Ones and Zeros

I’ve finished the installation of my solar power system in the popup camper. I think of it as a pilot to a possible house solar system that’s rather more-expensive.

I talked about this a little before, but in short we have a 30 Watt panel feeding a 65 AH battery with a charge controller. This is a larger battery that I think I need, but was a standard size that I could buy. Having more reserve won’t hurt. When I tested it, I propped up the panel as below. (Yes, it still generates power in the shade, but less.)

The battery, in turn feeds several 12 Volt DC uses: LED lighting strips and four 120mm computer fans for ventilation. These are almost silent (I bought them specially for that). Then there’s the 120VAC inverter for AC power. That makes a sound with its vent fans so we’ll only use it when we need AC. That’s for charging a computer, etc.

The first steps to doing a solar installation are to figure out the electrical load you want to supply, and thus the amount of power you’ll need. My load is 200 Watts/day. Pretty minimal. Your house uses much more than that. Read your power meter for your house’s load. Or, for a smaller system like mine, calculate your load. There are online tools for this at places like the www.altestore.com which also has many helpful articles too.

Once you have an idea of the load, then figure the power you’ll get from the panels. Mine is for use in the longer sunny days of summer, so I figured 5-6 hours of sun per day. For a house, you’d need a year-long average of hours of sun/day, and adjust that for shade from nearby trees, hills, etc. The amount of power helps determine the size and number of the panel.

You also will need to know how many days reserve power you’ll need. If you’re an off-grid system, this is more critical since you can’t pull power from the mains. If you’re connected to the grid, you actually don’t need much (or perhaps any) batteries. Your reserve requirements determine the size of your batteries.

Then, you need a charge controller. Overcharging or overusing your batteries can shorten their life drastically. Since they’re expensive, it makes sense to spend a little money on a device that controls that charge level. It has to be sized for the amperage and current your panels provide. Wire this together with wiring for the amperage you’ll be passing through the wires. Put some fuses in place (I have one leading to the battery, and one from the battery.)

Then, you need an inverter, this converts the DC power to 120VAC power. Some systems use 12 VDC like mine, but larger systems will use batteries in series at higher voltages.

My inverter is the small blue device here. This is my battery, the small gray thing is my charge controller. The large black cable and the device it attaches to is a parallel system for plugging the camper into campground-provided AC power that we’re not using. Since I took this photo, I’ve added the outputs from the battery in terminal strips that the LED lights, fans, and USB power converter’s plugged into.

Most of the work was in the wiring and in figuring out the connections. In any real project the minutia of fitting the parts into what’s already there is a big part of things. Most of the connections are soldered, a few are crimped as I trust crimping less.

A less minimal system would have amperage meters to show the charging current and load current.  Some more expensive controllers have a monitor to show power stored, etc.  But this is a vacation-purposed system though, if the power dies it isn’t a big deal.

More planning on my part would have simplified the installation as I would have just ordered all the parts and wiring I needed from DigiKey, Jameco, or Mouser Electronics. But I tried to buy local from Radio Shack. Radio Shack is no longer a parts store and hasn’t been for years; I hereby give up on them. Since I like to see the parts and handle them when planning I really miss a local parts store. If I still lived in Austin TX or Silicon Valley there would be no problem. (I love Fry’s Electronics!) But government is the local industry here and they don’t need local electronics parts stores, just conference rooms.
So, vacation is soon and we’ll test out the system in real life instead of the driveway. And perhaps I’ll get some solar-powered iPhone programming done!

I flew to New Market to visit Shenandoah Avionics Monday to replace the D.G. (aka directional gyroscope or heading indicator). Finally, after a very long backorder, it had come in from Aircraft Spruce. (For symmetry’s sake, there should be a New Market Avionics in Shenandoah airport.)

It was a nice flight down there in the morning. I keep overestimating my airspeed though, I got there later than I’d planned. I pulled up to the unmarked hangar in the middle of the field (the airport owner doesn’t let Shenandoah Avionics put up a sign for some odd reason) and stopped.

When I went inside, the hangar was full, so we’d be working outside today. No problem, it was a pleasant morning. The mechanic and I got started, I removed the panel and loosened the existing DG’s mounting screws. He did the upside-down work from under the panel and dismounted the old one. We found out pretty quickly how it failed. They’d not seen this failure before where the instrument fittings broke. Usually the vanes on the gyro break off apparently.

So, I get to take the old one home to disassemble it. The owner suggested I cut away the case and make a teaching instrument out of it as the rotor was probably in good shape. Sounds like a good idea!

We checked the air and vacuum hoses to see if they were too tight, but they had the right amount of play in them. Sometimes things fail and we won’t be able to figure out why. This is one of those cases. Not all answers are worth the effort.

While the mechanic reached the new instrument up from the bottom, I pulled it into place from the panel and mounted it. Naturally, the mounting screws were different between the two instruments, so we had to put a new hole to the left bottom. The old instrument had the third mounting screw on the right bottom. The nice thing about standards is that there’s so many to choose from.

This new DG has a heading bug. We also wanted an internal light, but I couldn’t find one in our price range that had both. (To have both would have almost doubled the price.) So, the bug was it. My IFR instructors will be pleased, and it will be a lot easier for us owner-pilots when flying too. But the knob for the bug also meant another new hole. The new DG was finally installed (here shown on my flight home, I’m using the bug). We tested it, but it didn’t work. So, check the hoses!

The vacuum-powered gyroscopes work by a vacuum pump pulling filtered air through the gyro housing, which directs that air by vanes on the gyro that spin it up to around 5000 revs/min. The little gauge to the right of the new instrument shows the vacuum pressure. (By the way, the new turn coordinator is to the left, we replaced that after my first IFR lesson in the plane.)

Each manufacturer labels the hose connections in the back of the instrument a bit differently. This, naturally, is subject to misunderstanding. Which is what happened. The filtered air intake was connected to the vacuum and vice versa. Once that was fixed, all was good. We taxied around in a circle and it worked. The mechanic was chagrined but I wasn’t concerned though. Mistakes happen, we’re human. It’s the unchecked and uncaught mistakes that worry me. We were checking and double-checking here.

By now it was the middle of the day and I had a bumpy flight home, not as peaceful as the morning’s flight. The winds were from the north everywhere else around here, but due to the particular pattern of hills around New Market, this airport’s winds were from the south. So, takeoff to the south, give extra space to the hill just off the runway on climbout (easy enough) and turn north, then east to home.

Done. Now I can finish my IFR, and the other owner-pilots can do their flying as needed with the DG working again.