Speaker for the Diodes - July 19th, 2007

Jul. 19th, 2007

05:28 am - QotD

"You know you're a nerd when you look back fondly upon a time in your life when cartesian coordinates were easier than cylindrical or spherical coordinates." -- [info] tdj, 2007-07-02

[No, you know you're a nerd when you hear somebody say something like that and it immediately makes sense on all levels.]

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02:22 pm - Thinking Aloud (electricity)

Okay, it should quickly become obvious that I'm not camping in Enchanted Ground[*] ...

The latest American Science & Surplus catalog arrived in todays snailmail. "Oh, right," I thought, "they sell photovoltaic solar cells! I've been meaning to look up whether it'd be cost effective to get some of those for Pennsic."

Eep! On p.52, a panel rated at 12V/1A that they said they got 19V/750mA out of unloaded ... on sale for $144.50. %wince% Okay, not in the cards for this year, and probably not any of the next several years for me, unless I can find a way to turn it into a profit-generating thang as well as an electricity-generating thang. So looking up whether their shipping could get it to me before I leave or not became moot.

OTOH, they've got a bunch of rechargeable batteries for what looks like good prices so far (i.e., before checking the AH:price ratio of car batteries down the street at Advance Auto Parts): 6V/12AH Pb-acid $7.50, 15ct. "grab bag" assortment of NiCd $3.95, 10 AA NiCd packaged together as 12V/1AH (but easily cut apart to use as individual cells, so maybe I should get these for me DigiCam (but I'd better check the camera's manual to see whether it warns against using NiCd cells)) $5.95, single AA 1.2V/2100mAH NiMH $2.25 (I think those are $13.95 per 4-pack at Rite Aid -- dunno about other local retailers).

The main thing I'm pondering how to run is rated at 5V/2A (I tried four NiCd D-cells and got less than two hours), so either the 6V/12AH Pb battery plus enough solar cells to both recharge the battery and run the device (not cost effective), or a much better idea of how often I'll actually want to be making active use of the device to get a better idea of charge/drain times (not enough info just yet), would be useful. I think the grand plan there will wait a bit longer to get into seriously trying to implement it.

So the secondary concern is wanting to extend the life of the battery+inverter I'll be leeching off of to recharge my PDA and cell phone (and the laptop I borrow, if I do borrow one) and to help me feel less guilty about leeching off of [info] syntonic_comma's battery (I do wish I'd remembered to yank the battery from my car before it was towed). Of course, being able to skip the inverter stage would help ... the catalog list a "7-cell Li-ion pack" with an assortment of connectifiers and output switchable "between 3V/6A up to 8.4V/2A" (I hope they mean there arew a bunch of voltages available in between the two extremes) but it doesn't list an AH rating, which makes it harder to judge the cost-effectiveness ... and neither my phone nor my PDA has a nice, standard, barrel or phone connector for power. (I can charge either directly from 12VDC with a cigarette lighter socket -- easy enough to wire up if I get a chance to swing by a Radio Shack or similar store, or if I find the one I used to use as an extender when I drove a car with a lip on the ash tray that prevented the plug from the phone I was using then from fitting into the lighter.)

Third on the list is powering the digital camera. Not wanting to drain the laptops/phones/PDA master battery for that, especially with inverter losses (wait, just how efficient are those itty bitty consumer-grade 100W inverters these days, anyhow?) I was planning to bring a Big Pile O' Batteries and just run it on alkaline AA cells when the two sets of NiMH cells I have run out. But I wonder: if I can afford to buy a mess of NiMH or Li-ion AA cells in time (and run them all through my charger), will they hold their charge long enough in the camera bag to still do me any good in the second week, or should I stick with alkaline (or maybe NiCd) for Pennsic?

Golly, if only I were going to a party known to be frequented by electronics geeks, scientists, and engineers between now and War! ;-) This sounds like a problem to discuss over ice cream, n'est-ce pas? Gotta remember to take the catalog with me to Baitcon this weekend.

(Whoah. I just noticed a 10-pack of A76 cells -- which suck in film cameras, which prefer S76, but are great in laser pointers -- for $1.50. That's less than a single cell costs at the drug store.)

[*] This footnote grew into a whole entry of its own, about the many different ways of enjoying Pennsic and how I feel about bringing electronics, which I'll post a little later this afternoon.

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03:14 pm - Earworm

I've got the song "Signs" (at least I think that's the title) stuck in my head and I've no idea what put it there today.

The sign said, longhairfreakypeople need not apply
So I tucked my hair up under my hat and I went in to ask them why ...

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