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Tuesday, July 3, 2018

Time-lapse of nesting robins being fed by their mother

A robin decided to nest under the solar collectors on the south side of my workshop this year.  The nest is about 5ft off the ground and I have been watching since the first little blue egg was laid several weeks ago.

They all hatched a week or so ago.

It is now July 3, and they are coming along nicely.  I can watch the mother robin flying in and feeding them from the window in my utility room.  What surprised me is the long gaps as she foraged for food.  Up to 20 minutes could go by as they waited patiently with beaks open.  The video was shot at 1 frame per second (about 30X real time), it is edited down so it is not too boring.


Sunday, April 8, 2018

Metal detecting - my new hobby

Last year I binge-watched the British TV series "Detectorists" (available on Netflix and Amazon) which is a comedy/drama about 2 quirky English mates who share a passion for metal detecting.  Don't call them "detectors" - that is the machine, as you quickly learn!  I highly recommend watching the show and I was captivated by the idea of digging up history, relics, coins and just about anything including "can slaw".  (Can slaw is detectorist slang for a soda can that has been chewed up by a lawn mower.  These and pull tabs are the bane of our existence because a detector sees aluminum as precious metal and pull tabs could be a ring).  


Detector, tools, pinpointer and finds from December 2017
So last fall I bought a metal detector, pinpointer and the related equipment that includes digging tools, too belt and cleaning brushes etc.  I started by practicing on my rural property and quickly found some coins and assorted bits of metal, I was hooked!  Unfortunately the ground froze a few days later and snow covered the ground for most of the winter.  So I was stuck watching other detectorists on YouTube and learning skills from them.  I also joined several Facebook detecting groups.  Basically I was going to Detectorist University all winter!

Now it is April and the ground has thawed I'm starting to explore the historic sites around my small Maine town.  My first day was uneventful but enjoyable, all I found was a few rotted modern coins - known as "clad" to detectorists because they are all plated and not solid silver like the old quarters used to be.  Contemporary pennies are copper plated zinc and don't hold up well under ground, but old silver coins tend to come right out of the ground all shiny.  Oooh!

Then on my second day, the second hole I dug turned up an amazing find.  It is a silver flashed brass medallion honoring 300 year of ship building in the nearby town of Bath and dated 1907.  Wow!  I immediately offered it to the local Historical Museum and they were grateful to accept it.


So by now you may be wondering what does all this have to do with living sustainably?  Well it's not all treasure.  There is a code of ethics for metal detectorists that, among other things, requires that you remove everything you dig.  This makes it easier for the next person that might detect in the same area.  On almost every dig you tend to find a variety of trash that includes, nails, rusting steel parts from old farm equipment and fixtures, old beer and soda cans and pull tabs.  Also lead bullets dating back to muskets and lead flashing from roofs.  Much of this can be recycled!  So I plan to store this "scrap" until enough accumulates to take it to a recycling center.

Another basic ethic of the hobby is to leave the land the way you found it.  So all holes on public and private property are filled back in.  And we are assiduous about getting permission to dig on private land.   Beaches are different, and most public beaches allow metal detecting and filling holes is not that big a deal, but we do haul out all the trash - and the occasional gold ring or silver coin!

I have started a new blog called: "Guy Digs It Up" so you can follow my adventures there.

Wednesday, March 7, 2018

How I design an electronic product

I thought I would share the process I go through to design an electronic product.  I have been doing this type of work since the mid 1980s and while the tools and parts have changed, the process has remained much the same.  As an example I will show how I designed my own product which is a Differential Temperature Controller designed for solar heating systems.  


This device controls fluid circulation pumps that move heat from solar collectors to storage tanks.  I sell these products from my ART TEC Solar web site.

I begin by designing the schematic in CAD (Computer Aided Design).  This is the hard part that requires a lot of research to find the right components and then figure out how they interconnect.  In most products these days there is a microcontroller chip that is programmed to perform all the functions.  More on that later.  Selecting the right microcontroller begins by deciding how many things it needs to connect to or control.  These include buttons, LED indicators, LCD (Liquid Crystal) text display, and connections to external parts like pumps, sensors and power source.  The schematic drawing defines how all these parts connect to each other.
Next I design the circuit board (PCB) in CAD.  The layout software imports the signal connections from the schematic making it easier to ensure all the right connections are made.  This PCB is the physical embodiment of the schematic and involves carefully placing the parts such that the interconnections are optimized.  Key parts like the controls and screw terminals need to be placed for ergonomics and easy access.  For me, this is the fun part because it is a lot like creating an artwork and I enjoy making an aesthetically pleasing layout.
The location of every part has to adhere to electrical AND functional rules and the size of the circuit traces has to be scaled to the amount of power it has to carry.  Circuits that carry more current are wider like the green ones along the bottom in the design above. The green represents the conductive traces on the bottom side of the board, and the red are those on the top of the circuit board.  A great deal of thought goes into every minute detail to optimize size and cost.
The parts need to line up to make assembly by robot or hand easier.

Once the design is complete the file is sent to a fabricator that makes the bare circuit board.  This is a fiberglass board with plated copper traces connecting the holes where the components get inserted.  For volume production, they are tiled up into groups to facilitate machine assembly.  

Once an assembly machine has been programmed to insert all the parts, it can just copy the sequence to the rest of the boards on the panel.  For hand assembly, boards are separated and parts are inserted by hand and then hand soldered on the back.  In my design, parts are installed on both sides.



Once a prototype is assembled and tested, the next step is to write computer code for the microcontoller chip.
I write in BASIC language and have been coding in some form of that language for over 40 years.  The code defines the functions of how the device responds to inputs like buttons and sensors.  The heart of the code defines the functions of what the device does.  In this case how it responds to sensor readings and when it decides to activate a pump.  It also displays real-time temperatures on the LCD and all the interactive menu features.  The code is them compiled into machine code and downloaded into the flash memory in the chip in much the same way you save a file to a thumb drive.

Finally, I design the front panel and case.  Often for my clients projects, I work with a product designer who does 3D CAD design.  In this case, I used an off-the-shelf basic box and set up tooling to make cutouts using the woodworking equipment in my workshop.  It would have been prohibitively expensive for me to design a custom enclosure and have molds made for injection molding a low volume product like mine. 

The front panel of this product is a membrane that I designed and had fabricated.  It is flexible so that a light touch can move the membrane enough to actuate the switches behind.  It has clear windows for the LCD screen and a green LED indicator.

The final step is to assemble the whole product.  All the parts get screwed or glued together and the membrane is adhered on to the front.  Here is one that I use in the solar heating system for my workshop.

The process of developing this product took dozens of hours over several weeks.  Finally I have a product that has done relatively well in the niche market of the DIY solar heating world.  I set everything up to be scalable from making them by hand to volume contract assembly.  In boom years I contracted an assembly company to make batches of 100 pieces.  Otherwise I just build them by hand myself and it takes me about 30 minutes to assemble.  I call this my "get rich slow scheme" as orders come in almost every week. Over the years I have sold over 200 of this particular model and have two other models that have sold over 1000 pieces total. 

Many of my clients start out by ordering 1000 products for test marketing, then scale up once they have created a demand.  Most volume manufacturing is done off-shore, but for under 1000 pieces there are companies in the US that can be competitive.

If you have a great idea for an electronic product, visit my Product Design page and contact me.

Wednesday, February 28, 2018

Replacing the battery in my Kindle Fire HDX 8.9"

I have had my Kindle Fire HDX for over 4 years now and I like it a lot.  It is my go-to device for social media, email and web browsing while at home.  Recently the battery has been lasting only a few hours - previously it would last over a week of normal usage.  So I decided to replace it.  I found a deal on ebay for about $25.00 which is a LOT cheaper than replacing or upgrading to a new tablet!  I found a instructions on ifixit that shows how to open up the Kindle and replace the battery and it did seem a bit daunting, but I'm an engineer dammit!  It turned out to be quite challenging, but I got it done without ruining the tablet.  At one point I did puncture the batteries (there are 2) and smelled a strong solvent odor, but nothing exploded or got hot so I proceeded.  Those batteries are glued in there quite firmly, and it took about 15 minutes to pry them free.  Replacing them and re-assembling the case was relatively easy.

From a sustainability standpoint I'm pleased with the outcome.  I can responsibly recycle the old batteries at Lowe's.  Also I'm not contributing the the consumer culture that drives people to upgrade their devices every year or so.  Plus I have delayed the day that I will have to recycle this great tablet, and I saved a bunch of money.  I do wonder how these things are taken apart and recycled given how much trouble I had.

Here's a brief photo summary of what I did:
 Here is the replacement battery and the relatively useless tools that came with it.
 
The blue spudgers broke and I ended up using a flat blade screw driver and my trusty Swiss Army knife to pry the case open.  There was a tiny specialty screw driver tool that was needed to remove 4 small internal screws, but it was for a smaller screw.  I was able to grind down the tip to make it fit.

Here's the case opened up and the display disconnected and off to the left.

  
You can see that I had to do horrible things to remove the batteries!

 
Here's the back of the device after I got them out. 

I don't recommend this for the faint of heart or those not "tool enabled".



Thursday, February 8, 2018

Solar and snow

The first morning after a snow storm is often sunny.  This morning (Feb. 8, 2018) was a good example and I got up early so I can clear all the snow off my solar panels and collectors.  Yesterday's total was about 8" capped with a layer of ice.  I have a snow rake that can reach up about 25 feet with multiple extensions.  Each different type of snow requires a different strategy.  Sometimes I can just whack the panels and it all breaks loose in big chunks.  Other times I have to chip away at it.  Today I worked my way up from the bottom.  Some big areas broke loose and came down hitting me in the legs which is why I wear waterproof slickers.  That stuff is heavy!

Here's a time-lapse of the process:

Obviously the sooner I get everything cleared, the more free electricity and heat I get.  Maine is at the 43rd parallel and we get a lot less sun in the winter so I want to optimize every Watt.  My electric bill is at the minimum connection fee for most of the spring/summer, but jumps up quite a bit in the winter due to my increased use of electricity for heating and the reduced solar.




Sunday, January 7, 2018

Repairing the tankless propane boiler for my solar augmented heating system

4 solar collectors shown at right
When I moved to Maine in 2001 I converted the open barn on my property to a well insulated workshop.  I also designed and built a heating system that uses solar and propane to heat the radiant concrete slab on the ground floor and baseboard radiators on the 2nd floor office/lab spaces.

The system relies heavily on the Bosch Aquastar BS124 tankless propane boiler that has performed flawlessly since it was installed with only token maintenance.  (You can see a system diagram and live performance charts on my web site.)  Unfortunately it recently failed dramatically due to a prolonged period of extreme cold. 

In the images above you can see the storage tank that accumulates solar heated water during the sunny hours of the day.  Above left is the boiler that automatically brings the water temperature up to 140F when it is lower than that.  In the dead of winter I am lucky to get 140F in the tank so the propane boiler runs a lot.  To reduce the propane consumption, I use my wood stove.  The drawback to the wood stove is that when lit it pulls air into the building and that comes through the powered exhaust vent above the boiler.  Originally, the boiler vent had a flapper valve on the outside to prevent a back draft, but I had foolishly removed it.  So what happened this winter is we got a prolonged period of very low temperatures with night time temps dropping below zero a lot (see the red line below).
(lost data on Dec 28 for some reason)
So on December 30th when the wood stove was running and the heater was off - the cold back draft got down to -15F and eventually a pipe burst in the top of the heat exchanger:
Heater running AFTER repair - arrow shows location of the burst pipe
The arrow points to the section of pipe that blew open.  I immediately researched replacement parts and found a source for a complete replacement copper heat exchanger and in a panic - ordered one online for $350.  But then after calming down, I realized that the damage really wasn't that bad, and that I probably had the plumbing skills to repair it since I had plumbed the whole system myself!
Here is what the burst pipe looked like when I looked closely at it.  It was fairly simple for me to gently hammer the lips of the burst out section back together after draining the system down below the leak.  Then I carefully sanded the whole area around the cut to expose clean copper.  I wiped on a lot of paste flux and warmed it all up with a blow torch.  By gently applying solder, I was able to fill the crack and build a layer of solder over the whole area.  Problem solved and I canceled my order for a new heat exchanger!
There is no running water in the building so in order to re-fill and pressurise the system I had to drag a garden hose across the yard from the house.  This was challenging with 8" of snow on the ground and day time temperature peaking at 10F!  I had to pre-warm the 2 - 50ft lengths of hose in front of the wood stove to loosen them up first!  But it all worked out and it has been holding 50psi pressure for over a week now.  And of-course I made a new back draft flapper for the vent to prevent frigid air from being drawn in again.

Problem solved!  And I saved $350 in replacement parts!  Incidentally the whole building only uses about $200 gallons of propane a year at a cost of about $400 in a good year.  This is very inexpensive and due to the great insulation, interior storm windows and about 1 cord of firewood that I cut for free on my property.