Dan's Data letters #140
Publication date: 3-Feb-2005.Last modified 03-Dec-2011.
Cold Heat continued
In your last Lettuce column, you mentioned the Cold Heat soldering tool.
I thought you knew 99% of Everything, but, from the sounds of it, you don't know the secret of the tool.
The tip is made from a graphite-like electrically conductive material, built in two halves, electrically isolated from each other.
Current is passed into the joint, almost instantly making it hot enough for conventional-alloy solders. As you know, graphite (unlike certain other carbon allotropes) has relatively poor thermal conductivity, so the tip stays cool.
It is more of a pain to use than a real iron.
The iron itself is just battery compartment, switch, LEDs, tip retention mechanism and little else.
It's also got the coolest case of any soldering tool I've ever seen. And you can use it as a torch, with the white LED in the tip.
Luke
Answer:
You, and the several other people who sent me similar e-mails, are quite right; the Cold Heat is indeed a resistance
soldering iron.
Resistance soldering's been around for a long time, though nobody made a small mass-market version before the Cold Heat, as far as I know. Simple resistance soldering outfits are popular with model train people and related hobby metalworkers, and there are big commercial models that can handle all sorts of jobs if you get the right "iron" and the right transformer to power it - AA-battery products need not apply.
Resistance soldering for electronic components can be a bad idea. Apart from the fact that it's impossible for simple resistance irons to control the temperature of the joint (hence the track-lifting problems some people experience), it's also possible to fry components if you accidentally bridge two board contacts or IC pins with the iron tip, without any solder, and thus apply the soldering voltage to the component(s). If there's little enough resistance between the points you've bridged, pop. That said, though, you apparently can use it effectively for electronic work, if you know what you're doing.
To do quite heavy duty resistance soldering without a special iron, you can use a soldering gun without a tip.
Step 1: Rent bulldozer
I have no ability to get broadband where I live, I am on another exchange than the one that the ISP that delivers ADSL has setup a DSLAM at. A friend 5km away though the forest is on the correct exchange though, and has a nice 8mbps ADSL connection.
My hope was to run a wireless link to him. I found WiFi PLUS, who claim that their products are so very amazing...
Are they just plain lying, or is there some truth to it?
should I just find myself an old parabolic dish and build something?
The forest does have some tress that are higher than where I will be able to set up the antenna, but there should not be any mountains between our houses, according to an elevation map, and we should also be at the same elevation.
I live in Sweden where the max output is 100mW, but I have no problem with exceeding that limit ;-) Just the fact that I'll have to buy myself an amp ;-)
Per
Answer:
I don't know how believable WiFi PLUS's claims are. There's close to no information, pro or con, about their products
on the Web, and I've never even clapped eyes on one in person.
Their parent company is Niljon, who sell similarly promoted antennas for lower frequency radio. They don't exist in quite so hard an information vacuum; see here for a favourable (but sponsored...) review of one of their products.
So it's quite possible that WiFi PLUS's claims about their antennas (basically that they offer about twice the performance you'd expect from their raw gain figure, in situations where the signal has to pass obstructions) could be true. I'm quite willing to give them the benefit of the doubt.
But for five kilometres through trees, you're likely to really be up against it. Trees are good at soaking up 2.4GHz, and the greener and damper they are, the worse the situation gets. With amplification, Wifi-Plus claim that their fancier antennas can do better than five miles through "moderate" trees, and they also say that a couple of their bigger antennas should work OK through "dense" trees as long as you don't even want half a kilometre of throw, but it all depends on how dense and green the trees are, and on the relative elevation of the antennas; the further off the ground you can get the antennas, the better.
Even if these antennas are exactly as good as Wifi-Plus say they are, they're not magic. Without giant masts and amplification, I wouldn't be surprised if you got a signal when the trees were reasonably sparse, and deciduous, and leafless, then lost it again in the spring (and during rainstorms), despite having spent several hundred US dollars on the hardware and considerable time and effort aiming the antennas.
Since WiMAX is just around the corner, you may find you can get good wireless broadband pretty soon anyway, without having to depend on all this gear.
From the cheap seats
Is there any way to connect a DVD player to a TV which only has an aerial coax socket on the back? I previously tried to run one through my VCR's three unused composite video connectors, but this apparently activated the Macrovision copy protection circuit in the VCR and distorted the picture. I was thinking of running a 3 to 1 composite video to RF coax jack into the TV, and then the antenna lead from the VCR into a double adapter into the TV. This should bypass the Macrovision circuit. After all I only want to watch, not tape, DVDs.
Michael
Answer:
To do what you want to do, you can use an RF
modulator. They have passthrough antenna connections,
so you just plug them in-line with the antenna cable going to the TV, and then set a channel for the modulated video,
the same as you do with your VCR.
The image quality from this won't, of course, be fabulous.
It's the DVD player that applies the Macrovision distortion to the signal coming out of it; the VCR just falls victim to it. Macrovision is turned on by most commercial DVDs, but you can disable it on many cheap DVD players these days, one way or another. The better cheapo players come with Macrovision (and region coding) turned off.
Head-amp grunt
Do you think it would be possible to use this high powered USB card to power the BitHead headphone amp without having to use batteries, and still get full quality?
It's a shame those BitHeads can't be powered by an AC adapter or something.
Micah
Answer:
Not likely; the limiting factor is voltage, not current. Four AA alkalines give the amp a nominal six volts, but the
BitHead will run from them for about 30 hours; that's an average current draw of 40 milliamps, tops, which is unlikely
to ever spike beyond a couple of hundred milliamps. USB gives only five volts, and it's that which limits the amp's
headroom.
That Parvus widget is also not, of course, an expansion card for a PC; it's a PC/104 board for embedded systems. You could probably hook it up to a PC's PCI bus with nothing more than a couple of connector adapters, though; PC/104-plus devices like this are just regular PCI in a different shape, as far as I know.
You could, also, run a BitHead from an AC adapter - you could probably just hook up a 6V regulated adapter to the battery contacts with alligator clips. Or do the same thing with a 6V lantern battery, for _monster_ battery life (the nominal capacity of an alkaline lantern battery is more than 20 times that of a set of four AAAs), and no possibility of hum problems.
Not, of course, that you have to use battery power; I notice no difference in the sound for normal listening volume when running my BitHead(s) from USB power. It's only when you wind it up and the clipping light starts flashing that you actually need the extra volt.
Light advice
After hours of rummaging through Google for some sort of instructions on wiring my own chase lights (I own a theatre company and we're doing a Cabaret-style show), I've been wracking my brain trying to think of somewhere I can get some help.
With all the electronics knowledge you have dispensed to all of us unwashed, I thought maybe you could point me to a page somewhere that could break it down for me. I know I could purchase something for US$100 or so, but I enjoy doing these things and it might save me some money if I do it myself.
Rob
Answer:
The basic circuit involved isn't very complex; see "120VAC Lamp Chaser"
here, for instance. Three amp relays
would let you run a big ol' string of little fairy lights off each channel, and three channels is enough for a plain
chaser effect.
If you're doing it yourself, though, it might be a good idea to run the lights from a 12 or 24V transformer. You'll need higher current relays then, but you'll be able to use off-the-shelf garden-light lamp strings, which are cheap, and a rigger who puts a nail through the string isn't going to turn himself into a crispy critter.
Killer cells
I'm hoping you might be able to help me understand whether I fried my Sony DSC-U20 digital camera by substituting alkaline batteries for the included NiMH rechargeables.
I bought the DSC-U20 specifically because it ran on two AAA-sized NiMH rechargeables. When on holiday, I would use the rechargeables until they ran out, then reload the camera with standard alkaline AAA batteries. That let me travel without the charger.
At 13 months after purchase (yes, right after the warranty ran out) the camera started chewing through batteries at a prodigious rate. Like, 3 minutes from new to flat. I suspected that the flash capacitor was somehow shorted out (the flash charging LED flashed continuously) but that is just my wild-ass uneducated guess.
Sony kindly (after much complaining on my part) repaired the camera under warranty. It worked fine for another 3-4 months, at which point it failed again in the same manner (batteries fail almost immediately). Again, I was using mostly alkalines instead of the rechargeable NiMH (well, truth be told, my wife accidentally threw away the rechargeables, so by this time I was using exclusively alkalines).
Given that alkalines put out 1.5v each vs. the required 2.4v listed on the bottom of the camera, is there any chance that I somehow fried the camera by using the alkalines instead of the rechargeables?
In the interest of continuing to use the (proprietary) Memory Stick I already have, I'm inclined to buy a cheap DSC-U30 rather than spend $US300 for a new small format point-n-shoot digital camera + $US75 for a large capacity card. However, I don't want to do it if I'll just fry the camera again!
Can you help me understand if I was just the victim of a "lemon" camera, or if I somehow damaged the camera?
John
Answer:
The batteries probably had nothing to do with it. Yes, the nominal voltage of alkalines is higher than the nominal
voltage of rechargeables, but that seldom makes a difference to anything. When freshly charged, NiMH rechargeables
can easily manage 1.4 volts per cell (which drops off quickly as you suck out the first couple of per cent of the
cell capacity; it'll also sag back down to about 1.2V if you just leave the cells alone for a few hours). And, under
heavy load (like, pretty much any camera, especially if it's got a flash), alkalines will sag down towards or even
below 1.2V/cell. This load level isn't good for an alkaline cell, and means it will probably deliver lousy run time.
Modern digital cameras are much less mean to their batteries than were digicams from a few years ago, though; alkalines
in a lot of older digicams may deliver fewer than ten flash pictures (which is why I wrote
this).
Anyway, what all this means is that devices made to run from AA or AAA cells, including cameras, are generally quite happy with alkalines or rechargeables; 1.7V-nominal lithium AA cells can cause problems in some cases, but even they're safe for pretty much everything but flashlights. Perhaps the U20 has some issue in this regard that I don't know about, but I think you've got a different problem.
T-Rex suit pending
I must admit I have a guilty pleasure.
Every few days I check your site for new letters (that's not the guilty part) hoping beyond hope that someone has emailed you about another overpriced perfect sounding power cable or free energy device. I feel guilty about it, but I can't deny that I love it when you verbally stomp all over them.
You may have heard about the bear suit guy, Troy Hurtubise. After watching Robocop and getting mauled by a bear (not necessarily in that order) he was inspired to build a protective suit. It's even been on The Simpsons.
He's also invented a "physics-defying substance which he claims eliminates the cross-transfer of heat and prevents anything coated in the substance from burning up."
Recently it was reported that this same inventor again defied all known rules of physics and created something that can see through walls. The French, scientists and a former instructor from MIT, and the former head of Saudi counter-intelligence are all involved!
Jason
Answer:
Troy Hurtubise
walks
the
slow,
heavily
armoured
walk, as well as talking the talk. He is clearly Not
Like Other Men, both physically and mentally, and hell, maybe he's actually done what he says he's done with this
magnificent new ray-gun of his, despite widespread
derision.
I will not be even slightly surprised if the thing turns out not to work, though. He's made bold claims before that haven't (yet) panned out.
Mi toknogutim
Dans, Tolong review tentang Intel Deluxe Pc Camera. Webcam ni beshh!! Murah, hanya RM100.00 @ aaaa..US30.00 Saya kno u like to review cheep webcam inn yor website. I hop u review dis webcam.
Intan
Answer:
Pidgin. People are sending me mail in Pidgin now.
Do I need to specifically forbid the use of languages that sound a bit like English?
(A reader has now pointed out to me that this looks more like rather badly spelled Bahasa Melayu. It also resembles Indonesian, but "RM" stands for Ringgit Malaysia. That doesn't explain the English-ish bits, though, since neither Indonesian nor Malaysian creoles have much, or any, English in them.)
