Low-Budget Electronics Projects For High School? 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?
A-stable multivibrator (Score:5, Interesting)
555 Timer (Score:3, Interesting)
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.
A Theremin (Score:4, Interesting)
Have them make a theremin [wikipedia.org] (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.
Crystal Radio (Score:3, Interesting)
Crystal radio (Score:5, Interesting)
I'd start with a crystal radio [wikipedia.org], 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 [uoguelph.ca] and some LEDs.
All of these are low power, low cost, and produce a visible or audible result for immediate gratification.
Mal-2
Re:A simple oscillator (Score:3, Interesting)
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.
$5? Back in my day.... (Score:1, Interesting)
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? (Score:3, Interesting)
What about getting junked electronics (thinking Goodwill here, or possibly even donated) and desoldering components to build other projects with?
use an arduino clone (Score:2, Interesting)
Use an arduino clone.
http://www.arduino.cc/ [arduino.cc]
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.
electric guitar stompboxes? (Score:3, Interesting)
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.
Re:Do they still Sell 100-in-1 kits? (Score:3, Interesting)
Evolution doesn't control people's intelligence that much; the way they grow up does. And our society over the past 20-30 years has been in a serious decline.
Re:555 Timer (Score:3, Interesting)
Seconded. I have a very simple circuit for an IR repeater which uses a 556 (that's two 555s in one IC), three resistors, one capacitor, an IR LED and a TSOP 1736 IR receiver. Total cost is less than $5 with a small breadboard, the latter being the most expensive component. One of the 555s is (ab-)used as an inverter. If you don't care too much about protocol, you can do away with that and just have a 50% duty cycle on the output instead of the usual 25%. The IR repeater works with almost all IR remotes (those which don't work use different modulations and are really uncommon).
If you're looking for something more digital, building a counter from flip-flops is always instructive and provides the blinkenlights.
anything arduino (Score:4, Interesting)
its very simple. it gets you results FAST. very little learning curve.
I went from zero (or near zero) to a full running real-world program in a few days (talking to lcd displays, reading from an IR led and handheld AVR remote control, relays, leds, buzzers, etc).
the source code is all out there and its simple. you can find a lot of thru-hole chips that you can 'talk to'. chips are in the $5 range and need only a 50cent ceramic resonator (not even a crystal) and you're up and running.
at this point, anyone exiting school who CANNOT program microcontrollers (not computers, but the smaller controllers) will be left out in the cold. I think the next big thing is small controllers, not 'big' pc systems. get into this early, it will pay back and the ideas/knowledge gained map well to 'pro' level controllers.
Wind Generator (Score:1, Interesting)
a whole plethora of electronic and physics principles:
Weather; torque; electromagnetic force; volts; amps; ac; Phase the list is endless.
Its VERY relevant to all kids (green energy etc)... you can even roll it into "how to conserve energy" process etc..
and easy to teach how it works to make some very easy-to-build wood items out of scrap.
Strip a few hard disks and you get the magnets (be careful - they can be more dangerous... might want to use less powerful ones for kids);
strip an old TV for the copper wire stock. Stators made out of wood; props from wood...
or Look up VAWT (vertical)... and you can get some ideas of some basic designs (like a couple of coffee tins cut in half and put in 180o phase.
There are even whole teaching manuals on the 'net that will help you design the teaching program....
its all there for you..
Re:A-stable multivibrator (Score:5, Interesting)
The 555 can be used in a lot of interesting, simple projects. I like the idea of audio, because it's something that (IMO) a lot of young students will find interesting compared to some of the other typical beginning electronics projects.
One very easy 555 project is an Atari Punk Console [hackaday.com]. I built one of those a couple of years ago and took it to a party and it provided hours of entertainment.
Another option might be a simple resonant low-pass filter, since any of the students who've listened to electronic music will immediately recognize the effect and want to play with it.
Build a $5 Van de Graaff generator (Score:2, Interesting)
I did this one with my daughter for a science fair project. For me, the parts DID cost more than $5, but there were a lot of things I bought singly, but would have the cost lowered spread out over multiple applications; bag of rubber bands, one long piece of PVC, wood, nails, etc...Also many pieces can be brought from home to lower the cost.
While the results were never that spectacular, given more time, and less baling wire construction, it might be fun and educational. You can throw in lessons about resistors and capacitors then use it to power something bigger.While it won't help much for logic gates, you gotta start somewhere.
How to build a generator [scitoys.com]
Re:Good Luck (Score:5, Interesting)
I did something similar, except we were grab assing and I was vaulting my workbench.
My hand landed on the hot iron with my weight fully, though briefly on the hot iron.
Did you immediately jam the burned flesh into your mouth to cool it?
People still look at me oddly when I tell them that fried human flesh tastes a lot more like sauteed mushrooms than pork.
Re:Light bulbs and batteries (Score:2, Interesting)
No offence, but adding bulbs in parallel and series is a bit, well a bit basic. I'm not expert on the American education system, currently only being educated in the Scottish one, but my first year class (10-11), did that sort of thing - and that was science i.e. we hadn't decided on whether to take physics, biology or chemistry. And then when we were in 3rd year we learned the formulas that related to simple circuits and were expected to be able to describe electronics circuits (potential dividers, transistors, relays, light/heat dependent resistors etc.) and how different changes affected them and a basic description of how they worked.(e.g. light up, resistance down, more voltage across R2, high enough voltage for transistor to switch on, allowing current to relay, completing the motors circuit and switching the motor on) Then in 5th year, which I did when I was still 15(last year) - which I believe is about 9th grade - the higher physics course taught what semiconductors were, how they were used and the theory of how MOSFETS worked. So I don't know who moded you insightful, I'd say you were being down right condescending.
P.S. SciGuy asked about electronics, in first year we were taught that electronics were different to electrical circuits which you proposed teaching.
Also even though I was in first year only 5 years ago, the course has changed and they are expected to know even more by the end of 2nd year when they start Standard Grades.
Re:Good Luck (Score:3, Interesting)
I still want to give a swift cockpunch to my school for that same policy. I'm looking at paying to take a welding class at the local community college so I can work on my car.
Instead I had to sit around and take a Study Hall because god forbid smart people learn to do two things.
Re:Do they still Sell 100-in-1 kits? (Score:3, Interesting)
Jefferson wasn't writing for the common people, since literacy rates were so low, he was writing for other people like him. Wealthy members of the land owning class.
Universal education didn't exist till the late 19th century. My father, born in 1927, tells me that back when he was young it was common for older boys to be years behind their age level in class because they had been taken out of school to help on farms, though he says that sort of thing became less common as the years went by. In part due to mechanization and also in part due to US industry and government needing as many educated people as it could get.
People aren't dumber, it's just nowadays it's more than just the socio-economic elite who are getting educations, and getting pressured to go further than their ancestors were. In the old days no one cared if the kid of a sharecropper didn't have an education because for many people, those kinds of people didn't matter. They could just do the same job their parents did.
Nowadays, that sort of thing isn't tolerated.
Mimms, yes and Bill Beatty and BEAM (Score:5, Interesting)
I agree - the Mimms books are the place to look for basic, cheap yet informative and interesting projects. I used his "Getting started in Electronics" [amazon.com] to teach ages 9-12. To make this learning physics rather than just a craft project, it's crucial to teach the basics before doing projects with complicated circuits or chips. I mean at least voltage, current, serial resistance and parallel conductance using the water-flow analogies, and preferably the divided-pressure tank model of the capacitor as well (see Bill Beatty's "Capacitor Complaints" [amasci.com] Also read all his articles about "Electricity" [amasci.com] or you will be guaranteed to perpetuate misconceptions. Great teaching ideas there.) This is about as much as you are likely to have time for, but very little interesting happens in circuits without semiconductors, so if you can work in the fluid analogies for diodes (check valves) and transistors [satcure-focus.com] the kids will benefit.
My personal choice for an educational medium-basic circuit project would be a high-pass and a low-pass single-pole filter (both just a capacitor and a resistor). Use a computer sound card as a signal generator and spectrum analyzer using a free program such as OscilloMeter [corbina.net].
Other good projects would be an H-bridge motor controller [beam-wiki.org] (6 transistors) or for something more ambitious a Tilden "nervous net" / BEAM robotic circuit such as a light-tracking head [beam-wiki.org].
Re:Mimms, yes and Bill Beatty and BEAM (Score:3, Interesting)
I had the pleasure of seeing him teach his advanced second year class 2 times, once as a student and once I was in the room working an independent study, which allowed me to observe it all over again. He taught a couple of months each year about electricity. We learned a lot by making and playing with the electrophorus made of a piece of hard insulation foam, a pie plate, a styrafoam cup, and a piece of wool. We made our own leyden jars out of film canisters, foil and paper clips.
There was something that he seemed to know instinctively, which I realized the second time I watched him teach the course. The water flow analogies will make a lot of sense to a few of the students. The rest will build misconceptions based on the idea that electricity flows like water (it doesn't).
I always understood the analogy pretty well, but some were confused. For example, if students were taught one behavior of electricity and how much it was "like water" then they would start to predict that other behaviors of electricity would be "like water". At some point the analogy breaks down and people are saying "but but but, that doesn't make sense".
I had been playing with electronics since I bought my first iron at 9 or 10 years old. This left me watching other kids in the class trying to learn the stuff I thought came naturally. I could understand water analogies, but most kids in the class would nod confusedly. It finally clicked with me that the ONLY reason I understood the water analogy was that my father was a landscape irrigation contractor, and a farmer. I had been around water flowing in pipes since I could walk. I used to build crap out of the fittings and scrap pipe.
What you have to realize is that the average high school student knows nothing about plumbing. They know that they turn the knob and water comes out. For previous generations this may have been different. If you grew up a farm kid "changing the water" in the fields like I did, then you might get it. If you were very mechanical and had worked on a radiator, you might get it. But most kids these days grow up playing with electronics instead. You would be much better off explaining water flows in terms of an electricity analogy than the other way around.
Keep in mind, that in most of the systems where you think of water flowing, it only flows because of gravity. Electricity flows for a fundamentally different reason. I believe the better way to teach electricity is by teaching a simple understanding of the Bohr model of the atom. If you can ask your students to bear with you for a few minutes, and explain that the Bohr model is a good but not perfect model of the atom, just as Newtonian mechanics is a good but not perfect model. Explain to them quickly, and non boringly electrons, protons, neutrons, and the forces involved. Explain valence electrons, conductors and insulators. Then start talking about a simple electrical circuit. Explain it in terms of a flow of electrons (do NOT teach hole flow!) from negative to positive.
The water analogy does have its place, I just think teachers need to be careful if they think "I will explain it in SIMPLE terms... like water in a pipe". The behavior of water in a pipe i
Using the criteria ... (Score:4, Interesting)
2) Teaches about circuits that are relevant to their life.
3) Doesn't rely too heavily on a black box microcontroller.
4) Individual components would probably be better.
5) I want them to understand the circuitry behind modern tech.
Given these criteria, I would vote, go for a flip-flop. Even the name appeals to kids. Its also historically the basis of a lot of digital electronics design. Its also fun as kids can see the LEDs working and replacing the resistors with potentiometers makes it easily to alter its speed interactively which is always fun for kids to see.
For example...
http://talkingelectronics.com/FreeProjects/5-Projects/Page16.html [talkingelectronics.com]
But I would say, as you are teaching electronics, before you move onto the flip-flop then first show them a single Transistor with a small switch wired to its base, showing the Transistor can itself act like a switch (use it to control an LED). They need to learn how transistors switch. (You can go onto explain about amplifying later
Both the flip-flop and the switch with a transistor + LED (and a few resistors), all adds up to less than $5 for the lot and you have a few important lessons easily covered in an interesting and visual way.
You can also make the flip-flop switch faster so they can't see the LEDs flashing any more, and then connect up a small cheap speaker, so they can hear it buzzing to show its still flipping. Its a very interactive way for kids to learn electronics, and its cheap and easy to make without even needing a circuit board. Just use tinned wires to form the circuit exactly like its circuit diagram.
Hand wound motor (Score:2, Interesting)
It would require two magnets, some magnetic wire, a battery, two paper clips which are the 'brushes', some copper tape for the commutator, some sort wooden/metal rod to mount the rotor onto, and bigger piece of cylindrical wood for your commutator. This might blow your budget the first year, but i would see the only recurring expense be the copper tape, batteries and the magnetic wire.
Here is a website on how some of the assembly should look
http://hades.mech.northwestern.edu/wiki/index.php/Brushed_DC_Motor_Theory [northwestern.edu]
Look about halfway down the page when describing the theory.
My only pointers would be to make a multi-turn coil of wire instead of a single single. Obviously you will need to add a rotor and commutator, so that is what the various wooden pieces are. Make the copper tape cover as much of the circumference of the commutator, as it will work better.
I found another, simpler DC motor, but it didn't look to exciting. You can search google to find other types of projects.
Re:Using the criteria ... (Score:3, Interesting)
Why call it a flip-flop when you can give it it's proper name: an astable multivibrator?
A classroom full of sniggers is guaranteed.
Sound or Motors.... (Score:2, Interesting)
I know you said you were looking for something more electronics, but for Physics there is no reason not to just stick with stuff that is the most fun and engaging: real hardware, and things that do something physical or make a sound. A lot of electronics projects are just tedious whereas movement or sounds give great feedback!
Everyone loves taking old CDROMs apart. Connect a LED to the motor and pull the drive in and out - very satisfying, cheap, simple and easily leads to discussion of physics. This video has some fun things to try with a small motor: http://www.youtube.com/v/WnWJki-zwsE [youtube.com]. The most consistent positive response I have had is playing with the tray on old CDROMs using a battery to make it go in and out - kids and adults get a real kick out of it! They love the gear mechanisms too!
Personally I feel more can be learnt by pulling something familiar apart - many people have never had the opportunity to pull apart something and understand the workings. Even better if you can use the parts in some simple manner (for some reason using a *real* part from something else is more exciting!). Making something from new components is often simplified to the point where it is too detached from obvious real world usage, and loses the interest of students.
I would hope you can find a suitable source for recycled bits; we have a local computer recycler with cheap stuff - boxes of old speakers from PCs, or boxes of old CDROMs, etc. But small motors and speakers can be bought cheaply.
I also love self-made bolt+wire electromagnets (a favorite classic), speakers + sound sources, switches, relays, and potentiometers.
Anything to do with sound just engages. I have just had play with a speaker and 12V - fun sound with metal surfaces! Sparks are awesome if you can supply them - votage and a speaker (or motor inductance) is enough ;) The pencil line and speaker idea in another post was interesting, but probably needs to be amplified (I just measured an HB pencil line as 10's of kOhms for a multiply overdrawn dark line) - beautiful example of resistance though.