Category Archives: Nerd

Building a DIY Off-Grid Solar Bank on my Roof

I’ve been fascinated with solar energy ever since I was a kid and my brother had a toy with a motor attached to a mini solar panel that you could run under a strong light. In recent years, solar panels have come down in price and now seemed like a good a time as any for me to experiment with it a bit. I took a week long staycation from work a few weeks ago, and in preparation, I did a bunch of research and bought a ton of components to set up an off grid solar thing.

I chose to go off-grid because I didn’t want to deal with actually putting the power back into the grid and all the bureaucracy involved (I’m not sure if my power company even buys power back), and the scale I’m working at is super small anyway. Here are the components I used, and why I decided to go with them. They might not be the best choice, because I have no idea what I’m doing, but even so, I learned a lot in the process.

The Battery

As I was building an off-grid solar charging system,  I needed something to store the energy gathered by the panel. My initial goal with the project was to charge the battery on my electric bike. The bike is something like 12Ah at 48v, so overall the capacity is about 580 watt hours. I only let the bike battery drain to about 80% at most, so I wanted to charge about 100 watt hours at a time.

The type of battery I got was a lead acid sealed AGM battery, which is apparently pretty safe and commonly used in this sort of application. After doing some research about these batteries, it sounds like they also last longer if you only let them discharge to about 60-80% of their capacity, so I got a battery that holds 660 watt hours (12v * 55 Ah). I could probably have gone with a bigger battery but this one only cost about $100.

I had no idea what sort of connector this battery used when I bought it, but it turns out that it’s a pretty common connector that uses a bolt. The inverter I ended up buying worked out of the box with it and I ended up buying a box of additional eyelet adaptors to make my own wires.

The Solar Panel

I wanted a panel that would be able to charge up my battery to a decent level each day. I ended up getting probably more capacity than needed, but I can always expand my project later. I bought a 100W polycrystalline (because it was cheaper than mono) panel by Renology because it had good ratings and a good price to watt ratio. The connectors on the panel are MC4 so I ended up buying some additional cable so I could connect the panel to a charge controller.

The Charge Controller

I ended up getting a cheap charge controller that came at a discount in exchange for me writing a review. I was going to buy one that looked similar anyway, though I’m not sure if it’s the same manufacturer or just a knock off of the one I was going to buy. Either way it is the perfect size for my project at 10A and shows info like the current voltage level of the battery and the amperage going into the battery as well as the load coming out of the usb ports and the load out connectors.

I assumed you were supposed to connect the load out directly to an inverter but I read a few posts about how that would be a bad idea. I’m guessing too much load would fry your charge controller.

The Inverter


I was looking for a pure sine wave inverter, which is supposed to be more efficient and nice to your electronic devices, but I couldn’t find one under $100 so I ended up getting an 800W inverter that seemed pretty solid. As I mentioned earlier, the connectors just worked for the battery, which was nice. I only use one outlet at a time, so I haven’t tested if this thing can actually throw out 800W, but it’s probably a good rule of thumb to get an inverter with more capacity than you’ll need on average anyway. My bike battery charger uses about 140W and a Macbook charger will use 80W. I’m not sure how many watts that is after efficiency lost with the inverter but it’s probably not too terrible.

Putting it all together

After getting all of the parts I realized that I was missing the connection from the charge controller to the battery. I ended up buying some ringlet adapters that would fit the battery and cut off part of the long wire I bought to make a new wire. This worked better than I thought it would. After that, I was able to connect the panel and battery to the charge controller. I was able to read that the panel was giving something like 3 amps to the battery, which was amazing to me at the time.

I also connected the inverter to the battery and was able to run my bike charger. I attached my Smart Things outlet in between the outlet and the charger so I could monitor how much voltage the battery used. It’s interesting because once the battery reaches a certain charge, the charger tapers down its power usage slowly. Finally, I placed the panel on the roof, which was kind of difficult considering how tall the roof is and how short my ladder apparently is, plus how heavy the panel was and how much I’m able to lift above my head while also balancing on top of a ladder…

Here’s some photos of the system running just inside the door to the roof. I’ll probably set up a plank or something to drill the charge controller and inverter onto, since right now it’s a little janky.

This is the charge controller, battery and inverter charging my bike battery and an iPhone.
This is the charge controller, battery and inverter charging my bike battery and an iPhone.
The highest amperage I've seen is about 6, where I suppose the most the panel can give is 8.3 if it was on the surface of the sun.
The highest amperage I’ve seen is about 6, where I suppose the most the panel can give is 8.3 if it was on the surface of the sun.
Solar Panel
This is the solar panel before I got it on top of the roof

Hopefully you found this interesting and are already planning an off grid solar system of your own. I’m happy to say that my ebike is now powered 100% by my project, as well as a bunch of electronics in my house. Also, my house has become a lot more valuable in the case of a zombie apocalypse.

Strange Copy Pasta in Developer Resumes

A sample of some UIViews
A sample of some UIViews that are basic “functionalities” in a “Multi-view Application”

So for the past few weeks we’ve been trying to hire for a contractor position to work on our iOS app. Along with the rest of the team, I’ve been reviewing resumes on a really corporate looking website that have been submitted by recruiters on behalf of candidates. It’s an interesting exercise because the resumes are almost all in the same exact format and after a while, they really start to look the same. In some cases, this is because a candidate has been rejected and resubmitted accidentally.

While scanning through a bunch of resumes, my coworker Will noticed a bullet point that actually appeared in more than one person’s resume:

Experienced in creating and custom UIViews, Table Views, Tab Bars and Navigation Bar, which are some basic functionalities in a Multi-view Application.

There are a few things that stand out about this. The sentence itself runs on and on, and the grammar used is pretty dubious. Also, the inclusion of this into an iOS developer’s resume tells you nothing because every iOS developer should have experience with these elementary UI elements, and the sentence even sort of explains that at the end. The fact that it appears in more than one resume is surprising, since it’s such a stupid thing to include in your resume to begin with.

I was curious about this bullet point, so I suggested that Will paste the phrase into Google. Here’s an interesting slice of the results:

While there’s not a direct match, there are links to resumes which have slightly altered versions of the same phrase. The part that is mostly shared is the “…which are some basic functionality in a Multi view Application.” If you google for that, you will find pages and pages of resumes with a bullet point similar to the original. Will even started a tally of “mutations” of the phrase with added embellishments at the end, or with slightly better grammar.

I was curious which other phrases in these resumes were common, so I tried googling some of them. Some that I found that had become memes were:

  • Strong Knowledge of Software Development Life Cycle (SDLC) with strategically designing and implementing the software, debugging, fixing and maintaining the software.
  • Developed apps using various iOS design patterns (MVC, Delegation, Target-action and Slide-out Navigation).
  • Proficient in Memory Management: Automatic Reference Counting (ARC) and Manual Reference Counting (MRC).
  • Mobile Application Development (iPhone/iPad) using objective-C, UIKit, Core Location, MapKit, Cocoa Touch and Cocoa Service Frameworks.

I have a few guesses as to why these are in so many resumes verbatim. It could be that the candidate simply copied and pasted the bullet points from a friend’s resume and hopefully actually has those skills. Another could be that the recruiting firm offered to touch up their resume for them and did so lazily. While it’s easy to attribute this to malice, it’s probably just good old fashioned laziness. After all, if it works for so many developers, it should work for you! Either way it looks terrible for the candidate and it’s frustrating for people doing the hiring to see such a lack of originality. I already have to go through more than 30 resumes; I don’t want to think I’m going crazy with all the feelings of Deja Vu.

My recommendation to developers would be to write, in your own words, what you’ve actually accomplished. Resume writing is annoying, and no one likes doing it, but the downside to plagiarism is that I toss your resume out and assume you’re a terrible person. Also, I’m secretly hoping that this blog post becomes the top Google result for all of these copied bullet points so any curious resume-reviewers realize they’re not going insane. Also, feel free to nitpick my own outdated resume which you can find here on my (way outdated) portfolio site.

I haven’t gone in depth at all to discover more of these copied phrases, but I’m willing to bet that a big percentage of bullet points in resumes are simply ripped off from other resumes.

List of Possible Apple Watch “Gates”

Everyone I know loves a good Apple product-based trivial controversy. There was Antenna-gate, and Bend-gate which happened just last year. Back when the first iPhone came out, Apple dropped the price a few months after release and early adopters were pissed. No one can say if there will be a real issue with the watch, butI figure it would be fun to make a list of potential ones.

  • Battery-gate (the battery doesn’t last long enough! I can’t wear it to bed!)
  • Bend-gate 2 (the wristband bends too much! It doesn’t bend enough!)
  • Snap-gate (the wristband cracks and snaps! WTF is fluoroelastomer anyway?)
  • Crown-gate (the digital crown breaks off! It spins too fast!)
  • Siri-gate (random people shouting “Hey Siri!” can control my watch!)
  • Shave-gate (The Milanese Loop is shaving my wrist hair off!)

Edit: Thought of a couple more this morning:

  • Left-handed-gate (can’t wear watch on right hand, digital crown doesn’t spin right!)
  • Sunglass-gate (can’t see the screen while wearing polarized sunglasses at a certain angle!)
  • White-band-gate (white sport band gets dirty too easily!)

I doubt any of these will happen, though Battery-gate seems most likely. Maybe something completely trivial and impossible to predict will ruin the watch launch. What sort of non-issue do you think will fill up the news cycles?

Google Play Vs. iTunes Match

I signed up for the Google Music beta a while ago and promptly forgot about it. I was either too busy to check it out or unimpressed with the feature set. I recently took another look at it after it was renamed to “Google Play.” It’s suddenly making a bit more sense now that I’m trying it out again.

Google Play (I’m really just talking about the music part) lets you upload all of your music to Google’s servers. This step seems kind of dumb but I guess for legal reasons they can’t just recognize your music and use their own copies of songs. I’m sure they’ve got the technology to do it. Anyway, once your music is uploaded you can play it from “the cloud.” While this seems like something so simple that Dropbox could do it, it’s the details that matter. In this case, Google offers a pretty neat interface to listen to your music (and buy more, if desired).

I haven’t used iTunes Match personally, but from what I’ve read, it seems to do something similar. iTunes Match will scan your music library and “match” them up with songs in their database. If a song isn’t on your iPhone but is in your library, you can download and listen to it from your device. So far, it doesn’t seem like there’s a desktop component of iTunes Match besides iTunes (meaning you can’t listen from a website). Also, iTunes Match costs money.

What I like about Google Play is that there is a web interface, so I can listen to all of my music at work without having to download iTunes. I complained earlier on Twitter about how there isn’t a native app for iOS that lets you listen to your Google Play stuff, but there does happen to be a web based player that seems okay. iTunes integrates more easily with your library (no need to actually upload stuff) but seems more rigid about re-downloading music.

Overall, it seems like Google Play is the better service. If it had a native app for iOS it would be the clear winner. Eventually I would like to lower the amount of space on my phone that I’m using for music, which would allow me to have more apps, photos and videos. Hopefully the two services continue to develop and compete with each other to the point where they’re both improving.

Thoughts on Textbooks on iBooks

I was thinking about the latest news from Apple, that they were partnering with textbook publishers to bring cheaper textbooks directly to the iPad while at the same time releasing an application for anyone to publish iBooks for the Apple Bookstore.

Perhaps I am being cynical, but it’s always appeared to me that the main business model of a textbook publisher is to slightly tweak versions of a textbook, altering page numbers and quiz questions in order to force students to buy newer editions instead of used ones. Perhaps the industry is thinking that iBooks will eliminate the used book market, and they’re probably right. But this could also have some negative (for publishers) side effects as well.

Apple is lowering the distribution costs of textbooks dramatically. Assuming that schools actually pay for a set of iPads for each student, it becomes trivially easy (with the iBook publishing software) to create free textbooks for schools. Who would want to give textbooks away for free? Teachers. There are cases of teachers self-publishing for their own schools, but for this idea to really work, I think teachers would need to collaboratively create a textbook that meets either regional or national standards and release it for free on iBooks. If you don’t believe this will happen, take a look at Khan Academy.

Previous attempts to create free textbooks have been hit or miss. I am not quite sure how popular Wikibooks are in the classroom. The problem is probably that of traction and scale. Previously, no one has created a standard for e-textbook distribution. Apple is doing that with iBooks. The beautiful part is that they’re bootstrapping it with traditional publishers who are probably digging their own grave.

Of course, this could play out in a number of ways. Maybe iBooks will prove to be too costly for most public schools to adopt (I’m guessing this is very likely). If only private schools or schools with a lot of funding can support them, it may not become worthwhile to create free textbooks for all.

What I’d hope to see is a slow adoption of iPads in the classroom using iBooks as textbooks. Once a critical mass of schools is using iBooks, free textbooks will be developed and adopted by certain school districts and spread to others.

I’m glad to see that Apple is trying to “disrupt” (I lose some points here by using a word I hate) the textbook industry, and it’s awesome that they’re partnering with that industry to do it. I’m really looking forward to seeing how this plays out, hopefully for the benefit of our education system.