = (Ave/10);
 }

void loop() {
   if ( analogRead(0)> 1021) {          // it's too high turn it off
          digitalWrite(2,LOW);
      }
     value = 0;
     Serial.flush();
     if (Serial.available()) {      // Look for char in serial que and process if found
      command = Serial.read();
      if (command == 84 ) { // If command = "T" turn it on (unless to high)
          digitalWrite(2,HIGH);
         // delay (500); // keep it on for at least half a sec to prevent bounce
      }
      if (command == 67) {          // If command = "C" turn it off
          digitalWrite(2,LOW);
         // delay(500); // keep it off for at least half a second to prevent bounce
      }
      if (command==68){                 //if command ="D" sound tone
        tone(9,220);
      }
      if (command==69){                 //if command ="E" end tone
        noTone(9);
      }
          command = 0;                 // reset command
   }
    delay(50);
    Average10(); // take averaged sample
    delay(50);
    Serial.flush();
 
    Serial.print("@- ");
    Serial.print(tempOut);       // output to computer USB port
    Serial.println(" -Tmp ");
 
 }
6  Using Arduino / Sensors / Has anyone solved the MAC 31855 high temperature instability problem. on: September 10, 2014, 08:36:25 pm
I set up a kiln controller some years back using a AD 595 chip. It worked well and gave consistent results form 25F to around 2150F. The only problem was the output was above 5 volts at the high end so I had to use an external 12 volt source and reduce the final signal down to the 5V limit of the Arduino A/D.

So I tried the  MAC 31855. All went well till about 1400-1600F then it started throwing wild readings. I tried two different boards different shields, same thing... erratic readings from around 1400F. I did all the usual stuff with caps and twisted pair. Nothing works.

Searching the web, I discovered at least three other people with the same problem, but it didn't look like it got resolved.

The thing is that the readings seem rock solid till some point around 1400F, then the immediately go crazy. Shifting back to the AD 595 shows on instability at all. ???
7  Community / Bar Sport / Re: Idiotic Table - A periodic table for idiots on: June 09, 2014, 08:39:11 pm
The very worse out here is the dreaded dormant rockadillo
8  Using Arduino / Project Guidance / Re: How to measure the frequency of a AC sine wave signal? on: October 28, 2013, 02:00:51 pm
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Haw! That's cute as hell.
9  Using Arduino / Installation & Troubleshooting / Re: pc doesn't recognize arduino as arduino on: October 03, 2013, 06:24:20 pm
And don't upgrade to windows 8 !
10  Community / Bar Sport / Re: Little physics brain teaser on: August 30, 2013, 07:18:27 pm
It doesn't seem to follow Ohm's law.
11  Using Arduino / General Electronics / Re: A question about solar panels on: August 06, 2013, 10:52:20 am
There are numerous tutorials on how to interface battery storage with solar panels. Most of the weather stations you see advertized have this setup.

 Some of them are pretty cheap and even include data storage, wireless connection and processing software. Might be better to just throw some money at it if you are serious about gathering weather data.

Google is your best friend in learning electronics.
12  Topics / Education and Teaching / Re: How well US students prepare for science and engineering on: July 26, 2013, 01:40:47 pm
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I think that the bottom line is that it is fine using aids to calculation but you need to be able to tell if the result is wrong for what ever reason, be it malfunction or user error.

And it doesn't matter if that aid is log tables, slide rule or electronic calculator.

When I was a G.A. in grad school I had a prof who insisted we we sum up test scores in our head, when we graded papers. Since the numbers were never more than two digits, it was pretty easy. However what I do now is take lots and lots of percentage compositions. like  1209.4/5321.8
I really can't see using long division to get the answer.
13  Topics / Education and Teaching / Re: How well US students prepare for science and engineering on: July 22, 2013, 11:03:15 am
I agree with you liudr Scientists and engineers... and pretty much every one else need to be familiar with basic math. The point is that the rote memorization of times tables and the ability to do long division on a piece of paper is no longer as important as it once was.

I agree, it seems like there is far less emphasis on science and math in schools. Back in the 1960's when I was in school, even the local Junior collages were offering four full semesters of calculus, chemistry and physics. Now this is condensed into one or two semester overviews. Also the inflated grad system was not in place. If you got and A or B in these courses , you deserved it.
14  Topics / Education and Teaching / Re: How well US students prepare for science and engineering on: July 21, 2013, 08:04:05 pm
I can still add, subtract,multiply, divide but a hell of a lot slower than I used to. I also used to use Log tables and a slide rule. The sad (or happy) fact is that I no longer have to know any of these things. Calculators and computers have made these manual processes obsolete. And how many engineers won't tip their hats to spell checkers. Now I can write a an intelligent looking document without spending half my time in a dictionary!

I'm thinking that this will only get worse with time. The question is; does everybody really need to know how to do simple math by hand? It's fine to know the underlying theory but how many real world situations do you run into where you can't grab your nearest electronic crutch and type in the numbers?

When I was in high school. You were not allowed to use anything but a pencil on any kind of test, now most places allow calculators, and why not. This is the twenty first century. The paradigm has shifted.
15  Using Arduino / General Electronics / Re: Controlling a 5v relay, only getting 2.4v? on: June 28, 2013, 01:03:44 pm
It's such a simple circuit. seems like something must be mis-wired. make sure you don't have the transistor hooked up backwards. In bread boarding, I've done that more than once. check the ohms on your resistor, it's easy to mistake orange for red. Not much else could be wrong.
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