I know it’s early on the calendar but my focus is starting to shift back to my heating hobby. After two years of experimenting I have a proven performer with both the mechanical unit and the software I used last winter. I could change nothing and go through the winter fairly smoothly but there is always room for more improvement. So this is my plan: 1) Build a new unit very similar to the proven unit I have been using but with greater feed range capability to allow the unit to feed wood chips as well as pellets. By building a complete new unit I can always roll up the proven unit after the experiment is over and the data collected and resume heating without a hiccup. 2) Make slight modifications to the boiler to allow a larger interface plate between the feed unit and the boiler. This will allow a greater range of experimentation with burner designs. 3) Continue making small experimental changes to the working pellet unit such as a vibrator for ash removal, different burner designs, different draft designs. 4) Continue to make changes and improvements to the software. To start I would like three modes of operation. Continuous, run for some amount of time, and run until a set time. I changed the software to run to a set time by calendar date last spring but it was built into the software by date not menu or button choice. I would like to have the option of running for a few hours for both experimentation and also to occasionally heat hot water and be able to choose these options by menu. This fall I am sure I would like the unit to be able to take the chill off and then shut down. 5) Build a chip dryer. This is going to get to be a priority , I know the days are getting a little shorter and it is amazing how much less solar there is in the fall. Time to giddy up on that one.
I know I have to prioritize the work, and work as time and cash flow allows. But I think the first step will be to make a new interface plate and boiler opening. This will allow standardization for the next design and this work can be done while there is no particular need for heat. I went dumpster diving the other day and got a great new electrical box, so I guess I can get going on the that part of the new burner feed. I like free stuff. I may hit that dumpster again soon.
In the mean time it is still summer and there is still sailing weather.
It may not be cabin fever, more just a general malaise. That midwinter everything is working and I don’t want to take it apart feeling. But I have several projects half done at this point. I am waiting for headers to install the Ethernet card so the Ethernet update project is on hold. The CNC plasma cutter is apart awaiting a new lead screw for the y-axis. This is to remove the vibration issues I have been experiencing. I am changing from a single start to a five start lead screw. I will lose one fifth of the resolution I have presently but that will still be plenty of resolution for this application. But the big news is I am finally going to move on building a new firebox. It’s time to retire the over the road fuel tank turned boiler. Well maybe not retire, just move onto a new home. Anyone want to buy this working boiler? I would consider selling the auger and burner feed as well as a combination. The unit is located in Newport, NH if you would like to see it working. It won’t be available until it’s replacement is built. It is after all heating the house, shop and hot water. But I am hoping to have the replacement built before the end of the heating season for some testing. If you are interested drop me an email at: firstname.lastname@example.org
A quick reminder of what the combination looks like, this has successfully burned pellets, chips and to a limited degree sawdust. Ideally you would be a person who can tinker as this is a prototype unit.
The software, Arduino and LCD display all very solid and work very well.
I added gasket rope which I bought at a local hardware store, which is made to replace the gasket material which comes in a wood stove door between the burn plate and the boiler. This gasket changed the Magnehelic vacuum reading from .1″H2O to .4″H2O. That I thought would make the flame a bit more vigorous. I also made the holes in the bottom of the burner larger to allow the ash to fall through. Lastly I made minor changes by tacking some material across some holes and making more air holes in the ramp plate which the pellets fall down.
The main differences in this graph and the previous day’s graphs are at approximately minute 273 pellets were added and the sawdust which had been running finally ran out. As you can see it had enough energy density to overcome the demands of the circulator circuit. The biggest problem after that came at about 341 when the program allowed the temperature to go past the set point of 140°F The only explanation I could come up with is the division by different types of declared variables was not allowed and yielded a result of zero. I was dividing an unsigned long which is an integer by .8 to increase the Auger Off time by 20%. Since you will not get an integer when you do this the program may not have liked this result. The Arduino language is a slight variant of C++ . I have since made all the variables doubles we’ll see if that works. Today’s burn will be a better test of the burner floors ability to let ash fall through. Sawdust is very difficult to burn. It’s also difficult to get the ash to fall through the burner floor. I think this is because the air cannot get around the sawdust sufficiently to burn it completely and hence it smolders in clumps instead of falling through the grate. The burner when I pulled it out to inspect it was definitely not clean of ash but did appear better than yesterday.
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.
I often have to cut multiple parts, so when I do, I take the opportunity to experiment a bit. In this series of cuts I changed the amperage of the Plasma cutter, a Hypertherm 45. Hypertherm plasma cutters are American made, designed and built, only about a 45 minute drive away from me. I still haven’t gotten my free T shirt for buying and registering the machine but I guess that’s another story… anyway, amazingly enough there really is not a lot of difference in the dross or slag between the three different amp settings I tried. I’ll keep experimenting to try to optimize the cut quality and speed of the CNC machine, plasma cutter combination.
The auger pipe connects the burn plate which attaches to the boiler and forms the interface between the auger feed and the boiler/burner units. I took a piece of 6″ pipe and welded it to the boiler plate and this attaches the plate to the auger feed via screws that tighten. With this assembly I can detach the auger and hopper and test a different burner simply by loosening 6 screws. Modular design for ease of design changes and maintenance.
I attached the hopper plate first because this determines the wheel height required. I slotted the holes in the saddle plates so that there is about 3/8″, or about a centimeter of adjustment up or down adjustment. Then after careful alignment I assembled the entire assembly with clamps and threaded rods. I did cut and weld in some cross pieces with gussets
This will make maintenance of the boiler, ash removal, scraping of the burner holes, boiler tube cleaning very easy by simply rolling the auger/hopper assembly out of the way.
In this step I mount the auger drive motor, it has a built in right angle drive and speed reducer which adds torque. The motor comes complete ready for wiring and mounting using four screws. Again I drew up the parts in SketchUp and then cut them out on the CNC plasma cutter, it was almost too easy. The further I get down this path the more I take advantage of the CNC’s capabilities. Note the rounded corners, I also added an extra hole on top of the motor mount plate to make adding a wire routing clip easier in the future. I remade the worm drive plate to improve some of the adjustment capabilities and added at the same time some decoration, rounded corners and used less material.
I used a Lovejoy type shaft connector to connect the motor to the worm shaft with a Buna-N spider in between to minimize any vibration or backlash to the motor, although with the worm and worm gear combination there should be none.
Notice the title didn’t say completely finished since the last few steps are to improve the acme screw feed as well as add a water table, ventilation system and wire up a better connector for the torch control. But the paint looks great and the electrical components in a box is great. The part you see cut is intended to be the plate that is the interface between the boiler and the burner. I call it the burn plate. It will go into the opening in the boiler, the holes in the very bottom will allow a resistance heater to light the biomass either pellets or chips, the holes above are for draft. The large hole in the top center is for the auger feed and the remaining holes are on the left, a fire detector sensor and a hole to be tapped for attaching the sensor. The two holes in the upper right are intended to be the swivel point and observation port to observe the flame. I drew the part that you see pictured up in Google Sketch Up. What really impressed me about Sheetcam is that the piece to swing and hide the flame in the observation port was made at the same time from the scrap that was cut out of the auger hole. Sheetcam automatically figured out the hole in this swinging part should be cut as a hole with the offset of the kerf to be on the inside of the hole, then cut the remaining profile as a outside kerf, then cut the auger hole as an inside hole. This was all done in the correct order automatically. Cool! Sheetcam is a great program.
I finished the assembly of the two carriages on the x axes of the CNC machine. The y axis is mounted and this next week the goal is to assemble the carriage to Acme nut connections and build the linear carriage for the y axis. So if all goes as planned next weekend or sooner could be the first prototype test of the machine, the z axis will not be workable but I am sure I can find a way to attach a pencil the axis to see movement. That is a great goal for the week.
My SparkFun package of an FTDI Adapter board and and second board will allow me to reload the firmware on the OpenLog board I ordered in January. I am dreading this a bit, electronics and computer area things are my weakness so I am a bit nervous but will tackle this job and test in a example sketch this week. I’ll bet that will take any free time I may have up but will get me that much closer to my goals.
Earlier I finished the piping for the the two additional zones. A quick recap, one zone will allow a boiler to heat the tank that is normally heated by solar. The second zone is really not a zone but the piping and circulator pump that will add heated water from the chip boiler.
The solar water tank, or solar thermal store has two coils in it, the first coil is heated by the solar loop on the roof. This coil is physically lower in the tank so that the heated water will rise and the sensor controlling this coil is lower as well. This allows the maximum storage from the tank from solar at all times. The second coil and sensor that is intended to be heated from the boiler is mounted higher. The water at the top is hottest and therefore the least amount of energy will be needed and the maximum amount of free energy is used first. Of course solar is not free, it still requires a circulator pump but I assume it to be negligible and therefore in this context free.
Knowing this and assuming that I am going to use an Arduino microcomputer in the process anyway, I am intending to implement the solution in two steps. The first step to wire and shrink wrap a thermistor and run the thermistor back to a breadboard, and display the temperature on an LCD. If the temperature is below a certain value, digital write to a relay to turn on the circulator pump. If the temperature is good, do nothing.
In the second iteration of the solution my plan is to add a time chip to the system and make the process more efficient. The logic is this:
8am, no real need for hot water, and there is a good chance the solar will heat the water.
4pm, heat water and maintain until 8pm if needed.
8pm-8am maintain a minimum, lukewarm temp. We’re not a shower in the morning family. Of course on the weekend the program will have to be different.
To implement this 2nd iteration a real time chip will be required. I have found a few, one at sparkfun.com
and a second one at
I am inclined to the second link, the board is cheaper with a built in battery holder and battery shipped with the product for $14.99
And the yourduino option for $9.00