Auger Feed Rebuilding, Step one a DIY Record

After last winter’s experience,  I  decided to start from scratch on the auger/hopper assembly.  I varied the height several times through different burner designs.  Now it looks  like it was modified once too many times.  The other main reason to rebuild the hopper assembly is the difficulty removing the burner from the boiler because it must stay balanced.  I don’t remember exactly my thoughts at that point, I probably just had two wheels around the shop and was in a hurry.

2011 Hopper and Auger Assembly

2011 Hopper and Auger Assembly

So this fall I am rebuilding the hopper with a different auger drive system, and additional wheels and supports to make it much more robust and simple.  The foundation of  improvement in the new assembly  is the ability to draw the parts in SketchUp as well as cut the parts with the CNC. Here’s a view of the cut out parts.

The parts laid out I call the saddle, angle iron, and side alignment plate.

The parts below are the angle iron plate with the side alignment plate. The angle iron plate is tabbed to fit into the slots of the side alignment plate, this way the parts are self aligning and jigging. Adding strength and ease of assembly. This makes the welding so much easier.

Finally here is the assembly on the welding table ready to weld, note the threaded rod, which also aids in the rigidity and ease of adjustment to make sure all the pieces are square and parallel prior to welding.

Unwelded auger drive weldment ready to be welded

And finally the partially finished welded assembly, this assembly will be the foundation to cantilever the auger in the feed pipe as well as support the auger drive motor and gears.

End view of the welded assembly

The CAD designed parts combined with the CNC, combined with self jigging design for success make a nice finished assembly with light material for cost savings combined with good strength.


Feed improvments fix the LCD garbling!

The sprockets have been replaced and improved with key ways cut into the jack shaft and auger.  This allows positive feeding without slippage.  The jack shaft placement was constrained so adjustment of the chains is limited to what linkages can be removed or replaced with half links and adding a slack tension device on the slack side of the roller chain.  With this complete the LCD problems appear to be fixed.  Without proper tension the chain did not ride on the sprockets smoothly and the tension could take up suddenly adding a jerk to the system.  Without this mechanical jerk in the system the motor can work more smoothly allowing the LCD to not get the power fluctuations that garble the display.  The feed problems appear to be fixed but in the last test the unit ran for four days without fail and at this point although there is a marked improvement that time has not been surpassed.  Next on the list is the hopper extension to allow feeding of two bags of pellets.  This will allow 16 hours of run time without any software improvements.

Top view of roller chain drive of auger feed


Good test for the boiler with -5°F overnight temperature

I restarted the boiler with a friend on Friday afternoon on the 13th of January.  At present it is Sunday morning at 6:45.  Thirty nine hours since starting, in that time the temperature has dropped to a low of -5°F which is the current temperature and the fuel usage has been a total of 5 bags.  The house is still comfortable and has not shown any dip or problems in maintaining temperature.  The only noticeable differences are two things.  The lack of the oil fired boiler running which I can hear upstairs and always makes me a little twitchy.  The second difference is the temperature of my office.   My office is off the utility room which holds the furnace and so is normally quite warm after a cold night.  Today it is the temperature the thermostat is set to maintain.

A few numbers, I paid $215/ton for the pellets, so the cost per 40 lb bag is $4.30.  The hours per bag is approx. 7.8.  This will need a  longer time average to confirm but is probably a reasonably good number so in rough terms this is 3 bags per day for a cost of $12.90/day.  I looked back to see if I had a furnace run time data which I did have a limited amount.  On October 17, 2007 the furnace ran a total of 4.1 hours on a day that had a high of 51 and a low of 33 for a total Heating Degree Day of 22.7.  (Heating Degree Days are calculated as (in °F) 65-(day’s max temp-day’s min temp)/2 or to restate 65-average temp) .  Taking the furnace run time as 4.1 hours x nozzle rate of 1 gal per hour this translates to 4.1 gals usage for a total cost at $3.85 per gallon of $15.78 for one day relatively mild day.  Yesterday’s HDD calculation using a high of 29 and a low of 11 yeilds and average of 20.  So 65-20=41.  Using a simple ratio of HDD/Furnace Run time would calculate to a furnace run time of 7.4 hours per day for a cost of $28.50 per day.  Contrasting this with the pellet costs yields a savings of $15.60 for that one day.

So is that accurate?  That was a lot of math using some not very exact calculations.  The math was done correctly but Heating Degree Day calculations are notoriously rough.  Many oil companies have moved onto more sophisticated methods and of course this is just a snap shot of one day.  But as an reality check  at this point I am confident 5 tons of pellets would easily get this building through the winter for a total cost of $1075.   If I used 800 gals of oil throughout the heating season this would cost me $3080 at a cost of $3.85 per gallon.  So yeah I think the numbers are reasonably accurate if not conservative.  Wait until I try chips at a cost of $40/ton……too fun.


Changed feed sprocket

The New Year practically demands resolutions and change for the better.  So with that constant improvement theme in mind I am publicly stating my goal to lose 15#’s and so  I am starting from  195.7.  My second resolution is the constant improvement of the boiler.  So here we go……

Auger feeding failure  due to the motor stalling demanded the  sprocket change  on the auger motor feed assembly.   The sprocket I chose  doubles the torque available for feeding pellets.  Since the shaded pole motor is constant speed the program had to change to double the auger run time.  So taking the data I had gathered I changed the program in two ways.

New sprocket added

I changed the times to accommodate the speed change  demanded by the sprocket change and I changed the paradigm to have constant run time and vary  the dwell or off time.  The increased torque is a vast improvement and since the change it has had no problem feeding even  adding an entire bag of pellets at one time.

A second advantage of the change is the improvement of the LCD display.  I think that this problem is now fixed since the LCD has been running without garbling the characters for several hours, long past the time when the LCD would normally have failed.  By increasing the torque the auger feed motor is running at less amp draw and so it feeds back less to the relays.  I also grounded the relay in a more positive way.

LCD display


Real world vs. Bench Top

I’m a big proponent of having some skin in the game.  If you don’t you are fooling yourself.  I learned that in the financial markets.  If you can trade on paper you have a better chance of succeeding in the real world trading but when you have real money involved sometimes you can’t make the decisions needed.

That seems to be the case with the LCD display.  After having worked out some basic electrical issues the display worked fine for 3-4 days with the relays tripping but no motors hooked up.  Now that the motors are hooked up again it seems to be garbling the LCD.  So, the only assumption I can make is there is some kind of electro-magnetic field  or a bad ground that is interfering with the LCD.    The motor is a shaded pole motor which has a large electromagnetic core which no doubt radiates interference for the controller.  Below is a picture of a similar motor.As a fix I think I will twist the LCD wires so they are less of an antenna and see if using some tin foil to shield inside the project box as well as above the feed motor and see if I can improve the ground.


Added hopper and auger feed motor, LCD problems still

Yesterday I added a hopper to the auger feed and mounted the auger motor.  By depending on my memory I found that I did not have any of  the #35 chain I thought I had and so I had to order some from McMaster-Carr.  Their website is the best I have found and their service is great, so I should have the chain on Tuesday or Wednesday and a test burn is planned for then.  I need to finish up a few minor issues on the boiler, and then it is time for a water test for leaks on the KBS coatings job.    The LCD is now working better I no longer have the garbled characters, however I am finding that the thermister readings go to zero on the display, but again not in the Arduino loop.

At this point I need to finish the boiler ash clean out door, weld up a hole where the tank strap wore through the tank when it was mounted on the truck, line the inside with fire brick, and hook up a removable chimney flange, make the sensor wells and hook up the plumbing, sounds like a lot, but in reality is probably only two days work.  The weather looks mild for this next week but it is really time to finish up and make the boiler work.  I have one other major project in the shop which I need to finish but when that’s complete the decks should be cleared for design of experiments on this boiler, starting work on the next iteration and PLOWING!

If anyone understands the issues with the LCD better than me, please let me know, since it is frustrating to experiment until it works instead of understanding the issue thoroughly.  Here’s the code.

/*
Circulator pump controller

This code turns a circulator pump on by closing a relay, simulating a thermostat.
A thermistor in the solar storage tank measures the temperature and if it is below a certain value
then the relay closes, the temperature of the tank is displayed to a LCD as well as the outside temperature
on the third line of the display the state of the circulator pump is listed. The program smooths the data from the
solar tank to avoid relay chatter, and include a RTC to decide what time of day the heat should be on for the hot
water heating. The time that is given to the RTC comes from the computer so as soon as possible after compiling upload
to the Arduino to make the time as accurate as possible.  The time should be within a minute which seems close enough for
my purposes.

The two thermistors are attached to analog pins 0 and 1, the relay pin is digital pin 8 and the LCD pins are listed below
The Real time clock SDA pin is attached to analog 4, the RTC SCL pin is attached to analog pin 5

The circuit:
Inputs
* Thermister Solar Store, Analog in 0
* Thermister Outside Temp, Analog in 1
* RTC SDA, Analog pin 4
* RTC SCL, Analog pin 5
Outputs
* Relay, Digital pin 8
* LCD Pins Date 2,3,4,5
* LCD Pins RW/E Pins 11,12

Created 11/14/11
Michael Clark

http://www.frugaltinker.wordpress.com

*/
#include <math.h> // include the library code for thermsiter functions
#include <Wire.h>
#include <LiquidCrystal.h>  // include the library code for LCD:
#include “RTClib.h”

//define function to calculate the temperature in fahrenheit for Analog pin 0
double ThermisterTank(int RawADC) {//beginning of function
double Temp;
Temp = log(((10240000/RawADC) – 10000));
Temp = 1 / (0.001129148 + (0.000234125 * Temp) + (0.0000000876741 * Temp * Temp * Temp));
Temp = Temp – 273.15;            // Convert Kelvin to Celcius
Temp = (Temp * 9.0)/ 5.0 + 32.0; // Convert Celcius to Fahrenheit
return Temp;
}//end of function
//define function to calculate the temp in fahrenheit for analog pin 1
double ThermisterOut(int RawADC1) {//beginning of function
double Temp;
Temp = log(((10240000/RawADC1) – 10000));
Temp = 1 / (0.001129148 + (0.000234125 * Temp) + (0.0000000876741 * Temp * Temp * Temp));
Temp = Temp – 273.15;            // Convert Kelvin to Celcius
Temp = (Temp * 9.0)/ 5.0 + 32.0; // Convert Celcius to Fahrenheit
return Temp;
}//end of function

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);  // initialize the lcd with the numbers of the interface pins
//char buffer[5];//gobetwino example

//int count;   // declaring an integer for count
int Solar_Relay = 1;     // init relay toggle to off.
#define Solar_Relay  8   // Arduino Digital I/O pin number 8
// Define the number of samples to keep track of.  The higher the number,
// the more the readings will be smoothed, but the slower the output will
// respond to the input.  Using a constant rather than a normal variable lets
// use this value to determine the size of the readings array.

//smoothing variables for Thermal storage
const int TSTnum=10; //Thermal Storage readings array
int TSTtemptotal=0; // Thermal Storage tank temperature
int TSTtempaverage=0;// Thermal Storage tank average
int TSTarray[TSTnum]; //Thermal Storage reading array
int index=0;  //index for Thermal storage array
int count=0; //initial count for average
//smoothing variables for Outside temp
const int Outnum=10; //Outside temperature reading array
int OutTotal=0; //declare variable and set to 0 for outside temp total
int OutAverage=0; //declare integer variable and set to 0
int Outarray[Outnum]; //decleare array for outside temps
int index1=0; //index for outside temp array
int count1=0; //initial count for average
//section for time keeping
int hour;
int minute;
int pmhour;
int lcdcount =0;

int Outsidetemp;
int test;

RTC_DS1307 RTC;

void setup()
{//Begin Setup section
Serial.begin(9600); // initiate serial communication
lcd.begin(20, 4);// set up the LCD’s number of rows and columns:
lcd.clear();
delay(75);
lcd.setCursor(0, 0);// set the cursor to column 0, line 0
delay(75);
lcd.print(“Solar   Outside”);// Print a message to the LCD.
delay(75);
digitalWrite(Solar_Relay,1); //turn circulator pin off
pinMode(Solar_Relay, OUTPUT); //Arduino digital pin 8 output
Wire.begin();
RTC.begin();
RTC.adjust(DateTime(__DATE__, __TIME__));
// initialize all the readings to 0:
for (int thisReading = 0; thisReading < TSTnum; thisReading++)
TSTarray[thisReading] = 0;
for (int thisReading = 0; thisReading < Outnum; thisReading++)
Outarray[thisReading] = 0;
} //End setup section

void loop()
{//Begin Loop section
//Thermal storage tank temperature smoothing section
TSTtemptotal=TSTtemptotal-TSTarray[index];  // remove reading from array
TSTarray[index]=int(ThermisterTank(analogRead(0)));
TSTtemptotal=TSTtemptotal+TSTarray[index];
index=index+1;
count=count+1;
if (index>=TSTnum)
{//start if section
index=0;
}//end if section
if (count<=TSTnum)
{//start if section
TSTtempaverage=TSTtemptotal/count;
} //end if section
else
{//start else section
TSTtempaverage=TSTtemptotal/TSTnum;
}//end else section
//end Thermal storage tank smoothing section
//outside temperature smoothing section
OutTotal=OutTotal-Outarray[index1]; //remove reading from array
Outarray[index1]=int(ThermisterOut(analogRead(1)));  //get the Outside temperature reading
OutTotal=OutTotal+Outarray[index1];
index1=index1+1;
count1=count1+1;
if (index1>=Outnum)
{//start if section
index1=0;
} //end if section

if (count1<=Outnum)
{//start if section
OutAverage=OutTotal/count1;
}//end if section
else
{//start else section
OutAverage=OutTotal/Outnum;
}//end else section
//end outside temp smoothing section

/*
Start relay on/off section, want circulator pump to turn on if the following conditions are true, tank temperature is
below 120°F and the time is between 4pm and 9pm.  All other times the tank temperature can float.  Note: Three conditions can happen here
1) not in the time frame, circulator off, this is the else section to the initial time check 2) you are within the time constraints and are below
or above the setpoints, turn circulator on, and 3) you are within the time settings and in between the temp settings, leave circulator off.
*/
if ((hour>=16) and (hour<21)) //condition 1
{//start if section
//this section turns on the relay to control the thermostat wire to run the circulator pump to heat water
//if the temperature of the thermal storage tank is below 100°F
if (TSTtempaverage < 120) //change this temp if you want to change the lower limit
{   //code within brackets applies if above condition is true
digitalWrite(Solar_Relay, 0);    // turns Relay On
} //end of the if true section
if (TSTtempaverage >125) // change this temp if you want to change the upper limit
{  //code within brackets applies if above conditions are true
digitalWrite(Solar_Relay, 1); //Turns relay off
} //end of the if true section
}//end if section
else //not between the hours above
{//begin else section
digitalWrite(Solar_Relay, 1); //Turns relay off
}//end else section

if (lcdcount>=10)
{// start if section

//This section prints the thermistor readings to the LCD
lcdcount=0;
//Serial.print(lcdcount);
lcd.clear();
delay(75);
lcd.noAutoscroll();
delay(75);
lcd.setCursor(0, 0);// set the cursor to column 0, line 0
delay(75);
lcd.print(”                    “); //clear line
delay(75);
lcd.setCursor(0,0); //reset cursor
delay(75);
lcd.print(”                    “);
delay(75);
lcd.setCursor(0,0);
delay(75);
lcd.print(“Solar   Outside”);// Print a message to the LCD.
//Serial.print (TSTtempaverage);
//Serial.print (OutAverage);
lcd.setCursor(0,1);
delay(75);
lcd.print(”                    “);
delay(75);
lcd.setCursor(0, 1);// set the cursor to column 1, line 1, line 1 is the 2nd row
delay(75);
lcd.print(TSTtempaverage); //print to the lcd should be the Solar Store temp if thermistor is hooked up properly
delay(75);
lcd.setCursor(8, 1);// set the cursor to column 1, line 1, line 1 is the 2nd row
delay(75);
lcd.print(OutAverage); //print to the lcd should be the Solar Store temp if thermistor is hooked up properly
delay(75);
//end lcd printing section
//Time section, gets and displays the time
DateTime now = RTC.now();
hour=now.hour(),DEC;     //get the hour from the RTC chip
Serial.println(hour);
minute=now.minute(),DEC; //get the minute from the RTC chip
Serial.println(minute);
//changes from 24 hour time to AM, PM
lcd.setCursor(0,2);
delay(75);
lcd.print(”                    “);
delay(75);
if (hour>=13) //PM Section
{//start if section
pmhour=hour-12;
lcd.setCursor(0,2);      //set cursor to the 1st column, 4th row where the time will be displayed
delay(75);
lcd.print (pmhour);
delay(75);
lcd.print(‘:’); // print :
delay(75);
if (minute<10)//adds a “0” if the time is single digit
{//start if section
lcd.print(“0″);
delay(75);
}//end if section
lcd.print(minute);
delay(75);
lcd.print(” PM”);
delay(75);
}//end if section
if (hour<13) //AM Section
{//start if section
lcd.setCursor(0,2);      //set cursor to the 1st column, 4th row where the time will be displayed
delay(75);
lcd.print (hour);
delay(75);
lcd.print (“:”);
delay(75);
if (minute<10)//adds a “0” if the time is single digit
{//start if section
lcd.print(“0″);
delay(75);
}//end if section
lcd.print(minute);
delay(75);
if (hour>=12)
{ //start if section
lcd.print (” PM”);
delay(75);
}// end if section
if (hour<12)
{// start if section
lcd.print(” AM”);
delay(75);
} //end if section
}//end if section
//End time section

//checks condition and writes accordingly
lcd.setCursor(0,3);
delay(75);
lcd.print(”                    “);
delay(75);
test=digitalRead(Solar_Relay);// prints the state of the circulator if in the middle ground of temp
if (test==1)
{// start if section
lcd.setCursor(0,3);              //sets cursor to column 1, line 3
delay(75);
lcd.print(“Circulator Off”); //prints “Circulator Off to lcd line 3
delay(75);
}//end if section
if (test==0)
{//start if section
lcd.setCursor(0,3);              //sets cursor to column 1, line 3
delay(75);
lcd.print(“Circulator On “);      //prints circulator on to lcd line 3
}// end if section
//End Relay on/off section
}//end if section
lcdcount=lcdcount+1;
delay(1500);
//Start Gobetweeno Data collection section
// lcd.setCursor(6, 3);// set the cursor to column 8, line 4, line 3 is the 4th row
// lcd.print(millis()/10000);// print the number of seconds since reset:
// if (count == 30)
//{  //does everything within the brackets section if the statement is true goes on otherwise
//  Serial.print(“#S|LOGTEST|[“);//if gobetwino is running this will log the data
//Serial.print(itoa((int(ThermisterTank(analogRead(0)))),buffer, 10));//sends data to file for inside temp
// Serial.print(“,”);// comma to delimit the data between inside and outside temps
// Serial.print(itoa((int(ThermisterOut(analogRead(1)))),buffer, 10));//collects outside temp in file
// Serial.println(“]#”);//gobetino command ending
//   count = 0;
//} //end of the if true section
//   count = (count + 1);
// Serial.println (count); //display count on the com monitor window

//End Gobetweeno data collection section

}//End loop section