Dan's Data letters #159
Publication date: 24 January 2006.Last modified 03-Dec-2011.
Mmmm, salad...
Could you build LED grow lights like these or these yourself, with common red/green/blue LED diodes?
Freax
Answer:
Simple LED arrays with current limiting resistors rather than fancy driver hardware, all running from reasonably efficient
power supplies (not hard to find these days - old PC PSUs will do it, though dedicated single-voltage switchmode boxes
would be better), won't be terribly less efficient than the fancy commercial LED grow-lights. If you want to build
an array big enough to light more than a science-fair quantity of plants, though, it still won't be cheap.
My first thought on receiving your e-mail was that even arrays of high power LEDs - hordes of 5mm units, or roughly
a tenth as many one watt super-LEDs - wouldn't deliver nearly enough light to compete with traditional super-high-intensity
HID and high pressure sodium vapour lights (plus
compact fluorescents, for some applications; fluoros
with weird output spectra are now apparently gaining some popularity). Those are what people normally use to grow
a decent crop of marijuana tomatoes indoors.
Then I thought again, when I realised that while fluorescent and short-arc lights have excellent luminous efficiency
(easily beating the best current white LEDs), a lot of their output is wasted if you point them at plants.
Weed lettuce is green because it reflects green light; plants don't actually have much use for the green
portion of the spectrum, so lights that emit it aren't necessary. Exactly which
portions
of the visible spectrum are useful to a given plant depends on the plant and on what stage of its life cycle it's
in, but generally speaking, you can get away with using nothing but red light. Red plus some high spectrum (blue and
violet) may give you better growth, red plus some mid spectrum (orange to green) may give you better flowering (of
particular interest to people who are attempting to propagate kind bud orchids), but even if you
give 'em nothing but red, pretty much all plants will do passably well.
So a bunch of red LEDs actually do make a good grow-light, especially on a power-consumption-per-ouncestrawberry
basis. Coloured LEDs have only moderate luminous efficiency for general illumination purposes, but when you only care
about a few narrow frequency bands - for growing plants, or illuminating traffic lights, say - they beat the heck
out of the competition, watt-for-watt.
Dollar-for-dollar, though, things are less clear.
The basic 22 watt "Starter kit" from LED Grow Lights sells
for three hundred US dollars and covers a maximum of... three square feet. Bigger setups cost less per unit area,
of course, but an 800 watt mixed metal halide and sodium vapour setup from an ordinary growlight joint
retailer only costs $US450 or so, and will cover a square about five feet on a side.
So. Little LED setup uses 7.3 watts per square foot, and costs a hundred bucks per square foot. Say 75 bucks, for a bigger rig. The not-terribly-big traditional system uses 32 watts per square foot, but only costs seventeen bucks per square foot.
It's going to take some pretty lengthy growth periods for the savings on your electricity and bulb-replacement bills to come close to making up that kind of difference.
Assuming you're running a 25 square foot system and paying 15 US cents per kilowatt-hour for power, it'll cost you $US450 up front for the 800 watt traditional system, which'll then cost you $US2.88 a day for power, if it's on all the time. It'll actually only be on around two thirds of the time, on average, depending on whether you're forcing your plants to grow or tricking them into flowering. So that's more like $US1.92 a day.
The LED alternative will only draw around 183 watts, and therefore only cost you around 66 cents an always-on day for power, or 44 cents for average cycles. But it'll cost you something in the order of $US1875 to buy.
Taking bulb replacement into account, the LED alternative may let you break even in less than two years. Whoopee.
The lower wattage of LEDs will, however, let you light a larger area of ganja cabbages before
your house starts drawing so much current and showing up so brightly in police night-time far-infrared-camera sweeps
that some uniformed gentlemen call on you for a friendly inspection of your operation. This inspection may, in certain
circumstances, result in fines and/or imprisonment of sufficient magnitude and/or duration as to outweigh a very considerable
initial outlay, and so that may well factor into your calculations regarding how worthwhile LED illumination is.
So, if you can really save some money by building your own LED growlights, it could definitely be worth doing.
For 183 watts worth of homebuilt arrays, though, assuming you're using a bunch of Luxeon IIIs and running them at their rated power for maximum life (you can wind them up to considerably more with enough cooling, but I wouldn't want to run them for months on end that way), you'll need 61 LEDs. At a shade over 16 bucks US per LED, that's $US976 (less volume discount) for the LEDs alone. Spend the time to assemble the things into a lamp and add the power supply and the bargain gets even less exciting.
The LED Grow Lights products use 5mm LEDs, which are much more difficult to heat-sink than Luxeon Stars and so
really can't be pushed to more than a tenth of a watt each without severely impacting their lifespan, but are still
considerably cheaper. You may only have to pay $US250 or so for the 1800-plus quality LEDs needed for a 180-watt-ish
setup. But you'll be spending the rest of your existence as a corporeal being soldering the darn things onto their
array boards and testing the result. You can forget about getting high on the dopebeer made from
the hops you're growing; the solder fumes'll get you first.
So, in brief: Yes, Do-It-Yourselfing such a project is possible, and the result will probably work fine. But unless you only need a little tiny growing area, it may still be a more expensive and/or annoying project than you're willing to undertake.
X-Filesify your house
I'm pondering doing some el-cheapo portrait photography (just for the heck of it, not paid!), and think it would be fun to play with smoke and bubble machines in combination with portraits!
Heck, if I'm wrong at least it'll give the spare models (friends) something to do while I'm taking pics of somebody else.
Much to my disgust they seem to be fairly expensive. Do you have anything in your bag of tricks that would either 1. let me find one cheaply (doesn't need to be particularly good), or 2. let me hack one together myself, in the grand tradition of all things cheap and nasty?
Danny
Answer:
I'll cut to the chase here, because it's highly entertaining and I feel dreadfully clever for just now working it
out.
Use a steam iron.
Fill the iron with smoke fluid instead of water, set it to steam and the lowest heat that turns out to work, and hey presto; smoke comes out every time you tip the iron level (or hit the shot-of-steam button, if you've got a fancier iron). It's hardly the directed flow of a proper smoke machine (the smoke will head pretty directly for the ceiling, though you could kick it around with a fan), but you can't beat the price of a second hand steam iron, or indeed the $0 you'll pay for an iron you already own. There'll be no damage to the iron, either, as long as you treat it like a regular smoke machine - clean it by blowing some distilled or deionised water through it every now and then.
The fluid we're talking about here is the water-and-glycol stuff, not the fluid used by oil atomising "haze" machines (a.k.a. "oil crackers"), which produce toxic smoke, though not as toxic as the smoke from the hot oil hazers they replaced.
(I'm not sure whether a steam iron full of oil would work better as an interrogation or an incendiary device).
Water-based-fluid smoke machines all work basically the same way. The fluid's sucked out of a reservoir by a pump that pushes it through a tube that's heated by an element. The fluid vaporises and shoots out of the nozzle; when it re-condenses into tiny droplets (a few centimetres from the nozzle, at most), it's smoke.
Anything that vaporises the fluid will make smoke. Drip smoke fluid onto an electric hotplate, for instance, and it smokes.
Smoke machines let you shoot the smoke in a particular direction, and easily control its production, but any well-past-boiling object can be pressed into service to perform the basic function.
The cheaper commercial smoke machines - the cheapest of them are well under $US100 these days - are generally non-serviceable; you can't take them apart to fix them. They may work fine for occasional use, but if the heater element burns out or the pump motor dies, or if you just blow too much fluid through without cleaning the pipe and jam it, you have to buy a new one.
The more expensive machines are serviceable, and often have a higher flow rate too, plus niceties like variable power and so on. But, basically, they're all the same, and it really wouldn't be terribly hard to make one. Copper tubing, windshield washer motor, old electric iron/toaster/whatever, electrical and thermal insulation material (most smoke machines keep their heater assembly inside a block of ordinary fibreglass insulation). It ain't rocket science.
It also isn't the work of a moment, though. So if you value your time, a $US100-delivered machine from eBay or wherever could be a better idea for frequent smoke production.
In the meantime, I can strongly recommend a humble steam iron. Just make sure it's been converted back from Rave Mode if someone wants to press a few shirts.
Try eating them
I am moving house and trying to get rid of a big pile of old VHS tapes and magazine cover CDs, etc. There seem to be some places that will recycle this kind of stuff overseas. However, I can't find anywhere in Australia. I would even pay postage if I could figure out where they should go.
Any ideas?
Michael
Answer:
As far as I can see, these things are unrecyclable in Australia.
Not that this is necessarily a huge environmental disaster. The amount of oil that goes to plastics manufacturing is insignificant compared with the amount we just plain burn, and if vast advances are made in recycling technology, people can just go back and mine our landfills. The fact that plastics don't break down is, in that situation, a plus. And despite the endless NIMBY arguments about landfills and the ghastly substances that can leak out of them, it's not as if the world is ever going to run out of big holes in the ground. I don't think a plastics-only landfill would be much of an environmental problem at all - well, not unless it leaked Phthalate Death Soup or caught fire, anyway.
The reason for the unrecyclability of video tapes (in particular) and CDs is that they're made from mixed materials, so they can't just be sorted into a bin, shredded and remelted. Generally speaking, mixed plastics melted together give a useless result, and surprisingly small amounts of Plastic B can ruin a whole vat full of Plastic A, thanks to the low entropy of mixing of long molecules. Some substances are recycled by just shredding them in bulk, but the result isn't useful for many purposes - shredded tyres can be a useful additive for road bitumen, for example, but there aren't many such applications for mixed plastics.
So different plastics have to be separated out, which is hardly a simple process for some mixed items. Video tapes are screwed together, for instance; a machine could easily enough separate the halves, extract the other metal parts and discard the spools, tape and front gate, but I don't know whether anybody's come up with an economical way to do that yet; most recycling separator systems start by pulverising the incoming material, then try to separate the confetti.
Since tape cases are, as far as I know, made from dirt cheap black polystyrene, there's not a lot of value there to be recovered.
This could explain why places that "recycle" video tapes actually remanufacture them; erasing the better tapes for reuse, and putting new tape in the shells of the lower quality ones, no doubt makes it a lot easier to turn a profit. Reduce, reuse, recycle is an order of preference as well as a catchphrase.
There are CD reprocessing systems that shred the discs, then separate the fragments of the label-side epoxy layer and the thin metal layer from the polycarbonate that makes up most of each disc. It's possible that minor contamination with epoxy and aluminium won't hurt the polycarbonate's quality too much, since they're not thermoplastics; aluminium, in particular, definitely wouldn't screw up a polycarbonate melt.
But despite AOL's best efforts, there just aren't that many CDs out there to recycle. They're not like PET and glass bottles, recycling of which gives a lot of economy of scale.
The exact economics of recycling in various countries are shrouded by Byzantine layers of subsidy, rebate and public relations, but I think it's pretty safe to say that it's a business that often can't survive without subsidies - at least, not yet. That, as much as technological issues, is why you often find that Substance X can't be recycled in one or another country.
Bring the noise (with you)
I need a guitar amp with good sound, that's good for outdoor use, and cool looking!
The PyP-Bomb looks good. They're selling it at ThinkGeek.
I would really appreciate your sage opinion on:
- if the specs are OK (sound specs were never my forte)
- if there is an equivalent product available here in Australia... 'cause I have looked and can't see it for sale in Oz.Myles
Answer:
I've no idea if the PyP-bOmB actually sounds great, though it
could be OK for its size.
I bristle somewhat at paying this kind of money - even ThinkGeek's current special $US125 price - for what looks like some eBay dude's made-in-a-garage product, though. (You could probably still get it a bit cheaper elsewhere - ThinkGeek always charge a premium, though their service is top class.) If you totally love the look of the thing then sure, no problem, but personally, I'd go traditional and buy a Pignose instead.
The Pignose is only three watts, but it's got a five inch speaker instead of the Pyp-Bomb's four incher; that'll probably make it more efficient, and you can run it with the box open for more volume (and less bass). At a guess, I'd say the Pyp probably sounds about twice as loud as the Pignose. But the Pignose looks, in my opinion, far cooler.
The Pyp has a 1/8th inch line level socket as well as its guitar socket, but I know from personal experience that the Pignose works OK from line level input; you just have to adapt the plug from your MP3 player or whatever.
The Pignose sells online for $US75 or so. That's batteries-not-included; it uses six AAs, or you can hack a bigger pack onto it for longer run time. It'd be trivial to adapt it to run from standard R/C car stick packs, for instance.
There are lots of other small battery powered amps out there, though. Any half-decent music store should have at least a couple. I bought my Pignose from Venue Music quite a lot of years ago; I don't particularly recommend them, but their prices are decent. They don't seem to stock the Pignose any more, but would probably know who does.
If you want a high-class alternative, the Fender AmpCan is very good, but not cheap.
This thing is as stupid as it looks, but this could be an idea.
A not-too-crazy alternative: Just buy a basic "practice" amp - which'll be louder, and probably sound quite a bit better, than any of the small portables - and run it, when you're away from mains power, from a 12V pack of some description and a small inverter. You can get 150W-rated switchmode inverters that cost $AU50 and weigh about a pound, now; they'll run a quite beefy amp, but may cause it to hum. I don't know, but someone at Jaycar would.
Sinewave inverters definitely won't cause amp (or motor) hum, but cost about $AU200 for a 150W unit, and weigh rather more too.
Still, though, if you can get away with a cheap inverter and a normal 7Ah 12V "brick" sealed lead acid battery, the whole power supply kit will fit comfortably (once you put some padding around the very dense battery...) in a small backpack with room to spare, and cost you little more than $AU100 including a wall-wart overnight charger for the battery. Total weight around three kilos, and you wouldn't look like a One Man Modular Synth Band fresh from Burning Man; you'd just have one cable coming out of the backpack.
This rig could also, of course, run all sorts of other small mains powered devices. A 100 watt load through an inverter will drain a single 7Ah brick in about 45 minutes, but you could run a Pentium M laptop for five hours.
The Total Nerd Option here is to use a one-box uninterruptible power supply to do this same thing. Obviously, you're not going to be doing this with a 5000VA piece of enterprise hardware, and you also need a UPS that can be told not to go BEEP BEEP BEEP when there's no mains power - but you can get Suspiciously Cheap UPSes on eBay for something like $AU89 plus delivery. I bought one a while ago just to see if it was made out of coconut husks and saliva or something, but it hasn't burned the house down yet, and yes, you can shut it up.
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