Become a fan of Slashdot on Facebook

typodupeerror
DEAL: For \$25 - Add A Second Phone Number To Your Smartphone for life! Use promo code SLASHDOT25. Also, Slashdot's Facebook page has a chat bot now. Message it for stories and more. Check out the new SourceForge HTML5 Internet speed test! ×

## 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?
This discussion has been archived. No new comments can be posted.

## Low-Budget Electronics Projects For High School?

• #### A-stable multivibrator (Score:5, Interesting)

on Wednesday July 15, 2009 @05:55PM (#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
• #### Light bulbs and batteries (Score:3, Insightful)

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 t

• #### Re:Light bulbs and batteries (Score:5, Insightful)

on Wednesday July 15, 2009 @06:43PM (#28709593) Journal

I disagree that capacitors and transistors are too advanced, or at least NEED to be taught in an advanced way. The goal is not necessarily to teach them how to design complex circuits, but to get them familiar with the ways the components interact.

Anecdote: I was building projects using transistors and SCRs as early as 6th grade. This included layout and chemical etching of my own circuit boards.

Let's see how many of the projects I can remember doing...

- Soil moisture sensor. Using a cut piece of double sided circuit board as a probe, connected to a small battery operated circuit that measured the resistance between the two sides. When the resistance rose above an adjustable threshold (via potentiometer) an LED would turn on to let you know the plat needed watering.

- "Concentration" game - an SCR and buzzer were used to make a game where you passed a metal loop over a bend metal wire without them touching. Once the two parts touched, completing a circuit, the SCR would latch on and the buzzer would sound until the reset button was pressed. I recall this project also used a voltage regulator.

- "Hide & Seek" game (aka the most annoying thing on the planet. Great for young students!). A set of transistors (4 as I recall) connected with a series of resistors and capacitors would periodically sound a short beep out of a small PC speaker. Duration, tone and period of the sound were adjustable by selecting the component values. As a bonus we were encouraged to find items at home to hide the circuit in - I used a hollowed out video cassette (switch under the flap) and hid in in my dad's video collection, complete with fake label :)

- 4-digit electronic keypad switch. A series of buttons were wired to transfer charge between a series of capacitors, and ultimately to an SCR that would latch a relay to control whatever you wanted to hook up to it. Combination was set by wiring the buttons differently.

- Roulette wheel. A series of LEDs (in a circular pattern) was connected to a small collection of ICs that would cycle them around and stop on one. I honestly don't recall what the ICs were, though :(

- Parallel port PC interface: Control up to eight 120V-10Amp relays via the PC's parallel port. (Included writing "driver" software)

- EQ meter. Build a resistor/diode network that, when fed an (amplified) audio source, caused a row of LEDs to light up according to the music volume.

- Various other blinkenlight projects :)
=Smidge=

• #### Re: (Score:2)

No! "Continue Editing" not "Submit!" Arg...

Please forgive the typos in the above post.
=Smidge=

• #### Re:Light bulbs and batteries (Score:5, Informative)

on Thursday July 16, 2009 @01:16AM (#28712789) Journal

Deciding I needed a PWM for a project, I wanted to build my own to learn about electronics...so I went to radio shack and bought their \$79.99 Electronics Learning Lab.(this kit alone is HOURS of amusement and learning)...but what I learned quickly is that following the Mimms book was very wasteful...the explanations of what is happening is scant...the diagrams are great, but blinking leds and making buzzer noises just ISN'T practical to a freshman in High School(I've taught them Freshman computing and mentored them in many aspects of I.T.)...

Below are some sites I've come across searching for 'simple enough for a basic solderer' and with readily available components(strip parts out of busted old computer power supplies/vcrs/radios/etc)..

http://www.electronics-lab.com/projects/audio/023/index.html [electronics-lab.com]

something fun and useful...a 'hearing aid' =) ... the entire site is useful

http://www.aaroncake.net/circuits/ [aaroncake.net]

some things more complex...

http://sci-toys.com/index.html [sci-toys.com]

fun and educational .. some real easy stuff...and some more challenging stuff...

Hope this post ranks high enough for you to find it.

• #### Light bulbs are old, make a Joule thief... (Score:5, Informative)

on Wednesday July 15, 2009 @09:16PM (#28711125) Homepage

Make all those 'dead' batteries run little torches:

http://www.emanator.demon.co.uk/bigclive/joule.htm [demon.co.uk]

• #### Re:A-stable multivibrator (Score:4, Funny)

on Wednesday July 15, 2009 @06:40PM (#28709557)

Astable multivibrator

don't you have to be over 21 to buy those?

• #### Re:A-stable multivibrator (Score:5, Informative)

on Wednesday July 15, 2009 @07:45PM (#28710289) Homepage
There is a great little circuit for something called a "Drawdio" http://web.media.mit.edu/~silver/drawdio/ [mit.edu] that kids really love, basically it's an astable 555 that makes a noises with pitch proportional to how long they draw pencil marks. (it's a bit hard to explain quickly, just try the video on that website)
I teach middle school aged kids electronics at a local workshop, building things such as that, and I can tell you it's very doable to make projects for cheap that kids can build and understand.
The main issues that I have found is the board on which you lay out projects. Breadboards are expensive, and not permanent. PCBs don't allow kids to experiment with their own circuit designs, and unless you are going to take the time and money to let them design their own boards that might not work and then etch them, it's more trouble than it is worth. We use a more traditional breadboard concept that is just an actual, wooden board. Then we have kids use copper tacks and strips to lay down the circuitry, and then they solder things directly to that.
As other people have mentioned, soldering irons are a bit annoying, and a couple kids might get some mild burns, but as long as you don't mind the initial cost, it's totally doable.
One of the great things about the drawdio project, is it allows you to hook it up to a oscilloscope and show the kids more about sound, or hook the piezo speaker up to a computer and run some FFT software, so they can see and hear how the resistance changes the pitch.

Other things to look into are basic transistor circuits, things with opamps, counters, or things with binary to decimal or binary to seven segment LCD chips.
• #### Re:A-stable multivibrator (Score:5, Interesting)

on Wednesday July 15, 2009 @08:26PM (#28710727) Homepage Journal

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.

• #### Do they still Sell 100-in-1 kits? (Score:5, Informative)

on Wednesday July 15, 2009 @05:57PM (#28708953) Journal

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: (Score:3, Informative)

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.

• #### Nand Gate or Power Supply (Score:2)

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 (Score:3, Interesting)

on Wednesday July 15, 2009 @05:58PM (#28708967) Journal

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: (Score:2)

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

• #### Re: (Score:3, Informative)

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

• #### Re: (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 (tho

• #### A Theremin (Score:4, Interesting)

on Wednesday July 15, 2009 @05:58PM (#28708973) Homepage Journal

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.

• #### Re: (Score:3, Funny)

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

• #### E-Meter (Score:3, Funny)

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.

Better yet have them build an E-Meter [wikipedia.org]. Since it is just a Wheatstone bridge they can learn something about physics. It doesn't produce spooky music but it would be great for scaring their parents at Hallowe'en.... "Mum, Dad look what I got for signing up with the scientologists!".

• #### Re:A Theremin (Score:4, Informative)

on Thursday July 16, 2009 @01:19AM (#28712807)

The problem with the Theremin is that to make a working example based on the principle of the original (capacitive coupling between the hands and antennas changing the frequency of an LC oscillator) is actually a fairly complex project - you have to understand about how LC oscillators work, the superheterodyne principle (the pitch oscillator is the difference frequency between a fixed and variable RF oscillator), transistor amplifier principles, etc. Of course, they can be built from kits, but just building from a kit doesn't really provide any insight into the functioning of the circuit.

A project that maintains the spirit of the original but might be easier for 9th graders to get a handle on might be the optical theremin [instructables.com]. It only uses a few parts, and the basic operation of the 555 timer and light dependent resistance should be approachable for newcomers to electronics.

• #### Nice book (Score:4, Informative)

on Wednesday July 15, 2009 @05:58PM (#28708975)
• #### A simple oscillator (Score:4, Informative)

on Wednesday July 15, 2009 @05:58PM (#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: (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.

• #### Oscillator? (Score:3, Insightful)

on Wednesday July 15, 2009 @05:59PM (#28708981) Journal
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 (Score:3, Interesting)

on Wednesday July 15, 2009 @05:59PM (#28708991) Homepage
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: (Score:2)

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.
• #### circuit simulation. (Score:2)

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.

http://www.electronickits.com/kit/complete/kita/ck800.htm [electronickits.com]

• #### Two suggestions (Score:2)

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

• #### Crystal radio (Score:5, Interesting)

on Wednesday July 15, 2009 @06:03PM (#28709063) Homepage Journal

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

• #### Optical Theremin (Score:5, Informative)

<cbacigalupo@gmail.com> on Wednesday July 15, 2009 @06:04PM (#28709079) Homepage
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 /.
• #### Have them build things (Score:2)

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.

• #### Cost effective? (Score:5, Insightful)

on Wednesday July 15, 2009 @06:07PM (#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.

• #### A few off the top of my head (Score:2)

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

• #### Virtual Reality (Score:2, Informative)

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 [quinndunki.com] out there.
• #### Desoldering old stuff? (Score:3, Interesting)

on Wednesday July 15, 2009 @06:13PM (#28709211) Homepage Journal

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

• #### Simple LED Lights! (Score:2)

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 y

• #### Literally thousands of projects (Score:2)

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 co

• #### scitoys.com (Score:2)

Check out scitoys.com [scitoys.com] 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.

steveha

• #### 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)

on Wednesday July 15, 2009 @06:21PM (#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.

• #### BEAM robots (Score:2)

Make little moving junkbots, examples: Mark Tilden's [beam-online.com].
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 [wikipedia.org]
• #### A few ideas (Score:2)

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 [amazon.com] is probably stocked with good ideas.

Using a wire wrapping tool [radioshack.com] could be a good way to construct circuits without using solder. You can also use breadboards [radioshack.com]. 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

• #### DSE (Score:2)

Knock yourself out
http://search.dse.com.au/nav/cat2/electronicsandkitsets_kitsets/cat1/electronicsandkitsets/0 [dse.com.au]

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...

• #### LED lighting circuits (Score:2)

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 (Score:3, Informative)

on Wednesday July 15, 2009 @06:26PM (#28709361) Homepage
I think the scrounging idea is a good one...you'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 (Score:2)

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.
Done

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

• #### Lewin Edwards (Score:5, Informative)

on Wednesday July 15, 2009 @06:29PM (#28709407) Homepage
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) - http://www.larwe.com/technical/2260lcd.html [larwe.com] 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 http://www.geocities.com/SouthBeach/6897/photovore.html [geocities.com] If you want to liaise further, feel free to contact me using that website.

on Wednesday July 15, 2009 @06:33PM (#28709459)
Get the chemistry teacher to help you and make a trench(foxhole) radio. Then build a crystal radio. Then an audio amplifier circuit. Or build the crysal radio then the audio amplifier then the foxhole radio. But actually building a radio with parts they've made and not bought, making the diode, will teach them a lot.
• #### 555 timer (Score:2, Funny)

At school in 10th grade we had to build a diorama based around a 555 timer. I was playing half-life at the time so I wanted to incorporate the alarm sound from the 'resonance cascade' at the beginning. I asked my teacher if I could do that and he went mental. Apparently he had just given a 15 minute lecture about why we wouldn't be able to do that and I wasn't listening... :-\
• #### Tagged 'domyjobforme'? Really? (Score:5, Insightful)

on Wednesday July 15, 2009 @06:37PM (#28709519)

Why is this tagged 'domyjobforme'? There's a negative connotation there.

This is an (awesome sounding) teacher looking for suggestions on how to expose kids to something worthwhile.

You aren't doing his job for him until you're working for his salary, on his budget, and care enough about your students to step outside the curriculum once in a while for education's sake.

What is this, the Hipster Olympics? Do we win by looking down our noses at people?

• #### anything arduino (Score:4, Interesting)

on Wednesday July 15, 2009 @06:38PM (#28709523)

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.

• #### Light + sound + electricity = awesomeness (Score:2, Informative)

Unfortunately, I don't remember the circuit exactly, but one of the most interesting demonstrations I saw was transmitting sound from an iPod using an LED shining on a solar panel, amplified with what I believe was a single transistor and a 9-volt battery, and finally played through a speaker.

Cheap solar panels are fairly easy to come by, courtesy of Edmund Scientific and the like. The other parts can all be scavenged from various cheap sources and broken things. Incidentally, I'm also in favor of high-scho

• #### small electronic organ (Score:2)

Your budget limits you to a couple of ICs a stripboard and a few other components. Use something like a 555 with an LM386 audio amp and various C / R combinations for the tones. However, before you start them on electronics, you'll have to buy some soldering irons and teach them to solder - provided your health and safety regulations allow such hazardous activities.
• #### 555 ICs are God. (Score:5, Informative)

on Wednesday July 15, 2009 @06:39PM (#28709549) Homepage
There are so many things you can do with an 555 IC that it's not even funny. Digikey has them for 44 cents per unit here. [digikey.com] With a handful of descrete components you can create everything from flip flops (with 2 555 ICs) to oscillators to time delay circuits. (some example circuits. [cogeco.ca])
I suspect with a handful of 555 ICs, descrete circuits, ICs and switches (or just touch wires together), you can easily create a whole host of illustrative experiments that show the idea behind modern gate circuits. And I'm sure you can easily do it all for a few dollars worth of components, though unfortunately breadboards can be quite expensive. (Around \$8 for a small breadboard through Digikey, though you may be able to find cheaper.)
• #### Telegraph (Score:2)

You could build a rudementary electric telegraph system within your budget. Press down the button, it causes a "click" by magnetizing a clap-bar. Very simple circuit.

• #### Don't bother (Score:2)

Kids in America not only have no interest in things like science and electronics, but there's not going to be any jobs in it when they finish college. So teaching this stuff to them is a waste of time. Stick to teaching them things like marketing and law, since that's what they'll all want to go into in college anyway.

• #### Metal Detector (Score:2)

Get creative with parts. Use cardboard or sheet plastic for the circuit board material (careful not to melt the plastic with soldering irons). Use a cereal box, or some other small box, or PVC for the project box. Get the kids to bring creative parts from home.

Build a metal detector. [easytreasure.co.uk]

The Electronic Goldmine [goldmine-elec.com] and others offer assorted parts in an unsorted box for cheap. You could buy bulk parts like this and have the kids sort them (make them learn how to measure componen

• #### Magnet, AM radio, plus others (Score:2)

I think there is a kit out there for just \$23,148,855,308,184,500

Why not have them build their own crystal AM radio, totally old-school style? Wind their own coils, use a piece of wood for the base and another for the coil form (piece of hardwood dowel?). You can still find 1N34 or 1N60 germanium diodes to use as the detector, and just about any ceramic disc 0.01uF capacitor for the filter. Most expensive parts would be the 365pF variable capacitor and a crystal headphone; magnet wire of an appropriate gauge would be relatively cheap per unit, coming off a single spool.
• #### Night-light with timer (Score:2)

You could make an LED night light with a timer shut-off. This would be about as simple as you can get with active components. Probably best to use a potentiometer to adjust the time delay - in real use, you'd want >30 minutes, but the kids will want to try it out with 30 seconds.

• #### Multimeter (Score:3, Insightful)

on Wednesday July 15, 2009 @07:15PM (#28709957) Journal
Have them build a multimeter. They'll wind up with a useful gadget, one they can use on future projects.
• #### Two quick projects: Data readers. (Score:2)

There are two projects I think are well suited for this purpose. A CC stripe reader or a SIM card reader. Both are very simple circuits, both require exactly one specialized piece of hardware (the SIM reader or the tape reader--and old cassette player head works fine). Both can provide data to the COM port to any computer, and need only very simple software to manipulate.

• #### Have to keep it simple, try RELAYS (Score:3, Insightful)

on Wednesday July 15, 2009 @08:34PM (#28710787)

Hello-
I have some experience with this problem. You're right that microcontrollers are too advanced, everyone gets bogged down in the development tools. I also find that most types of IC and transistor circuits where you can't SEE what is happening don't really work out for most kids.

A few kids will get really into it. The next group will 'sort of' get things to work by following the directions, but not understanding what is actually happening. The rest will just sit there while everybody else plays around. They won't even try.

I have found that the basics like lightbulbs, batteries, and switches really get kids excited. They can see what's going on and they understand it and start building on it. Flipping a switch or pressing a button to make something happen is very empowering.

Next, if you can get a hold of some nice relays, especially ones with clear housings, they are really useful for this. It's a switch that turns on another switch. They understand it. (especially with a DPDT knife switch to explain things) Try a reed switch and a magnet, controlling a bulb through a relay. (small switch controls big switch... They learn about current) Let them try the NC contacts. Show them a relay LATCH. Connect the coil through the NC contacts for a relay buzzer. Add a speaker across the coil for a louder buzz. Can you combine these and make a burgler alarm? Show them that a mechanical bell or buzzer is the same as the NC relay buzzer. Next, put a capacitor on the relay coil for a delay. They will UNDERSTAND all this and get into it. And they like the clicking.

This lets them learn by using things they understand like switches and bulbs which are all doing things they can actually see. There are no black boxes at all. Also, a lot of kids want to ignore you and just play. With these parts, they can still make things happen and learn just by messing around. Can they get the relay to click? Make the bulb light up?

I've taught a lot of workshops to beginners and most breadboard type stuff really just confuses them. It seems they have made up their minds in advance that this is something they can't do, it's too hard. With the knife switches, batteries, bulbs and relays, they got really excited. When we added the capacitor they really understood what those did. It seems that this is a necessary first step before you move on to 'black box' parts.

Once you've gotten them there, the next thing is an optoisolator, which is really just a relay. Then they're comfortable with a DIP package, and you can proceed to the 555 and such with the ones you haven't lost. In the meantime, skip all semiconductors completely, except the rectifier diode, which they understand, and maybe the LED (with resistor already soldered on).

As we get better at electronics it becomes more and more difficult to understand what it was like to not know anything about electronics. You try to explain a 555 or op amp and there are a thousand details that you're taking for granted without knowing it. The other person really can't get it without the details, which makes it very hard to teach the subject without losing people. This is why you should go for the basics as much as you can. Let them play in that safe zone and master it and build a foundation before moving on.

Skip Ohm's law and the RC circuits and the math stuff for now. Let 'em turn things on and off. They'll get it.

List: Knife switch, lever switch with roller, button. Reed switch and magnet. Buzzer, bulb, rectifier diode. Clear relays, at least SPDT, DPDT better. Capacitor that can hold the relay on for 1 sec. LED with resistor installed. Speaker with resistor inline (so it can go across the battery without blowing up) . Batteries to match all these (9V or 12V is easiest)

Show them some examples and let 'em go nuts!

• #### Power Supply/Small BJT Amplifier (Score:3, Insightful)

on Wednesday July 15, 2009 @10:14PM (#28711579)
How about a power supply they can use to charge their small devices? All you need for a basic power supply are a transformer, some diodes, resistors and capacitors. Or a small voltage divider bias BJT amplifier? a couple capacitors, an NPN transistor, and some resistors. Could be used to amplify music coming from an iPod and show the principals of amplification.
• #### Options at \$5 each (Score:3, Informative)

on Wednesday July 15, 2009 @11:45PM (#28712233) Homepage

At \$5 each, there are few options. Rainbow Kits [rainbowkits.com] are a possibility. The "blinking lights" and "1W audio amplifier" kits are both under \$5.99. That's about as low as you can go.

• #### Analog vs Digital circuits for teaching Physics (Score:3, Insightful)

on Thursday July 16, 2009 @05:45AM (#28714247)
If you want to teach PHYSICS, I recommend against digital circuits. There is much more Physics to learn from Analog(ue) circuit design and implementation. Indeed the first circuit I ever built was an AM radio reciever, according to instructions found on my school Physics textbook: "Physics for Today and Tomorrow" by Tom Duncan (IMHO the best Physics book ever) The component count is very low, about 10 components... the most expensive and difficult to find? of which are the the ferrite core and the variable capacitor. An AM radio receiver can be used to teach about electromagnetism, resonance, electronics, etc. Students wishing to go that extra mile can attempt to also build an AM transmitter (this can be even easier to build.)
• #### Simple transistor audio amp for MP3 players (Score:3, Insightful)

on Thursday July 16, 2009 @10:54AM (#28716905) Homepage

I would suggest a project that is simple enough to understand, yet has a demonstrable practical circuit that they may choose to use after the class is over. One idea that quickly comes to mind is a simple (2-3-transistor or 2-3-per-channel (stereo)) audio amplifier, suitable to powering a small speaker, with a jack to connect to MP3 player.

It demonstrates one of two basic modes of operation for transistors, one of the most important semiconductor devices (diodes and ICs are others) that is a building block for analog (and digital) electronics. The other mode is when the transistor acts as a switch BTW.

You can cover electron and conventional current flow, waves (sound), and feedback as physics topics.

For the parts, using a mail-order suppler like Digi-Key [digikey.com], Mouser [mouser.com], or Jameco [jameco.com] (US / Canada) you should be able to buy the parts for about \$5 including the connector and a small speaker.

See Simple 3 Transistor Audio Amp (50 milliwatt) [bowdenshob...cuits.info] from Bill Bowden's hobby circuits [bowdenshob...cuits.info] web site.

#### Related LinksTop of the: day, week, month.

Nothing makes a person more productive than the last minute.

Working...