13 November 2013
In other news, I built (most of) the hexapod (6-legged) robot mentioned in the last post! It came together surprisingly fast. Which is good, because the Boise Robotics Club meets this weekend and I will actually have something to show them. The firmware is 98% written and the hardware runs!
I found a new program called BlackBoard. It's designed for my circuit board technology of choice, perfboard. (A lot of electronics hobbyists do surface mounted parts these days, but, yuck. Long live through-hole!) It was really nice to spend a few days tweaking my design, moving wires and components around until I was satisfied it wouldn't smoke the first time I plugged it in -- see, it's a lot easier to change things on the screen than with a desoldering tool (which I did end up using a couple times anyway, but not as much as I would have). One super nice feature is hitting a key to show the backside of the board. As you solder something together with perfboard, you place components on the front side and then flip it over to solder on the backside. So being able to see the properly flipped view means you make fewer soldering mistakes as the layout is flipped left-to-right when working on the back.
I still have more debugging to do -- I did my prototype on my breadboard at a nice standard 5 volts, but my battery is 3.4 ~ 4.2 volts so my sensors and things need recalibrated -- I didn't use the commercially packaged sensors the Pololu project lists, I just rolled my own (cheaper and more fun!). Fortunately, in my board design I placed the pins necessary for reprogramming so I don't have to pull the chip to download new firmware -- just plug in a few wires and program the chip while it's still mounted to the robot. Same as the chicken door actually.
And I still need to make legs. Minor detail.
31 October 2013
Here's the bottom of the chicken door board before the tape is applied. The solder-side tracks are wires harvested from Cat5 Ethernet cable.
On another note, I bought a cheap little Lipo charger and a cheap little Lipo cell to make a 6-legged insectiod walking robot similar to this: http://www.pololu.com/docs/0J42/all (be sure to watch the video, it's cute). The Lipo is smaller, lighter, and cheaper than the NiMH pack Pololu used, though slightly more prone to burst into flames so I shall need to add a voltage monitor circuit to ensure I don't over-discharge it.
The charger had the wrong connector, so I desoldered it, and unfortunately, ripped off the positive voltage track in the process. No matter, a bit more Cat5 wire replaced it. Now I have a standard male header I can connect to the battery to charge it.
21 October 2013
Apparently I shorted something that ought not to be shorted and fried my Atmega chip. Since the chip at this stage was solidly soldered to the board, I decided to start over and do it "right".
I now have some 28-pin DIP (no, not a dip as in an idiot, but a DIP as in Dual Inline Pins) sockets and some more Atmega chips on the way. The sockets let me easily replace the chip just by pulling it out, should it get fried again. In the meantime, I'm laying out the board better. This is what I have:
On the left is the dead board after I depopulated it. On the right is the new layout with a new blue clock board. This new board, instead of having soldered wires, has header pins for everything. Also on order are some connectors to er, connect wires to the header pins, and a crimper tool to attach the connectors to wires. The connectors cost 3¢ each, but they make things far neater than the rats nest of 16 or so soldered wires that were coming off the old board in a snarl.
On the new board I'm also leaving 8 digital pins and 1 analog pin available for future expansion (Lemontree wants to add a feeder at some point).
I'm also applying electrical tape to exposed conductors to prevent any more face-palm mistakes.
25 September 2013
Some people like to etch their own printed circuit boards. I've never tried it, but I understand the acid used is nasty stuff. So, I just bought some "perfboard" which is basically a universal circuit board. Connections are made on the bottom side by globs of solder or in the case of my +5VDC rail, a random chunk of wire (a clipped lead from a resistor, I like things that are free). Topside, I made connections with little bits of 24AWG Cat5 wires. (Cat5 is cheap and I had some laying around.)
The project consists of the Atmel Atmega328 AVR microcontroller (the rectangle on the bottom right of the brown board), a ChronoDot real-time clock (blue circle top left), a voltage regulator (green sticky uppy thing top middle), and a twin relay module (off to the right, connected by wires). Not shown are a red and a green LED that I'll aim at the (human) house so we can see if the door is open (red) or closed (green) by looking out the window. Also not shown is the $10 thrift store cordless drill that will actually raise and lower the door by turning a threaded rod like a screw drive garage door opener.
The blue rectangle sitting separately and with the green and white wires coming off it is an Arduino Nano, which is used to download my program from my PC and into the Atmega microcontroller.
The whole thing will be powered by a solar cell (the kind sold to keep your car's battery from going dead) and a little 12V motorcycle battery. To save on battery power, the microcontroller actually spends most of it's time asleep -- only waking once per second to get the date and the time of day from the ChronoDot, calculate the current position of the sun for my latitude and longitude using the TimeLord library, and based on that information activate the relay module to run the motor and raise or lower the door if appropriate. Whew!
The brass brillo pad you see in the pic is something new to me, a waterless soldering iron tip cleaner. It works as well as a wet sponge, and doesn't turn my soldering iron's tip black as much as water does. I also purchased a "sal ammoniac" block to clean built-up black stuff of the iron tip. Makes a lot of smoke and actually works (if the iron is hot enough); these two items should save me some money on buying new iron tips all the time.
10 September 2013
The swamp cooler has one flaw: it's too cold.
If you think that sounds like a glowing endorsement, that's because it is. I've read many opinions on swamp coolers online, and many of them are quite negative. They make your house soggy, some say. It can't compare to the performance of refrigerated central A/C, say others.
Now, I am admittedly biased since I spent many hours and dollars installing mine, so I'm liable to suffer from "sour grapes" syndrome -- I have a lot invested in my swamp cooler, so I would look foolish if it turned out to suck, and I don't want to look foolish. So, I offer the following objective observations:
The performance of a swamp cooler is directly related to outdoor humidity.
The relative humidity in Idaho is typically too high for good swamp cooler performance at night and in the morning. A swamper might only achieve a 5-10° drop in air temperature. But, outside air temperatures -- even in the peak of summer in of July/August -- often fall to 60-65° at night.
The relative humidity in Idaho is typically low enough for an evaporative 20 to 25° air temperature drop the afternoon and evening, when outside temperatures are around 90°.
When outside temperatures rise above 90°, relative humidity drops proportionally and the swamper achieves a 30 to 32° temperature drop.
What does all this mean, qualitatively? When it's cool outside at night, you only need a 10° temperature drop to make the house downright chilly. When it's 90-95° out, you only need a 20-25° degree drop to make the house a lovely 70°. And when it passes 100°, you still get 70° air coming out of the swamper.
In short, it works, and works well.
In fact, on many occasions, it works too well, outputting 65° air and anyone in the family room has to put on a blanket. We could turn the cooler off when this happens, but it's a hassle to go turn the cooler on and off all the time. A thermostat would solve this, but more on that later.
How about humidity?
Well, as I mentioned, Idaho is very dry ("semi-arid", whatever. Locals call it a desert). Many of our family members suffer from dry skin (elbows, knees) so the added humidity is very welcome. Our house has never gotten soggy because we open a few windows halfway, on the far side of the house. Exhaust air is essential for swamp cooler effectiveness! If you keep the windows shut, all you get is wet with no cooling.
Table salt does not clump. Doors do not stick. Furniture does not warp.
Ah, but what about the smell? My answer: what smell?
When our pads were new, they smelled wonderful (I love the smell of aspen). Sadly, this only lasted a month or so. After that, nothing. I have installed a "bleed kit" that constantly removes a trickle of water from the cooler whenever it is running, which brings in fresh water. This means the water is not in the cooler long enough to spawn life forms. Also, each night I run the cooler on "vent only" (the water pump is shut off) which allows the pads to dry. Bacteria and mold have a real hard time growing on dry pads.
But you say, the window thing is an issue: can't leave it running when you're not home (open windows being an invitation to burglars) and it's a pain to keep opening and closing them all the time. Well, this is true.
The solution is up-ducts in the ceiling of each room. These automatically open when you switch the swamp cooler on and exhaust air into the attic (thus cooling the hottest part of the house, killing two cooling birds with one stone). I have some up-ducts, but haven't installed them yet. Maybe next year.
The great thing about up-ducts is you can put a thermostat on your cooler and at that point, it's just like central refrigerated A/C -- set it and forget it, it takes care of itself. I should have that ready to go by next summer too, soon as the up-ducts go in.
At this point, I'm laughing all the way to the bank. At the peak of summer this year, our electric bill was less than $70 (and that includes a lot of irrigation water pumping). Electricity is cheap in Idaho, but from what I understand, most Idahoans pay $100-$150 a month to cool a 1,700sqft house. So the savings are definitely significant.
And while the cooler cost quite a bit more than I expected -- closer to $1,500 -- that's still a fraction of the price of central refrigerated A/C, and I can fix it myself with a screwdriver if it ever breaks. Try asking an A/C tech how much it costs to replace a coil or compressor, and get ready for sticker shock. Even the diagnosis for A/C is typically $100, whereas I can fix pretty much any part on my swamper for less than $100. And I can do it the same day and not wait weeks for the tech to fit me into his schedule.
Swamp coolers are useless in humid environments -- so they are, admittedly, pointless in much of the US. But, in the arid parts of California, east Oregon, east Washington, Utah, Colorado, Nevada, and New Mexico... they rock.
02 September 2013
I'm not smart.
I cut off the lower limbs and tied a couple of ropes to the trunk up as high as I could.
Then I tied the other ends of those ropes to the bumper of my little car. Yay for 1980's bumpers.
Then I cut most of the way, but not quite all of the way, through the trunk just below my ropes. That's probably a good 15 feet off the ground. You don't want to actually cut all the way through, because that trunk could go anywhere and if you're on a ladder, your only escape route is straight down. Your choices then become limited and all of them painful.
27 August 2013
This is just a breadboard prototype. The finished project will be mounted inside the wall in my hallway, with just the display and some buttons visible.
20 May 2013
Today marked the final inspection on the swamp cooler. Since I had to run a short duct from the swamp cooler through the attic to the living room ceiling, I had to pull a "mechanical" permit in my jurisdiction. That's a good thing: improperly sealed ductwork can cost you a lot of money on your heating/cooling bill, so it's nice to have another pair of eyes checking up on your HVAC contractors' (or lazy/cheap homeowners) work ethic. In my case, not only did my cute little baby duct pass, but Lemontree tells me the inspector liked what he saw. Aw, shucks.
Anyway, I learned a couple things. One, ductwork is not a science, it's an art. (And I am not an artist.) Two, mastic will cover many sins.
Mastic is this lovely gluey stuff that's approximately the consistency of sour cream. When dry, it provides an airtight yet flexible rubbery seal, since metal ducts expand and contract with temperature changes. Actually, most of my joints ended up pretty tight so it didn't take much mastic to seal them up. However the final joint just didn't line up quite right... even though I took great pains to use a plumb bob to transfer the roof duct location to the ceiling duct location, I ended up a tiny bit off so the duct is a tiny bit crooked and I ended up with a quarter inch gap on one side of joint. I don't know if 1/4" is a decent tolerance for HVAC pros or if they're all shaking their heads sadly as they read this, but in any case it's not going to leak air any time soon because I put a couple layers of foil tape (NOT duct tape!) on the outside and filled the gap on the inside with about a pint of mastic. Do pros use a spatula to apply mastic? Maybe not, but it sure works great!
Luckily, we had a couple of unseasonably hot days this May so we've already had a chance to actually run the swamp cooler. Our outside thermometer said 96°F, and I'm pleased to report the cooler made Lemontree and the kids cold enough to put on sweatshirts. So, I guess that means it works.
So far it seems ridiculously oversized, though. I got a 5,000CFM cooler with a 1/2 horsepower blower motor for a 1,700 sqft home. The recommendation is to replace all the air in the house every 3 minutes. On low, it moves a good amount of air. On high, it's a freakin' wind tunnel. It's almost like rolling your car's windows down on a highway. So, I fully anticipate running the blower on low 99% of the time. Maybe when it hits 110°F I'll be glad to have a highway speed -- er, I mean a high speed -- available, but for now low is good and costs half the electricity as high... and this thing already uses about 1/3 the electricity of "normal" A/C, so the savings are even more than I expected.
I was right about the noise thing, too. Our neighbor's outside central A/C unit is probably 50 feet away behind a wood fence and I often hear it growling when I'm outside. Our cooler, on the other hand, is almost silent. On low, I can't really hear the blower when I'm outside. The hissing of the water valve letting in a trickle of water is actually the loudest thing, and even that sounds like a whisper at ground level. From the inside of the house, you can definitely hear the hum of the blower motor but it's about the same noise level as a central A/C blower, so it's not objectionable.
In short: I'm happy. :)
02 May 2013
There are two ways to control a swamp cooler; one is line voltage. Line voltage is when you run big full power (120V) wires to a switch on the wall, then run a bunch more big wires to the swamp cooler. That's a lot of expensive wire (copper ain't cheap!) and those switches tend to burn up in a few years when run that way.
I chose the alternate way, which is low voltage. If you have a furnace or central A/C with a thermostat, that's exactly how those are all controlled. Your furnace or A/C has a little transformer in it, that produces a small amount of safe, low (24V) voltage which goes through inexpensive little wires to your thermostat. You'd get a tickle from it, but it shouldn't kill you or start any fires.
Ordinarily, you'd need to purchase a swamp cooler specifically designed for low voltage ($$$), or purchase a $150 conversion kit which is an ugly box mounted to the outside of the cooler. I didn't like those options, so I used something called a RIB from a company called Functional Devices. A RIB is a "Relay In a Box", and a relay lets you use low voltage to control line voltage. Neat, eh? The other nice thing about these RIBs is they're individually replacable, so if one fails I'm just replacing one $20 RIB and not a $150 control board.
So, I tapped into the low voltage source from our gas furnace:
You're not required to do low voltage connections inside a box like you are for line voltage, but I put mine in a box anyway just because I wanted things to be tidy. I'm saving a ton of money by doing this myself vs hiring someone, so a couple more bucks isn't going to break the budget.
The inspector actually didn't like how short I left the above wires, so if you do something like this be sure to leave 6" free length on each conductor. But, the inspector let me slide this time.
Rather than have these RIBs mounted inside the swamp cooler (subject to moisture damage!), I mounted them in the attic on a scrap of 2x6 lumber. Mounting everything to the lumber beforehand let me do most of the work in my cool, clean, well-lit workshop standing comfortably rather than laying facedown in nasty insulation at 100°F:
The blue box off to the right side houses all of the low-voltage connections, so that only line voltage connections exist in the main gray box. (Don't want to mix the two together, for safety reasons.)
The inspector passed my work (and by the way I also got a plumbing permit for the water line and that passed inspection as well) so now I can try to figure out how to install the duct... hopefully before we start getting too many 80°F days!
23 April 2013
15 April 2013
Too busy to update the blog. But, here is a little snapshot of what I've been working on. See, our swamp cooler is mounted between 24" roof rafters, but the 20" duct has to come down through the ceiling, which is constructed of joists 16" on center. 20" duct won't fit in 16" space, basic math theory proved by physics. Solution is to cut a hunk out of the offending joist and reinforce the cut area with "headers". The headers are secured with code-approved steel hangers, and the hangers are secured with code-approved fasteners -- ordinary screws are too weak.
I did everything by the book and to code, though this will not be inspected because no permit was required. When it comes to sawing out part of your house, it ain't the place to skimp. Since we have a low-pitch roof, there is no room to stand or even really sit, so I had to do all this on my belly... rolling around in intimate contact with the insulation. No fun. No fun at all. Spent all Saturday afternoon on it. This swamp cooler had better be worth it!
Now that I have a space for the duct, I'm waiting for an HVAC contractor to supply the duct itself so I can install it. Hurry up and wait...
01 March 2013
The solution? Make a work holding device. This one started out as 1/2" 12L14 (free-machining steel) round stock, about 1" in length. In the back end, a large hole big enough to pass the entire screw (in this case an Allen head, properly called a Socket-Head Cap-Screw, or SHCS) was drilled most -- but not all -- of the way though, to make sort of a cup with the front end still closed.
Then in the front end, I drilled a much smaller hole -- and this is the clever bit -- tapped threads to match the threads of the screw. The length of the front hole is calculated to allow 5 full threads of engagement (4 threads would be sufficient, but I like to over-engineer). This produces a hollow tube. The screw is slipped into the back and threaded in so it sticks out the front, thus:
In essence, I gave my screw a really big head (hey, it happens to all of us now and again). Now I have a nice, big, 1/2" diameter 1" long item I can safely and securely chuck, and then machine whatever I want to on the end of the screw. (In the picture above, the dog point has already been completed.) Luckily, the lathe's normal direction of rotation tends to seat the screw threads more securely into the holder under tool pressure, so things don't go haywire when you start cutting. (Speaking of haywire, my first attempt at this sort of holder ended in an ugly mess because I made it out of aluminum. So, steel is definitely the material of choice for this job.)
When I'm done machining, I just stick the Allen key in the open back end to unscrew my screw from my holder.
In other news, I bought some 1144 steel (A.K.A. "Stressproof"). Not for any particular purpose -- just to have some on hand for as-yet unimagined future projects... and because I wanted to try it. 1144 is about 3 times stronger than mild steel, yet paradoxically, it machines wonderfully. Plus, it's a little cheaper than 12L14, so 1144 is now my second-favorite steel alloy. Still nothing compared to the sheer joy of machining brass, of course, with it's golden fountains of tiny chips; but sadly, brass is over 4x the cost of steel -- making it uneconomical for many applications. :(
09 February 2013
I had actually built a workbench in early January, but the shop was too dark and cold to use it. So, today's little project was leveling the workbench, securing it to the wall (it's a little top-heavy and tippy), and hanging lights.
The bench is made from I think 3 2x4s and 1 sheet of OSB, cut in half and layered 2 deep. It's just temporary, though -- just to get things rolling until I get the nerve up to gut and rennovate the whole shop. The walls of the shop are dirty and full of holes, and because of the holes, we can see there are large sections with no insulation. Also, the old inefficient T12 lights all need to be replaced with modern T8 fixtures, and the existing lights are all in the wrong places anyway (and of course there aren't enough of them).
All this adds up to stripping everything down to the studs, insulating, putting up new walls and ceiling, and running new electric. You'll notice I put electric after walls -- I think I want the electric all surface mount, so it can be extended or reconfigured without tearing into walls.
Until then, I also put up temporary lighting for the temporary workbench. Conveniently, an outlet was right where I needed it to plug the lights into the ceiling. About time something happened in my favor...
08 February 2013
I spent most of January and the beginning of February sick, so progress has been frustratingly slow. The house is livable for now, so I've been trying to get my workshop in some semblance of order. In the beginning of January, I ordered a window-mount heat pump. I'm sure you're all familiar with window mount air conditioners, but here in Idaho, we usually need a lot more heat than cool. A heat pump will cool in the summer, but more importantly, it will heat inexpensively in the winter.
Ordinarily, an electric heater is expensive to run. All electric heaters are nearly 100% efficient, but even though they don't waste power, they sure guzzle a lot of it! A heat pump does run on electricity, but uses about 1/3 the juice as a pure "space heater". So while not as a cheap as natural gas, it's still not too shabby.
Few window A/C units work as a heat pump. Most A/C units with "heat" are merely space heaters. Fine, perhaps, for climates like California, Texas, or Florida where heating is seldom needed, but not so much for Idaho. No, a window A/C with heat pump is pretty rare. In fact, I think Amana is the only company that makes them (and, surprisingly, they're actually still made in the US!).
Now, there are plenty of PTACs (like what you find in many hotel rooms) out there by GE and others that are heat pumps, but they're all 4 feet wide so it's unlikely you'd put one in a window. PTACs are good choices for heating/cooling a shop or garage, but do require a big ol' hole in a wall.
As it happened, my shop came with a hole in the wall above the window -- a small hole though, so rather than reframe, I just got a window unit that fit the existing opening. The good news is, it has plenty of capacity to heat and cool the space, being 11.5k BTU/h. A 19k BTU/h Amana is even available in window-size, but would have been overkill for us -- oversizing a heat pump is almost as bad as under sizing it, as it leads to moisture problems (not good in a machine shop filled with steel that can rust!)
As it happens, my heat pump requires a 240V outlet. No problem, Lemontree and I are already honorary plumbers, so I can be an electrician too, and install one! Actually it's not that simple, I did spend a week or so researching the NEC electrical codes. There are lots of rules to follow, but that's okay as those rules are what keep us from getting electrocuted or having our houses burn down.
After careful study, I applied for a permit, purchased about $40 worth of materials (copper wire ain't cheap!), and pretty much finished in two evenings. I was just about ready to have it inspected, when I got sick again and again. Just as soon as I felt halfway human, I'd get hit with something else. So went about 5 weeks. Finally though, today I passed the inspection and with Lemontree's help, hoisted the heat pump into position. And it even works!
Now that the shop can be a warm and pleasant place to work, hopefully I can get more things done. As long as I don't catch yet another bug...
31 January 2013
First off, it was great to get the chicken coop to a stage of completion that we could put the chickens in there for a whole day with extra food and water so we could visit family for Christmas without having to bother neighbors to care for our hens. We just screwed the egg doors on for the time being and hung the man door. Finishing the coop and building a fence is now going to have to wait for warmer weather AKA ground thaw. We still need to attach the egg doors properly and side and paint the whole thing. We'll need to put up a fence, and I'm considering options to keep the hens from flying over and perhaps keep some predators out. A few days ago, a red tail hawk bumped into the house on it's way down, quail hunting. I'm glad it wasn't a chicken tha got caught!
Corwin has started putting his shop together. He's had to add a new receptical for a heat pump he ordered. I'm sure he will soon have a post about his exciting adventures as they develop.
Inside, we have been working on our "bonus room". We had to tear out part of the subfloor and drywall, as there had been moisture damage. We patched the doggy door hole the previous owners had put in the wall, a doorway that led to the master bedroom, and various other holes in the wall and ceiling, including the hole for the water heater vent that we removed. We tore out wiring as well, deleting two wall switches and a ceiling outlet. After all that, My brother and my dad came over to help me tape and mud the bonus room and the master bedroom for good measure (remember the doorway we walled up?). My brother then textured both rooms for me. I'm so appreciative of his help. He came back three days in a row, using his time off to help me. My dad brought me his paint spraying machine, and after a few hiccups getting it to work right for me (it needed a new filter installed), I primed both rooms, and painted the bonus room a nice pastel yellow. I'm waiting on Corwin to decide on a paint color before painting our room, but he still has workshop on the mind, so I'm waiting (im)patiently. We still need to put in the new subfloor (there was a moisture barrier that protected the bottom layer of floorboards, so we were able to work around it), paint and replace the baseboards, then have new carpet installed.
Nothing comes together as quickly as I imagine, but we are moving along slow and steady. What with keeping up with a household, and flu and cold season taking it's toll, the fact we can get up and get back to work is a great blessing.