Maybe it is just because I have been doing this kind of stuff since before I was 10 (I actually still have some circuits I built that long ago), but the dangers about lead, toxic materials, etc, seem overblown; at least, I look and feel perfectly healthy today (not a concern here, but I have had more than my share of parts burn and explode, including electrolytic capacitors (the electrolyte is not acidic because for one you don’t want acid on aluminum); I’d only be concerned about things like oil-filled capacitors that don’t have “no PCBs” on them, not that I have ever seen one). Modern electronics are mostly detoxified anyway (look for a RoHS label, which bans lead, mercury and stuff like that, except for special uses like fluorescent lights, which still have restrictions on how much mercury they can contain).
As for shocks from capacitors, that is a definite possibility, but probably not a concern in a VCR unless specific failures occurred, preventing discharge, and it was recently plugged in (most newer ones use a switching power supply, which has a capacitor charged to AC line voltage, otherwise, 20-30 volts max). FWIW, even a CRT TV doesn’t have “deathly” charges in its capacitors (actually the capacitance of the CRT, which is very low, around a few hundred picofarads, less energy (~50 mJ max) that some static shocks (~300 mJ) according to Cecil, but gives you a good shock, as I have gotten before, but certainly nothing that made me think it was deadly, much less end up across the room).
Of course, age is probably the biggest concern here, I think it would be better to wait until grade school (probably when I started going around the neighborhood and picking up discarded electronics, something that I still do today, although I recall that I didn’t start making actual circuits until a bit later but used the parts to make stuff).
Hell, when I was a kid, quite a lot of my toys were fashioned out of pure lead. (I don’t recall sucking on them, though.) I do recall biting down on lead sinkers very frequently, to fix them to my fishing line.
A handsaw is one of the most dangerous non-powered tools. I can’t imagine a child of 5 having the strength, control and judgement to use one safely. I believe children should be allowed to play and take risks, but this strikes me as very unwise.
As for the VCRs, I think the worries about capacitors, toxicity and so on are a distraction. I would be far more worried about injuries from sharp edges, from screwdrivers slipping, and so on. I have more than once sliced my hand open on sharp edges inside a desktop PC, and the skin of my hands is tougher than that of a 5-year-old.
If you gave an adult the job of disassembling VCRs, you would first carry out a risk assessment, and consider whether the job required PPE such as gloves and eye protection. If a child gets injured, your colleagues will have to answer uncomfortable questions about whether they carried out such a risk assessment, and if not, why not.
I don’t think a four-year-old will be proficient enough to use a screw driver on this job. The very FIRST thing a kid will do is stick his/her fingers in the slot. Then anything handy will be jammed in there.
Actual “disassembly” will be either throwing the unit on the floor, bashing it against a table, or beating hell out of it with a Tonka truck.
~VOW
I have a picture of my dad as a 2yo toddler, playing with a 14 inch screwdriver given to him by his dad, probably to encourage him to invent something like his old man did. The pix were taken by mom. How times have changed.
Au contraire. Last week I saw one of the smarter tykes ask for a screwdriver to begin dissection on a fresh unit that had been untouched by other four-year-old hands. The teacher handed him a slothead screwdriver to remove a Philips screw. He stared at the teacher with a look of world-weary contemptuousness and duly informed her that it was the wrong type of screwdriver. It took everything I could muster to keep from leaning over and whispering in his ear “pssst, dude—women.”
How does the school itself feel about these projects? (Handsaws? Really? :eek:)
And one thing I know from my own childhood – kids will always find a way to make something dangerous. (One of my favorite things about being a kid, actually)
It’s not exactly a well-guarded secret. There’s a flyer on the door of the classroom soliciting VCRs from parents. I’m reasonably certain that it hasn’t escaped the director’s notice.
One of the more interesting things I’ve seen around here. But, again – why VCRs? 1/4" open-reel tape drives sound more fun (maybe no to a preschooler) – and probably not any cheaper. One could actually do cool things like splicing tapes &c. if the boxes were made cogent.
I’ve looked into caps and I think I agree that there’s very likely little charge “capacitated” or stored in them for such a low-current, low-V device. I get worried working myself on bigger, 300W power amps with giant electro caps, but I’m old enough to not care/take precautions/discharge stored capacity with a wrench/whatever. Not sure – again, I agree – there’s an issue with capacitance imbricated within a little VCR.
If you’re letting kids use handsaws, the whole safety thing has gone out the window, so I’m not exactly sure what the point is in asking us anything.
You will have someone who cuts themselves. It’s inevitable.
I agree; other than the mechanical assembly that contains belts and gears, there’s not much to be learned from taking apart a VCR. I would suggest taking apart something that is simpler and more electro-mechanical. Like a kitchen mixer, garage door opener, or old sewing machine.
VCRs contain a switched mode power supply (SMPS), and the input caps have about 170 V on them when the VCR is powered. The caps *should *discharge when power is removed, but I wouldn’t bet my life on it. (The exception is if the VCR hasn’t been powered for a *long *time, in which case it can be safely assumed the caps are discharged.) To ensure the input caps in the SMPS are discharged, short the two prongs on the AC plug together using jumper wires, and then measure the voltage across the caps using a voltmeter.
This pretty much. I’m usually pretty gung ho about letting kids get involved with mechanical stuff but letting PRE-SCHOOLERS attack a VCR with flat blade and phillips heads screwdrivers? You’re begging for a really nasty accident re cuts from sharp stamped metal frame edges or someone losing an eye or gouged hands when your attention is diverted elsewhere.
This makes no sense; there is a bridge rectifier at the input to rectify the AC voltage and it prevents current from flowing backwards (or it wouldn’t be a rectifier) so there should be no voltage present at the plug (the rectifier could short, but then there wouldn’t be any capacitor left, assuming the fuse didn’t blow first).
Well, if you read the OP, you would know that I was under the misguided impression that any capacitor of any size = instant mumble mumble style death ray = early dirt nap. I was oh so woefully wrong, and my misconception was benevolently rectified. A saw, however, = big bloody ouchie, but nobody is going to die (we hid the Big Book of Magic Tricks just to be on the safe side). I felt that the distinction was sufficiently large enough to justify the interrogatory.
Well I also went through the dissassembly phase as a kid, and I certainly sliced my hands up plenty of times, and I think you are seriously underestimating how easy it is to injure yourself badly with simple tools if you don’t know what you are doing.
The problem is that a lot of the components will be machine assembled and kids aren’t going to have the strength, dexterity, and experience to dissassemble them safely, especially when they start getting frustrated with how tightly everything is fastened together.
Best case scenario you will end up with a class of kids with scratched and cut up hands, worst case scenario one of them opens an artery with a saw or loses an eye when they try to lever something apart with a screwdriver
Chances are that some of them will start taking things apart at home, and I can’t see any real educational benefit in learning that electrical items are full of small sharp things.
I mean, they will have fun. but they’d probably have fun if you handed them all a box of matches too.
I’m having trouble seeing what makes this worth taking the risk.
