Tag: power

Power Inverter

I have a terrible habit of thinking of projects that would be neat, starting to work on them, then forgetting about them or otherwise leaving them until some point in the future at which I remember them, and then the cycle repeats.  Well, I’ve been mulling one particular project over in my head for a couple years, and now I’m going to declare my intention to start it and hopefully share it with the world: I am planning to build a power inverter.

Now, the truth is I have started on this project a little bit, mostly by sketches on paper and in LTspice, an excellent,  free (but not open source) circuit simulator.  For those unaware (and who didn’t feel like reading the Wikipedia entry), a power inverter (I’ll probably just refer to it as an ‘inverter’) is a device that converts direct current (DC) to alternating current (AC).  There are a number of applications for this…

  • Running household appliances in your car (shave while you drive!)
  • Backing up servers, medical equipment, or whatever else you want to keep running when the power goes out (UPS)
  • Running normal household appliances on a small renewable energy system
  • Connecting your small renewable energy system to the grid

And so on.  Inverters range from small ones you get at a hardware store, to big ones that can run small villages.  I’m not trying to run a village with this project, nor am I trying to power a significant portion of my apartment.  I would, however, like a small, high-quality inverter, and to really learn how it works.  And, I would like to publish instructions for this online, so that hopefully they will be useful to other people and the design can possibly evolve.

Here are my objectives for this project:

  • Output of 120 VAC, 60 Hz (nominal), 300 watts
  • Input of 12 VDC (nominal)
  • Sine wave output
  • Bidirectional: can also function as a battery charger with a transfer relay, similar to an uninterruptible power supply (UPS)

Now, this isn’t really anything novel.  As I mentioned, there are smaller inverters around, and you might be wondering why this would be worthwhile compared to say buying a small inverter at the hardware store for less than $100.  Well, as I mentioned, I’d like to learn, but that’s not all.  Note the ‘Sine wave output’ requirement.  Most of those cheap inverters won’t have this and will thus produce dirtier power.  Also, I haven’t really found a smaller unit that can act as an inverter/charger, which is something that would come in handy for me – while I do have a largish battery with some solar, it would be nice to be able to charge from the grid with this unit and essentially have a UPS.  Of course, I could get a UPS too, but they’re not really designed for continuous usage, they tend to have dirty outputs, and are designed for charging smaller batteries (usually big enough to allow you to shutdown your equipment, or start up generators or whatever).  Also, for safety reasons, I will NOT being setting this up as a grid tie inverter, meaning it won’t sell power back to the power company.

Now, I would also like to point out that I am not sure how well the design I’m considering will scale.  By this, I mean that were I to build a bigger unit (>1kw), I might approach it differently – this is kind of an experiment.  So, if you’re thinking of building something that you can use to power a chunk of your house when the power’s out in the next hurricane, I’d advise pursuing other options at this point.  (Hey, hopefully this can evolve…)  There are actually several commercial manufacturers that make products (inverter/chargers) that are similar to what I’m building, but work at higher power levels.  I have not used any of those companies’ products, but they do have decent reputations.  Also, if your power doesn’t go out very often, and you just want some quick, cheap backup, a normal gas-powered generator isn’t a bad idea.

I should note that I would not consider this the ideal beginning electronics project; while not impossible it will be somewhat challenging, and will involve high (lethal) voltages.  If you’re unsure of things, feel free to ask here (I’ll try to answer as best I can), and go brush up on power electronics (there are plenty of books on this subject, as well as college classes).  I’ll be saying this again, but whatever you try must be at your own risk.  I’ll try to keep up with this and post more as I go, so stay tuned.  It should be fun.

Lenovo Beep Followup

Well, last post I talked about the power beep on my Lenovo G530 driving me to the point of flashing my BIOS.  Well, I’m proud to say that the BIOS flashing itself went fine.  The downside is, the new BIOS did not stop the beep.  As it turns out this was an upgrade fix for a slightly different model of laptop (the G550, I believe), making this a reading comprehension error on my part.  However, I guess it’s nice having a fresh new BIOS image…

On another note, if you try to do the Windows live cd thing on this machine, I must warn you that it blue-screened for me.  The fix, luckily, was easy – I just had to go into the BIOS and set the hard disk controller to IDE.  Then it went fine.  Also, I used a USB stick to get the BIOS flash exe in the live environment.  However, BartPE leaves USB drivers out, so it won’t pick the drive up if you just plug it in when the computer starts.  A workaround is to leave the USB stick plugged in and then boot up; it should pick it up then.

If/when I figure out how to disable that stupid beep, I’ll post it.  I haven’t had much luck running sudo modprobe -r pcspkr, but I’ll keep trying other things.

Gentoo Not Detecting CD

Alright, so in case I didn’t mention it before, I am running Gentoo again on my desktop.  Things are good, compiling is fun, etc.  However, every once in a while there is a little snag.  Just recently (yes, around 1:30 AM, it’s a night off and I got sidetracked), I had reason to burn a CD (which I don’t do very often).  Well, I stuck the CD in, and Gnome didn’t pick it up.  IE, I installed Brasero to burn it, and it wouldn’t detect the CD in the drive.  That sucks.

As I also run Ubuntu, I’ve gotten used to having things picked up and configured for me, from CD drives and USB hotplugging, to things I never knew existed.  Well, I knew I’d had this CD problem before and had fixed it.  Turns out all I had to do with edit /etc/fstab and comment out a line I had for mounting /dev/cdrom.  (If you run Gentoo, you most likely know what I am referring to here, if not go browse their documentation.)  After that I just took the CD out and a few seconds later put it back in again.  Brasero picked it up and I was off.

In case you’re curious, this CD is a Windows live CD.  Yes, you read that correctly, apparently it can be done.  It’s for my laptop, a Lenovo G530.  I want to update the BIOS, and while I think there are hacks for sticking the BIOS image on a bootable DOS USB drive, I wasn’t entirely confident in that.  (Their site gives you a Windows-only BIOS flashing program.  You can extract the BIOS file itself, though.)  So I looked up how to do the live CD, and set it up in a VM I had on my laptop and transferred it to my desktop, with its faster CD drive.  I used BartPE to do it.

Why would one update the BIOS, you ask?  Well, my laptop, a Lenovo G530 has this nasty habit of beeping whenever I plug the power cord in.  Or take it out.  Or when the battery gets low.  The sound is loud and annoying, and while muting the sound stops it, this a) only works when the system boots up and b) means that if I want to have any sound I have to put up with it.  I usually just mute temporarily, or plug the cord in when it’s off.  But sometimes I’ll be on battery and listening to music through earbuds, when the battery will be nearing the end of its charge and all of a sudden a deafening beep will resonate through my skull.  Well, my laptop runs version 1.08 of the BIOS, while the new version, 1.10 supposedly fixes this.

Also, I removed the the hard drive from my machine first, just so the booted Windows didn’t mess with it.  I also took out the battery, not sure if that makes a difference.  (Someone recommended it when updating BIOS.)  So after this hopefully I won’t have to touch Windows on bare hardware for a while.

Small Scale Solar, and Other News

Well, for those of you in the Rochester area I will be talking a bit about a small solar power system I put together this Saturday at BarCamp.  This is my first time there, and I wanted to do something a little different than the other things that were on the list.  First, though, I have to make up a presentation, which will probably mostly happen tomorrow after my test.

But I have been thinking about it, and so I guess I’ll post a little preview here.  My system is small, utilizing a 10 watt solar panel.  Energy production, obviously, depends on how much the panel is in the sun; since it is not a permanent system, I don’t really have a fixed answer to that other than I’ll take it outside for an hour while we go to play frisbee.  The system is just the panel, a batter, and a charge control.  I use it to run some lights, charge my cell phone and radio, and my laptop.  I guess you could add an inverter too, but I find that most things I want to run I can do directly off of 12 volts (or through a DC-DC boost converter in the case of the laptop, which likes 16 volts to charge the battery.)

This system could be nice to take camping, or to an event of some sort.  While it might not anihiliate your electric bill or make you an ecoviking, it can be useful during power failures and emergencies.  And of course it’s a great learning tool; if nothing else it makes you aware of the fact that electricity has to be produced some how.  (After all, they don’t just pump it out of a hole in the ground, amiright?  At least, never that directly.)  We’re so used to electricity being that cheap stuff that comes out of the wall to power our digital lives, and kill us if we fuck around with it too much.  Well, there is something neat about making your own power.  So come on down to learn more.

Now for some other news.  It is actually starting to warm up a bit here.  The temp has been in the 50s quite a bit, even the 60s sometimes.  That’s a ncie temp, IMHO.  Sun’s out more too.

It was warm in our apartment too.  Warm and steamy, actually.  I went home for Easter, and came back Sunday night to find that the bathtub faucet was leaking, providing a steady stream of hot water for a decent chunk of the weekend.  My roommates had put in a maintenance request, and they finally fixed it on Monday.  It was actually pretty neat, aside from the gigantic waste of water and gas.  Our entire apartment was warm and humid, like a tropical paradise.  The sound of water was also kind of nice, though it was kind of lucky that I couldn’t hear it from my bedroom.

So that’s that.