Archive for February, 2016

Build This Idea: Better DC Power

Wednesday, February 17th, 2016

A significant amount of my home plug use – if not outright electricity use – is for electronics. When travelling, various electronics are the only reason I need to bring plug adapters.

(Point-and-shoot and SLR cameras are particularly bad, usually requiring proprietary chargers that don’t even charge all that fast.)

For a brief moment late last century, you could travel with no chargers, and just buy more AAs wherever you went. Or use a local charger with rechargeable AAs from anywhere. A Walkman would run on American AAs as well as on European AAs.

The Nexus 5 has a 8.7 Wh battery, a lot bigger than 0.6 to 3.9 Wh in an AA battery. But there’s problems.

Phones, tablets, laptops, various camera chargers all ultimately use low-voltage and fairly low-power DC. Using wall-warts from to 220 V AC is just asking for waste. Using incompatible power adapters for many devices is insanity.

USB sort of solves this, but comes with its own problems. Using the same plug for data and power is going to end up like CD autorun did in the 1990s: helpful but dangerous. Plugging into an unknown charger — or an unknown cable — is a risk now. You couldn’t get your Walkman rooted by a AA battery. (You could conceivably get a device fried by a rogue battery, but that’s a one-time loss, not an ongoing pwnage.)

You can now get USB cables with a switch to disconnect data pins, or with data pins unconnected, but that means you’re carrying your own cable. Android has an OS-level data switch, but I am less than confident of many manufacturers’ ability to not get low-level firmware pwned, so a phone-based low-level physical switch would be appreciated. Still, these are hacks: better make sure not to switch by accident.

USB Type C gives more power, which will come in handy for bigger devices. At some point you have to ask why put data pins on something you’d ideally plug in everywhere, why require trusting the chargers? I can only hope it is a stop-gap until better wireless power is possible. (Just make sure you can’t get rooted over the air!)

Still, the installed base means that working with various kinds of USB (type A and micro-B in particular) is probably our best bet — and maybe at some point we’ll get hardware with a physical data pins switch. So: power pins on the 5 V DC USB plug for everything!

Canon and Nikon, I’m looking at you.

Bonus: photovoltaics

Photovoltaic/solar panels generate intermittent DC electricity. That is a very interesting fit with electronics. Traditionally a big problem with using solar power is storing energy for when it’s dark. Many electronics have batteries that can store the energy for several days, and using DC eliminates AC/DC conversions.

It would be a neat project to put a PV panel on the top lid of a laptop. The top of a 15″ laptop is about 0.10 square meters and could collect about 15 to 30 watts (around 45 degrees latitude, with today’s mid-efficiency panels). That’s not as much as a AC power brick — for bigger laptops, these are usually rated 50-70 watt — but it’ll top up a laptop nicely. Plus, a deep purple/black PV panel would look very nice on a black laptop. Novena case, anyone?

One thing to note is that you’d have to make sure things don’t melt. Consumer electronics aren’t usually designed with being left in midday sun in mind.

PV panels on phones would be a tougher sell due to smaller size and therefore energy potential, and things like SLR camera battery chargers are ill-suited. Perhaps it would be better to have one PV panel with a thin battery, and running everything off a common charging standard. These exist for USB but efficiency is iffy and design is often uninspiring.

Even if these aren’t commercially viable for mainstream products, I would love to see them as aftermarket or hobby mods: a replacement lid for a Thinkpad, or a flat, e-reader-size USB power bank with a PV panel on top.