Hello, my favorite people on the planet! I’m looking for ideas again, namely- if I were to have my students dissect a broken electronic device, which would be the best item to dissect?
I have 6/7/8 graders, and am planning on using the dissection to teach scientific method, how to write a lab report, theorizing… things like that. I also have mostly boys, if that weighs in. So what do you think? VCRs? Toasters? Old cell phones? Also, I’m fairly non-technologically minded, so are their devices I should avoid for safety’s sake?
Something that makes noise, such as a simple electronic keyboard - ideally an older one with plenty of discrete components, rather than just one or two specialised ICs.
Reason for suggestions: Circuit Bending. You do probably need a device that is at least partly functional at the outset though, but you can probably pick something up dirt cheap in a charity shop or flea market.
I taught a computer class to some “gifted” 3rd graders last year, and at the end of the term we took a hammer and pliers to an old PC, keyboard, disk drives and all. The prize was the CPU, but everyone got to take home a chunk. I heard later that kids were brandishing their pieces all around the school and trading them. Not sure how much they learned, but they were only 8-9 years old.
I would suggest something much simpler than a keyboard, phone, or VCR. They are all mechanically and/or electronically very complicated and beyond what 6/7/8 graders are likely to be able to get their heads around at all or at least in the time you have available. Parculary if you are not technologically minded in the first place.
Toasters are probably quite a good idea. The basic function is quite easy (just a heating element) but at the same time they have some sort of little variable timer circuit, which adds some interest. They are also big and simple and easy to get into (unlike say a phone which hard to get into and has components packed into it far tighter than sardines in a can).
A toaster isn’t going to be dangerous unless it’s plugged in and I’m sure you weren’t planning on the item being plugged in. Actually, I’d cut the cords off as soon as you get the items so no one can do anything seriously stupid.
I was talking to my SO about this question, and we agreed that something like a toaster would be a good idea. Your students are going to have a pretty good idea of what one does, but probably little idea how. Maybe go with a couple of different models, so that each one isn’t exactly the same. (Yuck, I got the crayfish full of EGGS, what did you get?)
You might even be able to find a fine selection at your local Salvation Army store.
Besides toasters, other kitchen appliances would seem to be good choices – mixers, blenders, etc:
[ul]
[li]Generally fairly simple electronically, so understandable by kids[/li][li]big enough to dissect easily, and parts are obvious[/li][li]Parts are big enough to see, and explain function (unlike complicated electronics, which aren’t really much to see)[/li][li]supplies are cheap, & readily available (Goodwill, etc. – might not even need to be working)[/li][/ul]
Some of them might be interesting if you obtain old vs. new specimens. For example, an old blender with mechanical switches & 2 or 3 speeds, vs. a newer one with an electronic motor control with many speeds. Can show how design has changed over the years.
I’d suggest an old radio. Tube type would be best or an old 9 transistor radio.
Tube radios used point to point wiring. You can trace the wiring from the plug to the tubes. Show them the capacitors, resistors, and the 5 tubes. Wiki will explain what each tube does.
If you use a transistor radio get a table model. So it’s big enough to trace the foil patterns on the circuit board. show them the capacitors, resistors, and the 9 transistors.
I would advise only older models though, because one problem mentioned often is that in the past decades, with cheap models made in Asia, most are completly non-repairable because the whole outer shell is plastic fused together, no screw holes anywhere. (Because with modern production, it’s cheaper to buy a new one for 20-30$ every several years instead of spending +40$ on the man-hours to get it repaired, esp. if the components are too cheap to make repairing it worthwhile in the first place. Obviously, this is a very bad strategy from a raw resources standpoint, doubly so if the broken units end up in general trash = burned or landfills instead of recycling the important metals).
Related: do you have a workshop in your school with soldering irons etc.? Because at our local alternative festival Tollwood, there’s a guy who sells little stick figures made from computer parts (resistors…) and soldered together. Very nice. So if you have appropriate parts left over after dissecting, the kids could take them next door for the next lesson in metal craft.
It really doesn’t matter; just about any electrical/electronic appliance will do. Examples include old CPUs, hairdryers, toasters, microwave ovens, radios, etc.
Some things to think about:
Cut off the power cords. This will (obviously) prevent someone from attempting to power up the appliances. Don’t forget to discard the (now removed) power cords, as someone might try to plug them into a receptacle.
Make sure they wash their hands afterwards, as solder contains a lot of lead.
Do not take apart anything containing a CRT, such as an old TV or computer monitor.
Even a modern drive has the advantage that the basic components are easily observed, and the functionality of those components has remained the same for decades.
Once the basic functions are worked out you can proceed with a very simple analysis of the performance constraints, something that should be neatly within the capability of your students.
There are a lot of features of a disk drive that can have interesting questions asked of, for example:
[ul]
[li]why are the platters so shiny?[/li][li]why is there a little vent hole?[/li][li]how do the heads avoid scratching the platter?[/li][li]how do the heads move?[/li][li]what has to happen to read data?[/li][li]how long does it take to read a random location on the disk?[/li][li]can more than one platter be read or written at once? (tricky one that)[/li][li]what determines how fast data can be read or written?[/li][li]what are the platters made of? why?[/li][li]how might a disk fail?[/li][/ul]
A real prize would be a set of older disk drives of significantly larger size, and often rather more agricultural technology.
The problem with many electronic devices is that they basically look the same on the inside. A circuit board covered in small components. It takes some experience to work out what a device is nowadays. Usually done in part by looking up the part numbers. Lots of otherwise identical black boxes soldered to a board isn’t going to be much fun to examine.
Very good safety points. Most modern electronics don’t use lead based solder, but you’re going to be dealing with older stuff.
I actually came by to mention #3 - old CRTs have a large capacitance, which means they hold an electric charge for a long time. If you don’t know how to properly discharge one, it can cause injury.
Also be careful of A/C thermostats - they contain mercury.
Please have a plan with what to do with the remnants. My area has electronics and hazardous material recycling and disposal…you should be able to find something similar.
All that being said - I think it’s a great idea. Have fun with it!
-D/a
I agree… I would probably stay away from modern electronic marvels. after disassembly, all they will find is a PCB containing tiny surface mount components. Nothing too exciting there. The best devices would be electro-mechanical in nature, like toasters, hair dryers, electric tools (e.g. hand drills), etc. Basically, anything with a motor or solenoid in it.
I second this. When I was in 6th grade, we got wire, lightbulbs, switches, batteries and such, and were told to build something. I “invented” what I called an “electromagnetic switch”. I didn’t realize until later that I had merely reinvented the relay. The things Crafter_Man suggested are exactly in that knowledge/experience range.
As a long time tinkerer and a lover of taking things apart, I’d stay away from something electronic* and look for something electromechanical. That is, find something where you can take the case off, plug it in and see the innards moving. Then, if possible, you can start taking off components and driving them by hand to see what they did to contribute to the entire process. (This gear made the left beater spin, this made the right beater spin, this one connected the two of them together and made sure they didn’t hit each other, this shaft goes back to the motor, see what happens if I turn it…)
That way you can start by asking “What do you think happens what I push the on button” and see what they come up with.
Maybe a typewriter, eggbeater, adding machine, old dot matrix printer, a decent sized motor to show them the windings (might want to get the case cracked at home though).
FTR, this is what my kitchen table currently looks like.
*Electronic things were always really boring. I’d be all excited to have something to take part only to open it up and find a bunch of circuitry. What I wanted was moving parts, I wanted to see what made everything happen…you can’t do that with electronics.
ETA, I see several other people beat me to my suggestion to stay away from electronics.
I’m with Joey P, Crafter Man, Cheshire Human, and Francis Vaughan. Something familiar, with some mechanism, and preferably functional enough to at least operate partially. I vote for something like an older hard drive. They should be familiar enough to kids that have/had an iPod or PC at home, and even with the cover off the drive will spin up and the heads will move about. The drive will be ruined after this, but so what. Plus, there’s the benefit of it not having much in the way of hazards in there aside from some thin metal pieces. Also can draw a comparison of the control of the heads with a speaker, since the principle is the same.
If you can still get mechanical alarm clocks, that would be something nice - although I have not fond memories: twice I took the thingies apart, re-assembled all the parts and they still didn’t work. Grr. They were making me angry on purpose, I’m sure!
