Home Brew Solar Array
I was getting tired of my solar panel project just resting on the ground in the back yard while I tested everything I wanted to test with it. So, I built this simple rotating solar array. It’s sized to handle 6 240 watt panels, but at the moment, I only have 4 mounted on it. I’ve been sourcing the panels on Craigslist, and buy them when I find someone selling them for around $200. I’ve been pretty lucky in the fact that I’ve found these 4, but it seems like the prices on the panels is dropping by the second. I’m working on a deal right now to get the remaining 2 panels I need for about $150 a piece. Pretty good deal, considering these panels alone have dropped my electric bill by almost $100 a month so far.
Here’s the array in all it’s glory. It’s basically a 10′x10′ frame constructed out of unistrut that is mounted on a 9′ long 2″ schedule 40 cast iron pipe. The pipe sits in a 3′x3′ concrete column buried below grade with rebar tying it into the block and the surrounding earth. I’m fairly certain this thing isn’t going anywhere any time soon. We had some crazy winds this past week, and the whole thing barely even moved when the wind was blowing, which made me feel pretty good about it’s chances of staying upright here in San Diego. The unistrut is attached to the pipe via a simple rotating mount I bought off of eBay, with the mount allowing swivel in both the vertical and horizontal directions. While I would love to build a simple solar tracker and have the whole thing move automatically, I don’t think that I’ll have enough time in the foreseeable future to actually accomplish this. I’ve looked at some commercially available stuff, and the cost is ridiculously prohibitive. I’m using some plug-in grid tie inverters I also purchased off of eBay to tie the panels output into our home electric system. All in all, they’ve been very reliable. the best thing is, when we eventually move out of this house (in a year or so, it’s a rental) I can simply lift the array off of the pole, and take it to wherever we move to. There’s nothing permanent about this system, other than the pole, which I can lop off 3″ below grade, and my landlord will be none the wiser that it was ever there.
We were in a bad spot with our electric use. SDG&E has four tiers of pricing for their residential electric rate. The chart below is a snippet from our bill, showing where we are now.
SDG&E residential rates for February.
As you can see from the chart, we ended up in Tier 3, which wasn’t bad for us. For the last several years, we’ve always been in Tier 4, averaging around 850 kWh per month in consumption. I was able to implement some conservation measures around the house (LED lighting, beating my children to get them to turn lights off, building a lower power home server, and setting the other computers in the house to sleep when not in use) but this still didn’t take us below the Tier 4 threshold, and anything else I did would result in enough pain that I would get some fairly awful feedback from my family. So, the only way to get below Tier 4 was by producing some of our own power. Hence, the solar array. The rates in February were lower than what we typically see here in San Diego, which is odd, as Tier 4 usually whacks us at about $0.33 / kWh. Below is a chart from December of 2011 showing the higher rate :
SDG&E residential rate structure for December 2011.
The eventual goal is to move out of Tier 4 and Tier 3 entirely, and exist in the Tier 1 / 2 realm. This would ensure that we’re paying what I would consider reasonable rates for our electrical consumption. To do that, we need to produce or conserve an extra 100 or so kWh / month, which is definitely reasonable for us. The addition of two more 240 watt solar panels should account for about 40-50 kWh in the worst months, leaving the rest to other conservation measures. Or, we could go on a level pay plan after the Summer months, when we’re producing about twice the kWh/month with the solar that we are now, which would also accomplish the same goal.
Holy hell, it worked.
I’ve been wanting to add some functionality to my whole house power meter. I really wanted to be able to view my data in real time on this blog, and I wanted to be able to store the data in something a little friendlier than a local Excel spreadsheet or .csv file. After doing a little bit of digging around on the internet, and a lot of head scratching and forum perusing, I came up with a pretty simple to implement solution.
The first part of the solution involved getting an Ethernet Shield working on one of my arduinos. I had a Duemilanove laying around that wasn’t doing anything, and two Mega 2560′s that I use for testing and hacking on stuff. The Duemilanove was my preferred choice, as I wouldn’t have to modify it or run any jumpers to get the ethernet shield to work. The problem with the Mega is that SPI is implemented on pins 50-53, and the ethernet shield is expecting it to be on 10-13, so you have to run jumper wires on the Mega from 50-53 to 10-13 on the shield. Not the end of the world, but definitely not convenient. The other problem was that the macetech.com ShiftyVU shield that I was planning on using to drive the ShiftBrites also utilizes pins 9-13 to drive the Shiftbrites via hardware SPI, but I had read that it was possible to use different pins to drive the ShiftBrites via a software SPI. So, I wasn’t too worried about that.
Getting the Ethernet Shield to work was semi-challenging for me. The one thing I’m starting to realize about the arduino is that there’s a good amount of documentation out there, but most of it isn’t particularly thorough, and folks on the forums aren’t really good about posting the solutions they’ve found to issues after they’ve solved them. Most of the threads start out with … “please help me” and end with …”I’ll post the solution tomorrow when I’m back from work” as the last post. It’s frustrating, because you can see that other people have had the same issues you have, but there’s no well documented solution. Oh well. My main issue with the ethernet shield was that I didn’t understand how I was supposed to initiate client connections when I wanted to send data, and that I didn’t have to initiate a server connection every time I wanted to send data either. Once I figured that out, with the help of super-ethernet-sheild-wizard zoomkat (forum post) it was all pretty simple. I included the code I used to get everything working in my post. Read the rest of this entry »
The Arduino / Shiftbrite Power Meter!
I’m amazed almost every day with the new things my kids learn. They’re little sponges that soak up everything around them, and then they puke out what they’ve learned at random times. It can be both endearing, and annoying, depending on what is said, and when. I didn’t fully realize this until the other day when I flicked off the light switch when I left my office, and my son Nate told me that we need to turn lights off to save electricity. He’s three years old, has no clue what electricity is, and yet, here he is telling me that we need to save it. I know he doesn’t fully understand what he’s saying, but I was a little impressed that he was able to link the concept of turning off a light, and the result of turning off that light. I geeked out a little bit and tried to explain to him what electricity was, and why it’s important we don’t use more than we need, but I lost him about two words in to my explanation. I figured the best way to explain to him what turning lights on and off actually does wasn’t to tell him about it, but rather show him something that would react to the lights going on and off. Hence, the ShiftBrite Power Meter was born.
I’ve used other whole house power meters in the past, and while they’ve suited my needs fairly well, they didn’t work well in translating the data into something my family could understand. My wife just doesn’t care about the difference between 1 kW and 2 kW on the display meter – to her, it’s just a meaningless number. My kids, well, they’re still learning how to count, so it’s doubly meaningless to them. The other problem with those meters is that they were a pain to maintain, with the wireless flavors constantly running out of batteries, or the wireless receiver losing connection. The less expensive ones didn’t log the data, and the more expensive ones that did log the data typically used GooglePowerMeter to store and display the data, and that service recently shut down. So these were the major obstacles I needed to tackle with my own power meter. I needed a visual display of our current power consumption that my family would understand, and I also needed a way to store the data delivered from the power meter and convert it into something useful for me. Read the rest of this entry »
The Pumpkin Project – 2011
Don’t have a bunch of time to write anything up on this one, and there’s folks that want to see the video. So, here it is.
In a nutshell : we set up some LEDs in some pumpkins and wrote a little code to make them respond to music. Fun stuff. More on the details later when I get a few minutes to write.
New Z-Table for the Laser
While I was in Chicago this past week, I received the new Z-Table that I ordered from En-Gravs Laser and couldn’t wait to get it installed. I was using some perforated metal sheet as the top of my Z-table, and the relatively large amount of surface area was causing a decent amount of reflection on a lot of the material I was cutting. The new grid has almost no top surface area, making it a much more suitable surface for the Z-table. Also, it’s MUCH flatter than the metal sheet I was using, which is making my cuts much more consistent.
The other advantage of the new grid style table is that it’s easily removable. It came with some wooden brackets with some alignment tabs on them that I bolted into the Z-table extrusions using some 20mm hex head screws that I countersunk into the wood brackets. The table slides on or off the wooden brackets and doesn’t require anything to secure it to the table, which is very, very convenient. I can remove the table easily, and then slide in the rotational engraving adapter I also received in the mail last week right in. No tools are necessary to make the switch. Pretty cool stuff.
I’ve made a couple of cuts on the new table, and it seems to be working great. The smoke from cutting gets pulled right out the exhaust, and there’s very little reflection on the underside of my parts. The white-ish powdercoating is getting stained, but I don’t think that’s a big deal at all. Aesthetically it’s not very pleasing, but functionally it makes no difference.
The new Z-table with the first thing I cut on it. A small letter-cube.
A close-up of the countersunk bolt and the alignment tabs.
Laser Improvements
I had a little free time last weekend, and I made some improvements to the laser. I had received revision 2 of the laser interface board that includes the Pololu stepper drivers for all three axis integrated onto the board, making it much cleaner to wire up than using separate stepper drivers. Switching over from using a separate break-out board / driver set up to the integrated board is fairly straight forward. Most of the original connections from version 1 of the board can be used, but a couple of things have changed. The most noticeable one is the addition of a RJ45 plug interface for the connection from the laser power supply to the board. I’m not sure that there’s an advantage to this, other than the fact that most network cables that you can purchase utilize a shielded cable, which could help cut down on some of the interference between the high voltage laser power supply and the electronics. The other change worth mentioning is the addition of the ability to switch between controlling the laser power via the front panel pot or a PWM signal from an external controller, such as the RetinaEngrave or the DSP. This is definitely an improvement over the verion 1 board, and is controlled via the addition of a toggle switch on the front interface panel. Installing the version 2 board necessitated a change to my front panel layout, and so I figured now was as good a time as ever to go ahead and cut a new interface panel that incorporated the new switch. The pot voltage is displayed on the upper left, the pot is the far left knob, the laser fire button is next to the pot, and the new switch is just to the right of the voltage display. I am going to go ahead and raster in labels when I receive my DSP here in a few days. I’ll end up filling the label lettering in with some sort of white paint.
The new front interface panel
Fire in the Hole!!!!!!!!!!!!!
So after about a month of tinkering and assembling, the laser finally came together. Thanks to the wonderful plans over at Buildlog.net there was very little in the way of frustration during the entire project. The assembly is very straightforward, and if you actually read most of the forum and support threads before and during the process you’ll most likely not have any issues. The one portion I spent the most time on was the final laser alignment – but most of the frustration came down to the fact that I had a different type of mirror mount than most people, and I had it set up in a manner where it would most likely never align properly. That’s all taken care of now, and all the mirrors are aligned, and the whole thing is just pretty damn awesome.
The business end of the laser, along with the first mirror and the Z-axis stepper are all shown.
The gantry - with the air assist and cable carrier.
Yearnin’ for Burnin’.
Opulence. I has it. This has to be one of the best lines ever used in a commercial. Ever.
It can also describe what my wife thinks about my hobbies. She has used a plethora of words to describe them, but the one that always is included is “expensive.” While she always looks for the practical in things, I look for the awesome. And unfortunately, being awesome usually costs a lot of money. Well, it used to, at least.
So a few years ago I was in the throes of one of my amazing business ventures that ultimately petered out and died. I’m not going to detail it here, as they have all petered out and died so far, so by leaving it vague you can use your imagination and take your pick of which one it was. One of the things I needed to do for this was cut some thin insulating material and a bunch of gaskets. Back in my Navy days, we did this all by hand. If you needed a gasket made, you whipped out a sheet of neoprene, chalked it up or traced your part out on it, and went nuts with a razor blade. I was originally prepared to do this for the pieces I needed, but the thought of making hundreds of pieces like this made me want to vomit. I talked to a few people I knew about this, and one of them suggested that I have them laser cut. I had never heard of a laser cutter, but go figure, I had another friend that had access to one, and was totally cool with letting me use it. He said he’d even help me set it up and cut the stuff that I needed. Pretty amazing. Long story short, a few beers and a few hours later, I had the hundreds of pieces I needed, all perfectly cut on this laser cutter. The precision was amazing. And here I was thinking that the only thing that lasers were useful for was attaching them to sharks heads and letting them cut up the local super hero. Go figure.
If you’re reading this and you know me, I know what you’re thinking right now. You know what I was thinking right then. I HAD TO HAVE ONE OF THESE THINGS. It was just too amazing. Well, looking into it I found that the average cost of one of the basic lasers capable of doing what I needed it to do was somewhere between 20-40k. Yeah, not happening. I’ve done some pretty crazy scheming before, but there was no way I was ever going to put that one past the wife. Not if I wanted to retain all my limbs, or more importantly, my favorite appendage. So I filed it away in the Cool Stuff I’ll Never Have category and moved on. I eventually purchased a mill, which can do several of the things a laser can do, but about 100 times slower and not nearly as well. Read the rest of this entry »