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.
A friend and excellent engineer visited over the weekend and between us we decided to improve the burner a little. The first change we decided to make was to add some insulation. I measured the temperature around the outside of the boiler with a non contact thermometer at approx. 350°F in the area of the firebox. The mounting plate that holds the burner was approaching that temperature as well. The air box was lower but still this is an excessive temperature. The Auger pipe was solid from the hopper to the burner unit and since I have both 4″ pipe and 4″ tube we decided to make a thermal break in the auger feed for additional safety. The 4″ pipe even though it is surrounded by the air box eventually gets warm and since the feed auger has a fair amount of room between the auger and the pipe there is a certain amount of fuel that remains in the pipe and at shut down this can smolder. So to remove this problem and make the unit more safe a redesign was initiated. Adding insulation between the air chamber and the burner with the addition of a thermal break prompted us to take the unit apart, check it over and see how everything was faring as well as make improvements. But of course after the burner and hopper were cut apart and on the bench more improvements were noted. Most of the improvements now fall into minor design for manufacturing type areas, maybe a little less welding and a little more tabbed nut and bolt assembly so minor changes can be made more quickly. Of course being able to pull the auger feed away from the burner assembly without unbolting anything will be a big change and improvement. I am going to make the air box bolt on as well. Should be reassembled for another test on Wednesday.
Of course it wouldn’t be a weekend if we didn’t play with the software. We added a For loop to the thermistor function to improve the accuracy. I added an array to smooth the results using a moving average. But most importantly we found the lingering problem with the LCD characters being garbled. It was a wiring issue. Now fixed it has run 24hours without a problem and I am confident it will stay fixed now. The next step will be to add a capacitor if the problem resumes. I am quite confident it will not be a problem however since it looks more solid even. There is less flickering and more solid character display. So all in all a fun and productive weekend.
Successful overnight run, software required major tweaking but the boiler ran without involvement overnight. I did supervise the process but nothing got hot or got out of the control parameters. My only complaint at this point is chip economy. The setpoint I chose was 160°F which is probably too high for the weather we are having now. The overnight temperature was approx. 32°F and so the circulator just didn’t use that much heat. So I think I will add some software changes to the program. The first to be the addition of a variable called setpoint so I can easily change the set point temperature. Ultimately I need to add a outside temperature thermistor to the internal PC board so the Arduino can determine it’s own set point based on outside temperature. Some other ideas are to relay the draft fan so the flames aren’t quite so robust all the time as well as physically remaking the burner unit to be smaller. All in good time. So far software changes are making a difference so I will try that first.
The flames look consistently great. The burner is working really well. Still having LCD problems and my main goal after getting the unit to run is building a second unit so I can make the unit run the Hot water thermostat as well as try to duplicate the LCD character problems. Of course I could probably call the manufacturer of the LCD to see if they have any technical support. That will be a Monday project.
Above is a picture of the somewhat improved but not final configuration. At least the wires are neat and the smoking problems have been overcome. The new door is pictured, and the burner flame. A photographer I am not.
Success! At least compared to the last burn. Virtually no smoke, although some paint burned off. There is still some lingering smell from duct tape and caulking but overall much better, with no smoke. The burn start/ ash clean out door needs to be rebuilt with hinges, so that is still a problem area, but overall great. The program ran reasonably well, however, I added some hysteresis to the circulator loop to keep the relay chattering to a minimum. At this point I have the oil fired burner locked out, but I think I will reduce the temperature set point of the boiler and it just won’t come on unless needed. There are a list of small items that are required to run a 24 hour test, but I can probably do most of these things tomorrow and be able to be successful with this tomorrow afternoon. One thing that still needs to be done is shop cleanup. But for now, YEAH! Thanks
I changed the configuration of the exhaust fan to pull the intake air from the top of the furnace to the exhaust pipe, which continues down the pipe to help create a vacuum to pull more air from the furnace. I also used hi temp caulking to close up more leaking area making the boiler much tighter. The positive draft, not quite a vacuum and the caulking allowed the furnace to heat to the set point of 160°F and turn on the circulator pump without filling the shop with smoke. The shop did eventually get quite smoky so I shut the boiler down to allow addressing the smoke issue.
The boiler water circulated through the oil fired boiler loop. I turned up the thermostat in the shop to include the shop to be heated and use some of the hot water. The circulator turned on and off several times in response to the returning cooler water, but eventually managed to maintain the water temp for the most part. I probably only ran the boiler for 2 hours total and only 1/2 hour to 45 minutes with the circulator pump on. Great test run though.
The software is still in the prototype stage as well. I wired a potentiometer into an Analog pin of the Arduino to set the on time of the Auger. The dwell time (off time) of the Auger is a fixed 50 seconds. I made the program so that the on time is some percentage of the off time. So the potentiometer can turn the Auger up to a 50 second on time or down to a 1 or 2 second on time. After the first burn it was apparent that changing the parameters on the computer, compiling and uploading was a pain so I wired in a hardware solution. The next iteration of the software needs to have some error checking and data smoothing added into the program to allow the program to make more informed decisions and stop the relay chatter on the circulator pump. So considering I am babysitting today, actually I was told it was parenting, I think I will stick to software upgrades and maybe go to Aubochon’s to see if they have braided fire insulation to seal the burner unit and lighting doors. I think I may order some over center latches for the lighting door to allow easy access but tight sealing and of course more caulking.
The LCD stayed perfect all day yesterday, the other change I made was to put the relays on a separate power supply. I also added back in the clock which does not seem to be a problem to the LCD. The other thing I can productively do today is order another clock and Uno so that I can build another enclosed box to run the thermostat. I miss having the outside temp on my desk and last night since the Arduino was tied up on the boiler I had to be the thermostat for the solar tank. WTF?