Over the summer and fall I have written and tested a number of programs to have the building blocks of a working program. I knew the key this year would be the ability to log data. Of course to log data and have it mean something you have to have good data. So I spent several days working the bugs out of OpenLog, which works but I would not recommend. I also spent some time figuring out a combination of moving averages which resultx in stable data.
Of course the integration process was a train wreck. The arrays used for moving average data smoothing were declared wrong so that bug had to be found and fixed. The Serial LCD needed to be replaced, and my soldering iron wouldn’t work. A few of the functions are timed and there were some issues with those functions. The code for Open Log was not robust enough, once I worked out all those issues, which took most of the weekend, it is finally ready to test.
I had a plow in the shop for repair and soaked up the spilled hydraulic fluid off the floor with some sawdust, actually pellets that got wet. So the hydraulic oil soaked sawdust is in the hopper to be burned. It’s burning now, so tomorrow I should have some excel data which will help me make decisions to improve the software. At this point I am not sure it will be valid however, it is really taking a long time to come up to temperature with the sawdust. Another data point.
It took me longer than I would like, but the hopper/auger assembly is now painted and the electrical box is mounted and the wiring is functional. I have mounted the Arduino and LCD display. That box also contains the board that accommodates the thermistor electronics, which are the sensors that read various temperatures.
The main electrical box is a stainless steel box I picked up used from a scrap yard, putting the frugal in frugaltinker.com. That’s the reason that there are so many holes in the box, however it was such a good deal I thought it was worth it, despite the cosmetics. The cover was just too ugly to leave be, so I attempted to skin the cover with a plate which I plasma cut in “Frugaltinker.com”. This doesn’t show up too well, I probably should paint a background behind it to make it stand out better. Painting a background seems low on the to do list right now, so I think I will skip that task and focus on the burner.
The CNC was invaluable in the production of the electrical mounting plate, mounted inside the electrical box. It was great to not have to drill any holes to mount anything. All the holes were cut with the CNC and fit just fine.
So the final task is complete before the burner is welded up and tested.
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.
The increased air from the second fan did improve the smoke and make the inlet fuel pipe even cooler. It also enabled me to have a viewing port to see if there is flame or if the fuel was adding as expected. But two things happened, the fuel did not flow out of the way so at the bottom of the pipe there was a scree field of pellets which did not move until the previously feed fuel had burned. This situation makes the feeding control very critical. The pace of the feed must be the same as the pace of burning. This alone makes the design unworkable, the process must be more robust than to require advanced combustion calculation, measurement or observation.
The second problem observed was the area of combustion across the pellet field is limited the area of the roughly trapezoidal shape that was formed. This area is significantly smaller than the area of the burner trough. Consequently two things are learned. One the area naturally formed by the falling pellets is insufficient to maintain the water temperature required for my needs, as evidenced by the boilers inability to get past a temperature of approximately 130°F. This alone also requires the redesign since the whole idea is to heat the house. The second conclusion is the area is directly related the heat making capability and thus sizing a burner to a house and feed system is probably quite doable. This seems obvious in statement however, I was thinking that factors such as air volume and burner efficiency would play a larger role. At this point I think I can tailor the BTU’s by burner size and design. I think I will start with the more modest goal of getting the damn thing to work for more than a day.
I’ll admit to being a bit discouraged, however, as January’s calendar said, ” Character consists of what you do on the third and fourth tries”.
To the side see a shot of the burner on the bench in my messy shop. You can see in this shot the approx size of the pellet field that would be burning vs. the potential size of the pellet field if the entire trough was filled.
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.
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.
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.