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Low-Budget Electronics Projects For High School?

timothy posted more than 5 years ago | from the does-school-policy-rule-out-ieds? dept.

Education 364

SciGuy writes "I am a physics teacher for 9th graders. I really want to teach them modern electronics (something beyond the light bulb and battery). My hope is for a project that: 1) Is fun 2) Teaches about circuits that are relevant to their life. 3) Doesn't rely too heavily on a black box microcontroller. Individual components would probably be better. (I realize that #2 and #3 are probably contradictory. They will already be programming in my class but I want them to understand the circuitry behind modern tech.) 4) It must be as cheap as possible. Yay, public school. Unless some of the parts can be scrounged or found at home, I would probably want to keep the project around $5." What would you build?

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$5? (-1, Troll)

Anonymous Coward | more than 5 years ago | (#28708887)

Just take them to Subway and buy them lunch. They'll be better off.

Jewish scum (-1, Troll)

Anonymous Coward | more than 5 years ago | (#28708959)

With Jews you lose so in order to win you must lose the jews, whitey.

Re:$5? (1)

linuxisashittyos (1574017) | more than 5 years ago | (#28709171)

5 dollar foot looooooooooooooooooooooooooooooooooooooooooooooooooooong!

use spice (0)

Anonymous Coward | more than 5 years ago | (#28708901)

Re:use spice (5, Informative)

ocularDeathRay (760450) | more than 5 years ago | (#28709343)

another option, and I just mentioned him on another story the other day... is take a look at the old forest M Mims III books. They are the books that they used to sell for a couple bucks at radioshack. You can still get them from his website, or a few other places (saw them at Fry's the other day) although they cost a few dollars more now. I started reading his books in the 4th grade and I have worked and played with electronics ever since. Each of his books have schematics (and a guide on how to read them) for many projects which can be built for a few dollars on a breadboard. I would suggest looking at something with a simple linear analog IC like a 555 or 556 timer.

If you go to you can get component grab bags, or my favorite are the component kits. For example the resistor kit has a selection of common values and a nice plastic storage thing that keeps them nice and neat. Give every student a few LEDs from a grab bag, a 555 timer chip, a battery, some jumper wire, a handful of capacitors and resistors from a couple of component kits, and the schematics to make a simple LED flasher. Then the different students will have different values of resistors and capacitors, and will get different results. Then you can time the flashing of each students project and chart the values of resistor, capacitor, and time. Explaining simple RC circuitry is a good place to start teaching somebody electronics.

The Mims books also get into digital, you could buy some simple nand gate chips and show the students all the different ways to use them, use simple push buttons for input and LEDs for output to save money. It may not be super exciting, but you could build an inventory over a couple years to do something really cool. Use TTL chips, not CMOS because the students will ruin CMOS with ESD. The possibilities are really endless. Any students who really get excited can buy a handful of parts online and build all sorts of neat stuff from those books. There are circuits for opto communications devices, a shortwave radio, a break beam sensor, you name it, its in there.

A-stable multivibrator (5, Interesting)

yoshac (603689) | more than 5 years ago | (#28708913)

Astable multivibrator is a simple circuit, useful (flash lights at high RC values, make sounds at higher values), and teaches the basics of transistor, capacitor and resistor in a practical manner

Re:A-stable multivibrator (0)

Anonymous Coward | more than 5 years ago | (#28708961)

And the lesbians in class will love him.

Light bulbs and batteries (3, Insightful)

PleaseFearMe (1549865) | more than 5 years ago | (#28709247)

Both items are familiar to the students, so they can be tricked into learning something new. Have them connect light bulbs in series, then in parallel, to see how the brightness changes. Add batteries in series. Add batteries in parallel. Once they are familiar, have them connect ammeters and voltmeters for numerical interpretation. This would give them a solid intuitive feel for how circuits work.

I would not teach them anything about transistors and capacitors until later, because that would require too many advanced concepts. Make sure the students do not feel overwhelmed by the material. If the students feel confident about what they are doing, ie. it makes sense that adding in more batteries makes it brighter, then they will be inquisitive to learn more, and confident enough to set out on their own.

Good Luck (1)

aitikin (909209) | more than 5 years ago | (#28708949)

The only thing I can think of is to have an additional fee for this project, unless you're looking at something like the light bulb that you were referencing. The other key thing is, do you have enough irons to go around. Not everyone solders or even knows how to at all, so you need to make sure that you have enough soldering irons for the students either to work individually or as small groups.

Re:Good Luck (3, Informative)

Sparr0 (451780) | more than 5 years ago | (#28708983)

I don't think soldering irons are a requirement for this idea. Breadboards, or even springboards, would be much more appropriate, I think. Cost per student goes up, but overhead goes down.

Re:Good Luck (1)

aitikin (909209) | more than 5 years ago | (#28709127)

Meh. I learned starting on PCBs, granted crummy quality PCBs, but PCBs nonetheless.

Re:Good Luck (1)

91degrees (207121) | more than 5 years ago | (#28708985)

Is soldering really a good idea at this level? I'd have thought a modular breadboard would be better for learning. It makes correcting mistakes a lot easier.

Re:Good Luck (1, Insightful)

Grishnakh (216268) | more than 5 years ago | (#28709045)

Soldering has no place in a public school. 1) Someone will burn themself, and sue. 2) Someone will sue because of exposure to hazardous materials, or some government agency will get involved.

Besides, soldering assumes you have PC boards to solder to. Solderless breadboards are easier and safer, as long as you stick with thru-hole components.

Re:Good Luck (1)

ocularDeathRay (760450) | more than 5 years ago | (#28709145)

I burned myself, in public school, in high school physics, while soldering. Pencil iron was sitting funny in the stand, so I grabbed it, as you would grab a pencil but just in front of the grip. 5 minutes later I was in my chemistry class and it was a scantron final... get out your number two pencils... hurts to think about. seriously though, if they can have shop classes with welding I am sure they can have soldering.

Re:Good Luck (1)

Chabo (880571) | more than 5 years ago | (#28709253)

I had a high school chemistry class just a few years ago where we cut open pennies, melted the zinc inside them, and flung the molten zinc out onto the counter. Only one kid burned his hand.

Compared to that experiment, soldering is safe. I would say "as safe as bowling", but bowling causes a fair number of injuries annually.

Re:Good Luck (3, Informative)

tattood (855883) | more than 5 years ago | (#28709297)

You didnt have a shop class in high school? I took metal shop and got to play with welding torches. That had a much higher potential for getting seriously hurt than a soldering iron.

Do they still Sell 100-in-1 kits? (5, Informative)

JSBiff (87824) | more than 5 years ago | (#28708953)

When I was middle-school age, I had a *great time* with these kits sold by Radio Shack. They were basically a bunch of cheap electronic components fixed on some sort of board, with connections, and a bunch of wires you could use to connect the components together into different circuits. It even came with a book with like 40 or 100 (I don't remember the number, really) different circuits 'plans' for simple types of things you could do with the kit and discussions about how the circuits worked.

They cost like $10 or $20 back then (probably be $30 or $40 now, not sure though).

I would *highly* recommend looking into something like this. They are maybe a bit more expensive than you discussed, but they are re-usable and allow you to create lots of different things. Heck, you could maybe even figure out how to use multiples of the kits and maybe a few additional components to create something a bit more impressive to demonstrate to the class how larger electronics systems are created by configuring each kit into a specific type of circuit, then joining the kits together (that is, each kit becomes one 'components' of a larger system, maybe).

Re:Do they still Sell 100-in-1 kits? (2, Informative)

Brigadier (12956) | more than 5 years ago | (#28709037)

They still have these but I can't imagine them having the longevity to stand up to ninth graders. After using mine for a few months most of teh spring had become elongated and knobs lost.

Re:Do they still Sell 100-in-1 kits? (-1, Troll)

Grishnakh (216268) | more than 5 years ago | (#28709081)

I disagree. Back when you were a kid, kids were not only smarter than kids now, but more inquisitive and interested in things like this.

This whole project is just a big waste of time, assuming it's in America. Instead, stick with teaching kids about boring things like law and marketing or advertising, since that's what they're going to be doing when they grow up anyway (either that or working in fast-food).

Re:Do they still Sell 100-in-1 kits? (4, Insightful)

JSBiff (87824) | more than 5 years ago | (#28709219)

B.S. Evolution doesn't happen on timescales of 20 years (I'm only 31). Kids aren't any smarter, dumber, or less or more inquisitive, except to the extent that no one has lit their imaginations on fire yet. But, it sounds like this teacher at least wants to *try*. More power to him, and I hope he finds something which fits his classroom needs.

Truly smart, creative engineers and scientists don't need to find jobs - they *create* jobs (often, not only jobs for themselves but good paying jobs for many other people). So, I'm not too worried about America's future, as long as we actually *try* to educate and excite kids about science and engineering.

Re:Do they still Sell 100-in-1 kits? (1)

Nyall (646782) | more than 5 years ago | (#28709379)

Methinks the previous poster was referring to society not evolution.

Re:Do they still Sell 100-in-1 kits? (1)

Chabo (880571) | more than 5 years ago | (#28709263)

Are you just bitter? I know plenty of young kids who are really interested in science, even more than I was at their age.

This may be the age of emo, but keep in mind that Generation X was the age of "Whatever."

obxkcd (1)

oGMo (379) | more than 5 years ago | (#28709439)

#603 []

The only person who is less smart now is you.

Re:Do they still Sell 100-in-1 kits? (1)

Zsub (1365549) | more than 5 years ago | (#28709203)

I agree. I used things like these [] at my school. They have several ports, like an AND-port, also there is a AD-converter, several inputs (high-low or variable voltage), a counter, and some more. It really is all you need to teach simple circuitery and can be used in (small) groups.

I just found out those weigh in at â 389,00, which is quite pricey... :(

Nand Gate or Power Supply (1)

Dysan2k (126022) | more than 5 years ago | (#28708965)

A nand gate would be good to build with transistors since those are used in RAM and modern circuits. Also power supplies can't go wrong either (for charging a cell phone or something.)

555 Timer (2, Interesting)

avandesande (143899) | more than 5 years ago | (#28708967)

I would do something with a 555 timer, there are a ton of applications and although you may consider it a 'microcontroller' all of the support electronics (pots, leds, resistors) will be instructive. Throw in an SCR to drive a high watt light bulb.

Re:555 Timer (1)

Grishnakh (216268) | more than 5 years ago | (#28709133)

Exposing kids to AC and high-watt light bulbs will certainly result in someone getting shocked with 110VAC. Not a good idea.

Re:555 Timer (2, Informative)

avandesande (143899) | more than 5 years ago | (#28709259)

Getting shocked as a teenager builds character. I should know!

Re:555 Timer (0)

Anonymous Coward | more than 5 years ago | (#28709345)

It might build character, or it might turn you into Grishnakh.

A Theremin (4, Interesting)

davidwr (791652) | more than 5 years ago | (#28708973)

Have them make a theremin [] (see the "Similar instruments" section as well). It makes spooky music. Great for a late-October/Halloween project.

You can even make this inter-disciplinary with the music teacher, the English teacher, the history teacher, and the Russian teacher as appropriate.

May be a bit expensive (1)

davidwr (791652) | more than 5 years ago | (#28709017)

At over $40 a pop for a basic model from a kit, this may have to be a group project.

Re:A Theremin (2, Funny)

fm6 (162816) | more than 5 years ago | (#28709187)

Now that's a good suggestion. The only risk is that all the students will become fans of really weird movies [] !

A simple oscillator (3, Informative)

Zaphod-AVA (471116) | more than 5 years ago | (#28708979)

I'd recommend a simple oscillator project. You can use it to either flash two LEDs or create tones for a speaker. It covers the use of transistors, resistors, and capacitors. The cost should be very low, and the project can be put together without solder in several different ways. Here is one article with an example. []

Re:A simple oscillator (2, Interesting)

harrkev (623093) | more than 5 years ago | (#28709149)

Another trick is to make it in the audio range, and then have the kids draw a black square on a piece of paper with a pencil. The graphite (carbon) will appear as a variable resistance based on where you put the wires (put one wire at one end and move the other wire around). This will make a kind of crude music synthesizer. All for the cost of a 555, a speaker (piezo is fine), a battery, a battery holder, and a handful of resistors and capacitors.

Oscillator? (2, Insightful)

fuzzyfuzzyfungus (1223518) | more than 5 years ago | (#28708981)

Virtually anything digital will have one or more oscillators in it. The kiddies might well have fun with a 555 or discrete based oscillator. All the components(with LED or nasty little speaker to output the result, and a potentiometer or resistor selection for playing with frequency) are dirt cheap in even modest quantities and the theory of operation is a step above bulb 'n battery without being super tricky.

Crystal Radio (3, Interesting)

typosquatting (1586073) | more than 5 years ago | (#28708991)

Crystal radio - tons of fun, relevant to kids (music), super cheap. There are kits online, but a little more expensive than your budget ($12 - $15). I'll bet you could get the cost down by buying the raw parts in bulk instead of individual kits.

Re:Crystal Radio (1)

Pajaro (95016) | more than 5 years ago | (#28709109)

I don't remember where (Make magazine?), there was this project to make a VERY LOW cost radio with just wire and a wire hanger (and maybe some earphones?)

Finding it via google is left as an exercise to the reader...

You might also get lots of ideas in Make Magazine, the do lots of do-it-yourself projects, and most are cheap.

Re:Crystal Radio (1)

16384 (21672) | more than 5 years ago | (#28709327)

The hardest part of building a crystal radio is finding a suitable headset. But you can build a simple "radio" with just a 741 or two. A simple amplifier with a wire as an antenna will pick up some transmissions, no need for a tuner.

Consider some simple transistor circuits (1)

richardkelleher (1184251) | more than 5 years ago | (#28708997)

Consider simple transistor circuits. There is a book out there called The Encyclopedia of Electronic Circuits that has hundreds of simple circuits.

Look at circuit design software like AutoTrax (Kovac Software). He has some great education pricing. They can design circuits, run SPICE analysis and then build them and verify the results.

model railroading... (1)

macbeth66 (204889) | more than 5 years ago | (#28709007)

Model Railroading offers many opportunities to build things that have an immediate purpose. Blinking LED projects, sound, electronically controlled motors for crossings.

I built a small N scale project that needed three voltages; 3, 12 and variable 12 volts. I used one of those old laptop bricks and a few voltage regulators, diodes, caps and resistors and I was all set. BTW, I knew nothing about electronics, just kept reading as much as I could and it started to make sense. It really helped to mix something I knew ( modeling ) with something new ( electronics ) with a simple goal, make some trains run.

As for cheap, most of the parts were free through scavenging and some were bought from Digi Key.

circuit simulation. (1)

Brigadier (12956) | more than 5 years ago | (#28709009)

I woudl imagine with cost being the driving factor you are very limited. As most modern circuits would require a resonable power supply, ocilloscope, plus components. This being said since you sound like you already have computers look into getting a simulation program that will allow you to build circuits virtually and test them. just a though.

(random google search) []

Photovore Robot (0)

Anonymous Coward | more than 5 years ago | (#28709023)

A couple of photo-resistors and transistors to drive simple gear motors ( Wire everything to a proto-board for easy rewiring and reconfiguration. Hook the photo cells to drive the motors on the same side of the bot (R-R, L-L) for light avoiding behavior, and cross the wires (R-L, L-R) for light seeking. Bumpers could also be added which kills power to the motors with only switches and no other components.

This would probably run more like $20 but would get a base ready if they wanted to pursue microcontroller based robotics in the future. Also things that move have a tendency to grab kids attention.

Astable (0)

Anonymous Coward | more than 5 years ago | (#28709027)

A-stable multi-vibrator.

Attach an of LED and bam, cheap way to teach rudimentary capacitor/transistor theory.

You should teach them how to use 555 timers (0)

Anonymous Coward | more than 5 years ago | (#28709033)

the 555 timer is a great IC and there's lots of cool things you can do with it.

That and a few proto boards would make a fun project

If it was 2nd grade ... (0)

Anonymous Coward | more than 5 years ago | (#28709035)

... I would suggest them building a bristle bot!

Two suggestions (1)

dlakelan (43245) | more than 5 years ago | (#28709047)

Hardware random number generator using a couple of resistors, a potentiometer, and a zener diode. For additional points, use a comparator to amplify the noise. You can then talk about the physics of electron transfer across the diode junction and thermal agitation to describe why the noise occurs.

Another interesting project is a feedback controller that levitates a ball hanging below an electro-magnet. You use an LED and a phototransistor to set up a circuit that tries to keep the reflected light intensity constant, which makes the steel ball hang a certain small distance below the magnet.

Neither of these is too terribly expensive, and both have physics content, but neither is what I'd call "modern". Almost all of modern electronics involves digital integrated circuits.

cell phone charger (0)

Anonymous Coward | more than 5 years ago | (#28709051)

They like cell phones (you may have noticed). You can charge current cell phones from usb. Swipe a USB cable from a pawn shop and get some 7805 regulators from digikey/newark/jameco. Add a 6 volt lantern battery, and you can charge your cell phone anywhere. Or grab some cigarette lighter plugs from the pawn shop and you have a car charger. Total cost should just barely come in under your $5 level, *and actually be useful and relevant to them*.

Rectifier/transformer (1)

telomerewhythere (1493937) | more than 5 years ago | (#28709061)

I know it would be more than $5, but a project that would power their cell phone... (5 volt usb from 120 volt source)

It's related to something they're interested in already. Some will like, others will electrocute themselves.

And then we will find you under the bridge, transformed to a oscillating hunchback.

Crystal radio (5, Interesting)

Mal-2 (675116) | more than 5 years ago | (#28709063)

I'd start with a crystal radio [] , although there are designs far more compact than the one on Wikipedia. Next, perhaps a simple transistor amplifier (for which you can use the crystal radio as an audio source), then it might be time to move on to the thousand and one projects you can build around a 555 timer chip [] and some LEDs.

All of these are low power, low cost, and produce a visible or audible result for immediate gratification.


Optical Theremin (5, Informative)

micromegas (536234) | more than 5 years ago | (#28709079)

I just taught a unit on electronics. We used breadboards and the 555 ic to build optical theremins. I have the entire curriculum done. contact me through /.

Laser communicator. (0)

Anonymous Coward | more than 5 years ago | (#28709083)

Every kid has headphones....and those laser pointers can be had for like 2$ on ebay

PIC's are fun (0)

Anonymous Coward | more than 5 years ago | (#28709089)

Once you get past the sunk cost of a programmer, a PIC is a great way to go. You can get free samples on any of them. Beyond that:

Solderless Breadboard
Battery Source

Should be had for around $5

Opportunity (0)

Anonymous Coward | more than 5 years ago | (#28709091)


I agree that this type of opportunity should be seen more even in college. I would take a look at the SparkFun website. You can also contact them, I know they hold events in various places to up electronics interest. They may have a program to purchase simple projects in bulk at a discount rate for schools. I have purchased many items from them for various electronic projects I have worked on.

Have them build things (1)

geekoid (135745) | more than 5 years ago | (#28709107)

the next class can use to build more things.

VOlt meters, O-Scopes cards for a computer.

You could also go to the local place that people donate there crap computers, get a coupkld of those and build a cprogramable PCI card. Possible get one donated for a local electronics corporation.
For example, if you are in Oregon, contact Intel and see if you can get donations from them. They, and Mentor Graphics, were very helpful to our school when they did the robotics tournaments.

Try the Heath Corporation (0)

Anonymous Coward | more than 5 years ago | (#28709113)

If they are still in business or you can find somebody who still has their old texts.

Heath had a dozen continuing education courses in core electronics with over a hundred interesting projects from 555 timers to Digital Techniques and Logic.

All you need is a breadboard with low voltage power, the discrete components (most of witch have a price in the pennies. A multimeter, and in some cases access to an oscilloscope.

The courses were not expensive, may be still available, and I bet somebody in the community still has them tucked away in their attic.


Solar Engine cars? (1)

Subverted (1436551) | more than 5 years ago | (#28709125)

I would recommend something like a solar engine car or something similar. These are both cheap and easy for kids to make. Plus, you can have the kids race them. ;) Something like this, perhaps they could work out a deal with you to get it down to a more reasonable price: []

Cost effective? (4, Insightful)

girlintraining (1395911) | more than 5 years ago | (#28709131)

$5 won't buy you much if you buy the components individually. You need to buy them in lots -- in which case you can afford a lot more room to experiment. Also, some equipment can be re-used, like breadboards, multi-meters, etc. When considering the project's costs, don't neglect economy of scale. It might be cheaper for everyone to simply have a "lab fee" and buy enough to last a few years.

Batteryless Flashlights (0)

Anonymous Coward | more than 5 years ago | (#28709161)

I would work with the kids on batteryless flashlights. Build off the concepts of a dynamo and capacitance system and you end up with not only a good project for low cost, but a useful household item with a "green" solution.

A few off the top of my head (1)

smellsofbikes (890263) | more than 5 years ago | (#28709169)

Wheatstone Bridge-based "lie" detector. Two resistors, a pot, some wire (you can use paperclips with bends in them to hold people's fingers and reduce slightly the ease with which this can be gamed.) Either measure directly across the bridge with a voltmeter or amplify with a transistor and drive an LED. You could use the more traditional galvanometer but that breaks your $5 budget. But everyone loves something that allows them to ask you rude questions to try and make you sweat.

There's always the good old motor made of a coil of magnet wire, a battery, and a magnet.

For a little more than $5, you can buy a bag of cheap laser diodes off ebay, a couple of 1k-to-8ohm audio transformers, and a photodiode or photovoltaic cell (keep it as small as possible) and build something that plugs into an mp3 player phono jack and transmits sound via laser. Here's one implementation [] , and many others exist. I've built these and they're pretty easy.

For that matter, since laser diodes are so cheap, you can also make a pretty good seismometer with a laser diode, some cheap crappy fiber optic cable in a tangle, and a photodiode. The fiber optic could even be glass you've drawn, if I recall correctly.

I've made several coilguns, but those are a little more exciting. Wind up a good coil of magnet wire, around a core of lots of welding rod cut at different lengths. Put a hoop of metal, preferably aluminum, around it on top of the coil, and briefly connect the coil to 110v, and watch your metal hoop fly. With some care in coil inductance and adding some caps for tuning, you can put a ring through a piece of plywood.

I'd go for the AM radio (1)

cats-paw (34890) | more than 5 years ago | (#28709175)

diode, resistor and capacitor. It will drive a _very_ high impedance earphone.

antenna is a _long_ piece of wire, or get the ferrite version from a junker radio.

it's modern electronics and is wireless ?

add a little pizazz with an op-amp as an audio amplifier.

Audio splitter? (1)

citylivin (1250770) | more than 5 years ago | (#28709177)

An audio splitter for, a mp3 player, or just a headphone jack split. Maybe you could put in some circutry to amplify? Or get some kind of custom ipod cable (ive heard that they are popular mp3 players). Maybe some buttons and stuff to switch tracks?

I am sure if someone made electronics relevant to me in that way when i was growing up, i would have busted out the soldering iron alot sooner than I did.

Virtual Reality (2, Informative)

macragge (413964) | more than 5 years ago | (#28709201)

I know how fun it can be to get your hands dirty, and its amazing how empowering it feels once you realize that you can build your own circuts, but if you're on a tight budget, why not turn to simulated circuts. There are plenty of flash apps and games like Gate [] out there.

$5? Back in my day.... (1, Interesting)

Anonymous Coward | more than 5 years ago | (#28709207)

Assuming you have the proto boards already, $5 is not out of line for a number of fun little projects.

If they are programming already though, you're closing a whole world of fun by not letting them interface to them e.g. a thermistor temperature sensor is pretty boring, a temp sensor that records the last 24 hours to ram and lets you dump it to your computer is a "tool of discovery."

I think an ATtiny2313, with it's 2k of ram, 128 bytes of SRAM, 128 bytes of flash and hardware UART makes a great interface to whatever electronics they are working on, and is not so much a "computer" that this becomes a software project. So with $2 per project tied up with that chip....

Start with the "transistor based" port-powered RS-232 interface instead of the max232. They'll learn about using transistors as switches, and it's easy to t-shoot when it's done wrong.

Now any analog circuit you want to show them is the cost of the components and hooking it to the 2313's analog comparator, one leg of that comparitor can be tied to a voltage divider, letting them set the cut-offs in "analog world."

A couple seven segment LED displays or an 8 segment bargraph can make for instant feedback.

It makes it easy to:

        * Check the optimal angle of a solar cell over 24 hour period.

        * Wire up 8 output leads power-of-two resistors to make an analog output that they can use to tweak analog circuits like audio warblers.

        * Use the PWM output, a capacitor and inductor to drive a motor and illustrate (I trust you own a scope) power smoothing and switched power supply operation.

        * Use an old floppy head-positioner leadscrew to adjust a solar panel's angle based on it's output

        * For advanced kids:
              1. Creates 10khz RC oscillator, use transistors (or cheat and use an LM386) to amplify it to a small speaker, gate it with an output from your microcontroller....

              2. Put an simple pair of high-pass and low-pass filters on your mic. input (centering on 10khz), rectify it, and have it trigger a debounced input to the micro, and with a little help from the onboard timer, you have cheap sonar, which is very very fun.

          I think the analog world is best discovered with the help of digital recording and determinism, but it's your $5...

Desoldering old stuff? (2, Interesting)

nizo (81281) | more than 5 years ago | (#28709211)

What about getting junked electronics (thinking Goodwill here, or possibly even donated) and desoldering components to build other projects with?

Re:Desoldering old stuff? (0)

Anonymous Coward | more than 5 years ago | (#28709377)

If you desolder with solder wick, you may spend more money on solder wick than the components are worth (e.g. 5 cents for a resistor or a red LED). Other means for desoldering which are cheaply available are also aggravatingly ineffective.

Re:Desoldering old stuff? (0)

Anonymous Coward | more than 5 years ago | (#28709453)

Or how about just tearing stuff apart? We did that with my middle school science class. There was a bunch of donated/garage sale type electronics, we pulled the shells off and started poking around inside.

Send out a flyer to the kids asking for broken/dying/ancient electronics they haven't tossed that they want to pull apart in school.

Not really reusable though and this is high school so parent's aren't as involved as say, elementary school.

Breadboards might be the best bet.

7segment display is everywhere! (0)

Anonymous Coward | more than 5 years ago | (#28709215)

7 switches to turn on different segments.
Then you can introduce the decoder and binary (BCD) numbers translated to decimal display.

Simple circuits (1)

djl4570 (801529) | more than 5 years ago | (#28709225)

A simple transistor oscillator is a good place to start. A simple class A voltage amplifier can be built with one PNP or NPN transistor, a few resistors and capacitors. It's a good way to demonstrate how small changes in the base current regulate the current flow across the junction. Old fashion TTL chips are still available. Five dollars worth of TTL chips, some LEDs for output indicators, some breadboard sockets can help students understand how logic gates such as AND, OR, NAND, NOR work. Ambitious students might cobble together a four bit ALU. It would give them an appreciation of the computer in their cellphone. Frequency splitter circuits such as those used in speaker crossover networks might be of interest. These can show how capacitors block low frequency. All of these can run on low voltage

Keep it simple and relevant to course material (1, Insightful)

Anonymous Coward | more than 5 years ago | (#28709227)

You're going to have a tough time building anything practical for a $5 budget. I'm going to assume you mean $5 per student with a class of around 30 - you can't usually buy resistors or the like in quantities of "1", and just a (decent) breadboard can't be had for less than $5 unless you're buying in bulk. It would be best to have each student (or small teams) build it themselves. If you're at the front building and describing, they'll just tune out.

I would build some simple resistor ladders, which is probably all the course material covers. Have them put several LEDs in different parts of the circuit, and then play with the number and size of resistors in each leg of the ladder to show them, visually, that the voltage and current are changing.

You can show them capacitors by putting the battery in parallel with a big-ish cap, then have them remove the battery and watch the LED slowly dim and die.

If you want to bring transistors into the mix for sub-$5, it'd probably have to be a single transistor switching the power supply, with a pull-up wire to turn it on and off. You could maybe move it to different legs of the ladder. But I'd actually advise against transistors unless you want to go all-out and have them build an AND / OR gate. If you just show them transistor == switch, without showing them all the useful stuff it can do, they won't be very impressed.

If you have a digital multimeter, it would also be very instructive to build one demo circuit at the front of the class and measure the voltage at different points, to show them the values and prove something really is happening in there.

Anything more complicated than this, like RC oscillators or inductance, is going to be both expensive and way way over the heads of a 9th-grade class. At least, if you actually want to teach the physics of what's happening. If you just want to say "connect thingy A to jigamabob B and watch the light blink!" then sure, go for it!

Simple LED Lights! (1)

millisa (151093) | more than 5 years ago | (#28709233)

LED lights are a cheap fun way to teach some basics. All you need is a battery (or even better, several different batteries with different voltages), an LED (or several LED's with different voltages), and a bunch of resistors.

You can get packs of green, red, and yellow LED's for less than 50 cents an LED. resistors are a buck for packs of 10. And batteries are batteries. Figuring out the resistor needed to light up an LED based on the voltage from a single battery or series of batteries can be neat.

If you want to take it a step further, bring in some 50 cent USB a-b cables. Slash them and toss out the B side, find the 5V and ground line, and have them figure out the resistor needed to light an LED for USB voltage (like a woot light!). USB power = 5V 100ma usually (it goes up to 500ma, but the driver usually has to negotiate it up; it should be 100ma; buy a cheap powered hub if you want to keep it safe from the computer). There are lots of links on how to figure out the voltage of an LED, this one is ok. []

Keep it simple (0)

Anonymous Coward | more than 5 years ago | (#28709249)

You need to keep it simple, but fun.

I used a photo sensor, small transistor, power transistor, and 1Amp 12Volt light bulb.
Wired to when sensor sees light, bulb goes out.

If it sees itself, it makes an oscillator.

If multiple folks in the class make them, they interact.

You maybe able arrange them into gates and flipflops if you have enough.
    (Also an opportunity to try fibers.)

    (I also tried a smaller bulb for the bias resistor so you can see what is going on in the circuit, but that was too much for the kids.)

The circuits were built on a 2 by 6 inch pcb with the copper cut in half length wise.
    One side was ground, the other side +12.
    Parts soldered in 3d above the copper.

Power from a gel cell with a series ballast to prevent fires.
    Ballast was 4 tail light bulbs in parallel.
    This lights up nicely when you short something out.

Literally thousands of projects (1)

digitalhermit (113459) | more than 5 years ago | (#28709251)

With a couple junk telephones you can build a radio. There are even some guides here and there that show you how to make a variable potentiometer, switches, batteries, etc., from tin and aluminum cans and a few sheets of acetate (such as in a clear plastic report cover).

Old remote controls, busted transistor radios, old calculators are a goldmine. With them you can make some very simple circuits. For example, with a few transistors and diodes you can make a binary adding machine. It can demonstrate how a computer does a shift or an add, AND, ORs, etc..

There's a page online somewhere with instructions on how to build a car that drives around. When it approaches a wall it will turn around. It uses pieces scrounged from motherboards and CDROM drives. (1)

steveha (103154) | more than 5 years ago | (#28709271)

Check out [] for some ideas. The section with a radio is pretty darn cool, and he does have a few simple projects like a 1-Watt amplifier and a laser audio transmitter. No soldering needed, which is a plus for a school setting with 9th graders.


use an arduino clone (2, Interesting)

unix_geek_512 (810627) | more than 5 years ago | (#28709283)

Use an arduino clone. []

Check out the Rock Bottom Freeduino Kit @ http://wulfden/ [wulfden] ( dot ) org/TheShoppe/freeduino/rbfk.shtml

Link has been edited to prevent the site from getting slashdotted.

Razor-blade Radio (0)

Anonymous Coward | more than 5 years ago | (#28709291)

I built one of these when I was a kid. Talk about low-cost. And you can skip the tuner part. The combination of pencil lead and a razor-blade acts like the diode. So, if you have a strong enough signal, you can get by without the fancy tuner.

electric guitar stompboxes? (2, Interesting)

dunkelfalke (91624) | more than 5 years ago | (#28709293)

a small guitar amp or an overdrive stompbox are pretty easy to build from discrete components and you can hear if they work or not.

Analog electronics components are cheap and fun (1)

DUdsen (545226) | more than 5 years ago | (#28709295)

You can make all sorts of feedback curcuits with a few transistors(act as termostats) some swicthes, a few resitors a few LM324 ot similar amplifies and maybe some more advanced sensors, this kind of stuff is a few doller a set at a bulk retailer, you can make oscilating lights controled by stuff happening in the room with some diodes again dirt cheap and som RC(resistor capacitor) circuits.

"AND" gates are also avaliable cheaply so you could do all sorts of digital fun aswell.

BEAM robots (1)

euxneks (516538) | more than 5 years ago | (#28709303)

Make little moving junkbots, examples: Mark Tilden's [] .
Most equipment can be scrounged from old parts that a University would gladly donate to get rid of (for instance, Capacitors, resistors, etc.etc.) There are also parts in old electronics just thrown out at the dump, and the kids get to learn how to read information on the electrical components.
Oblig. Wikipedia Article []

Strobe light (0)

Anonymous Coward | more than 5 years ago | (#28709305)

A friend of mine made a stobe light in his high school science class. His plugged into the wall, but a safer and lower-cost option would be to use a battery. It had a pot on it, so he could vary the frequency of the strobe. He also made a cool case with a reflector. You could do this with a few RLC components, a couple of transistors, and an LED bulb. A quick google search will provide you with a variety of schematics that will meet your cost and complexity constraints.

A few ideas (1)

CopaceticOpus (965603) | more than 5 years ago | (#28709315)

I played a lot with these sorts of projects when I was young. I really enjoyed the little books by Forrest M. Mims III at Radio Shack. This book [] is probably stocked with good ideas.

Using a wire wrapping tool [] could be a good way to construct circuits without using solder. You can also use breadboards [] . The breadboards are easier to work with, and can be reused by several classes. However, with the wire wrapping approach, you may be able to make the project cheap enough for the students to keep what they build.

I once made a "darkness detector" or night light which would light up an LED when a room was dark. It was kind of cool because it all fit inside a little plastic film canister. All it needs is an LED, a photoresistor, a watch battery, an on/off switch, and a transistor. (And perhaps a simple resistor.) It can all be wired up using the wire wrapping tool. It's more of a toy than a useful item, but it's so cheap that it could be something they can take home to keep.

Tesla Coil (1)

downix (84795) | more than 5 years ago | (#28709319)

A common Tesla Coil can be made for this budget simply, and would definately get any childs attention. basic schematics can be found all over the net.

DSE (1)

labnet (457441) | more than 5 years ago | (#28709325)

Knock yourself out []

As an aside, 25 years ago I won a competition in high school with dick smith with a prize of $50 worth of electronic components.
I was thinking beauty, the things I'll be able to make!
What did I get?
just what every kid wants... a box of 5000 22pF NPO capacitors...

old computer stuff (0)

Anonymous Coward | more than 5 years ago | (#28709341)

A computer power supply will give you 5 volts and 12 volts. They are completely enclosed and safe.

A CRT monitor will give you a bunch of parts. In particular, the horizontal oscillator transistor is virtually bullet proof. The de-gaussing coil is a good source of magnet wire. You have to find a way to get rid of the CRT tubes safely. Don't leave any of the circuitry together, especially the power supply. A monitor power supply isn't protected and has totally dangerous voltages.

Old floppy drives are good for stepper motors. The controller board takes only a couple of signals, step and direction. You can drive the controller board signals with the parallel port.

I used to epoxy stepper motors and microswitches to lego blocks for student robotic projects. Another favorite project was a class A audio amp using the aforementioned horz. output transistor.

You can teach electronics for just about nothing. For an oscilloscope, you can use a computer sound card.

LED lighting circuits (1)

mauriceh (3721) | more than 5 years ago | (#28709351)

Calculations involving current, voltage, resistance, and parallel circuits.
LED lighting strikes me as useful, fun, and certainly a range of skills to build.
Cheap too.

Scrounge, Circuit Bend, talk to local Radio Shack (2, Informative)

CommieLib (468883) | more than 5 years ago | (#28709361)

I think the scrounging idea is a good'll be able to pull resistors off of anything, and everybody will learn the codes quickly. Have them bring in something simple in their house that doesn't work - have them troubleshoot and repair it (permission, obviously...).

Have them bring in an annoying electronic toy and have them wire a volume control into it. For that matter, have them bend circuits on all the electronic crap that surrounds us today.

Finally, talk to your later Radio Shack / Fry's / whatever, and see if you can get them to sponsor the class with some free gear and projects.

If you end up with some more coin, try a TV-B-Gone: []

AdaFruit has a lot of good stuff. One thing I saw at a Make Faire was a project where you quickly build an oscillator using a paper circuit board and a pencil line drawn on a paper to have a quickie musical instrument.

Static Electricity (1)

Sponge Bath (413667) | more than 5 years ago | (#28709373)

Bring out the carpet and sneakers, then *pop*.
Combine the exercise with theory.

1) Is fun
For the aggressor

2) Teaches about circuits that are relevant to their life.
Everyday relevance

3) Doesn't rely too heavily on a black box microcontroller.

4)It must be as cheap as possible
It does not get any cheaper.

Kronecker_Delta (0)

Anonymous Coward | more than 5 years ago | (#28709381)

I don't think I could suggest anything as low as $5, but have you looked into Arduino boards? They are fun, cheap and easy and would be perfect for high schoolers. I am using them in my own high school level education program teaching rocketry and using arduino to design the science payloads they carry. If you could get a little startup money you could buy the boards and easily spend $5/year per student on the jumpers and devices to do the experiments and learn the physics.

a crossover for a speaker (0)

Anonymous Coward | more than 5 years ago | (#28709391)

cheap because it uses passive components and demonstrates the attenuation concept. Filters can be applied to all kinds of signals. Selective tuning, notch filters, lot's of fun can be had with a fewelements!

Build a bunch of small circuits. (0)

Anonymous Coward | more than 5 years ago | (#28709393)

Have everyone build a nand gate. Combine these nand gates into or and xor gates. Build a half adder. Chain the adders together to form a full bit. Wire up a 555 timer to push in a bit and show that the adder is adding each new bit to the value. If you want to keep accumulating these small circuits over time you could build a full working computer that is 4 bit and has a few bytes of data storage.

Try Tanner Electronics (0)

Anonymous Coward | more than 5 years ago | (#28709403)

Tanner Electronics in Dallas has a bunch of low cost kits for beginners. Give them a call and see if they have anything you might be looking for.

ask fatMan and CirutiGril (1)

shareme (897587) | more than 5 years ago | (#28709405)

ask FatMan and Circuit Girl.. CircuitGirl is the one that di dthe old style game sin one little game controller to run on one [] She also does chip fabrication without caustic chemicals using household chemicals and easy bake ovens..

Lewin Edwards (5, Informative)

larwe (858929) | more than 5 years ago | (#28709407)

I am working on some similar projects for 11-12th graders though my budget is more in the $10 per student range. There are challenges with doing this without (a) soldering - and the risks, and (b) lead exposure. Anything intended for kids younger than 13 needs to be Pb-free to meet CPSC guidelines and avoid liability issues. For 9th graders you might need to check ASTM regs also regarding choking, entanglement, etc. It's a bit of a bear and it becomes harder the younger the kids get. I am using largely recycled components from junk cellphones and other sources (TDMA cellphones in particular are available dirt cheap and have lots of interesting projects) - [] documents some of my reverse-engineering though it doesn't explain why I'm doing it). A couple of interesting projects that can be made without soldering (just twisting wires) - Use a Hall effect sensor or reed switch, in combination with a light (LED, bulb, whatever) and a handful of small magnets to demonstrate making a "recording". Glue the magnets onto a strip of paper, or just use a piece of tape sticky-side up. Pull the tape past the sensor and watch the bits as they're read out on the bulb. Works best if you color say all the north poles red, so they can work out what is 0 and what is 1. - Make a light-following robot with two pager motors. There are a load of designs around, this one is not the simplest but is illustrative [] If you want to liaise further, feel free to contact me using that website.

DC Permanent Magnet Motor (0)

Anonymous Coward | more than 5 years ago | (#28709417)

Made one of these in a college power systems class. All you'd need is a magnet, some wire, and a D battery. Teach your kids about electricity and magnetism at the same time.

Want to add more electronics? Spin the motor and measure the voltage across the terminals, use the micro controller to convert the voltage to rpm display.

I have hundreds of ideas (0, Offtopic)

Hognoxious (631665) | more than 5 years ago | (#28709423)

Since (along with 99% of the world's population) I can't covert "9th graders" to meaningful SI units, I'll keep my suggestions to myself and you can whistle Dixie for all I fucking care.

War Criminal Tracker: (0)

Anonymous Coward | more than 5 years ago | (#28709431)

To find Richard B. Cheney et al. []

Thanks for your efforts in crime fighting.

Yours ELECTRONically,
Kilgore Trout

Page of suggestions and Old School option (0)

Anonymous Coward | more than 5 years ago | (#28709433)

This MeFi entry has a bunch of suggestions:
Where are the beginner-level electronic kits to be found? []

Not the safest option, but could always go old school and have them build their own capacitors, inductors, batteries and make basic circuits... Just need pvc tube, copper sheet, copper wire, lead sheet, etc.

parallax (1)

inerlogic (695302) | more than 5 years ago | (#28709445)

parallax has all kinds of kits on electronics and microcontrollers.... and they do volume discounts for educators....

blah blah black box microcontroller.....
what are they learning programming with?

check out the "what is a microcontroller?" kit...
it's based on a BASIC Stamp, and yes, bloack box, etc etc.... but... the kit has a proto board and many "basic components"

it;s better than going to adio shack and buying a bunch of parts they won't be able to use for anything else...

boo circuits! hooray electronic phenomena!!!11one (0)

Anonymous Coward | more than 5 years ago | (#28709447)

You're a *physics* teacher ... show them "lifter", "swimming LEDs", "neon life" or that experiment that MIT professor does where he generated high voltages with nothing but buckets of water a buckets ..!

Radio shack project books (0)

Anonymous Coward | more than 5 years ago | (#28709457)

Radio shack used to sell learning books/pamphlets in their electronics section.

The large one was by forrest Mims, but might not be sold anymore.

along with that they sold small 8X5 softback books, with around 40 pages that taught basic electronics theory.
they were called "Engineer's Mini-Notebook: "
the topics included
The complete set includes:

        * 555 Timer Circuits
        * Basic Semiconductor Circuits
        * Communications Projects
        * Digital Logic Circuits
        * Environmental Projects
        * Formulas, Tables, and Basic Circuits
        * Magnet and Sensor Projects
        * Op-amp IC Circuits
        * Optoelectronic Circuits
        * Schematic Symbols, Device Packages, Design and Testing
        * Science Projects
        * Sensor Projects
        * Solar Cell Projects

Search on for "Forrest Mims" (note the spelling of the first name)

Most of the mini-notebooks are less than $5 and are available as used. He has updated his books and they sell those on amazon as well.

You should be able to find a simple project for your students to build for less than $5 or $10 bucks.

good luck

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