Idea for a simple electronics project

Just about any functional block that uses more than 4 or 5 Rs, Cs, and/or Ls and no active components is either so sensitive to component values that you won't get it to work, or attenuates the signal so much that it can't do anything interesting.

So, you might consider circuits that switch between several different functional blocks.

For instance, you could make a selectable audio filter, that let you switch between RC or RLC passive highpass, lowpass, bandpass, and notch filters; you could then feed some music through it and listen to the output, and hear the effect.

I guess if you include LEDs and diodes, then you can also do a few very simple logic operations. For instance, you could make an LED turn on if any "M" (or more) out of "N" possible inputs are shorted to ground. I don't know how interesting that is, though.

Surely this is an entry-level class, so surely there are some advanced students who have already completed this class. How about asking some of them what projects they worked on?

You have many resources open to you, including fellow students who may be at a higher skill level and your college library.

I will add that I question the value of the assignment if your instructor is specifying that many components for an (apparently) beginner-level course. Also, as others have pointed out, that many R, L, and/or C components with no actives is not going to be able to do anything truly useful unless you're doing advanced passive filter design.

Another resource that you may be overlooking is whatever population of amateur ('ham') radio operators is in your part of the world. If you can find a club in your area, it could prove to be a viable technical resource. Granted, I have no clue what the hamateur environment in Israel is like, but it could be worth a shot.

Happy hunting.

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My recommendation is that of between all the projects that you find, choose the easiest of all. Do not try to choose something very complicated, simply choose one that you can really make without great problems.

Well, these requirements seem to be shouting "Crystal Radio". It's just an LC filter with a detector diode and a pair of headphones. The crystal (diode) is an active component but it's only just one, and an easy-to-understand one.

Your biggest problem would be getting the component count up to 20. A triple-tuned rf stage does nicely, as shown in this write-up.

Dear Dr. Anton and others who tried to help me,

Thank you for your efforts to help me. Unfortunately me and other students in my college still have the problem with that task, except those students who already work in electronics area. This requirement of our instructor is stupid, since I see it is impossible to construct any project, based on R,L,C elements only. You're right.

Best Regards

A small Tesla coil maybe? No active components and a rather dramatic output. It'll take serveral series/parallel caps to get the parts count up.

Seeing as that the requirement to have at least 20 components is quite silly, make a silly circuit in return! Make 10 RC filter circuits, each with a different resistor value. Connect the inputs together, fed in a signal and then measure the output with an AC voltmeter or CRO and plot a graph of the results and compare with the theory. Give it a fancy name like "filter response compliance verification test" or something!

Dave :)

Without an AC or DC power source, or some means to detect or use the output, what is the point of any circuit ?

However, assuming you can add more than passive components, a great place to start is

- and I suspect you can buy this magazine even in Italy. Possibly your library has copies.

See also

H

Perhaps part of the project (whatever it turns out to be) could be an AC-to-DC converter, just to help get the component-count up. You could get more details by googling or looking in electronics books, but it would include:

1 transformer, to convert line voltage to non-lethal levels (eg. 9 volts). 4 diodes + 1 capacitor, for a full-wave rectifier 1 voltage regulator + 2 filter capacitors, for steadier DC voltage.

That's 9 components, now you need to come up with a DC circuit using 11 components, about 1/2 of the original requirement.

Mark

just an

Well now, I wouldn't go that far. ;-) The diode is a semiconductor, but AIUI it is still a passive component since it cannot create gain in this application. :-) I would say that it can't create gain in any application, but someone would probably demonstrate that it can. ;-D

I do think the crystal set is a good idea though. It's easy to make work then the OP can spend the rest of his/her time adding active circuitry to improve its performance.

how about a graphic equaliser?

4 or 5 bands should get your parts count up there.

Bye. Jasen

Fair enough.

I hear various definitions of active and passive components that seem to allow the detector diode to edge into either category. I think of an active component as one that is powered. Detector diodes are often biased to improve sensitivity, as was the one in the link I provided. That's why I classified it as an active device, even though it has no gain.

Other types of diodes, impatts and tunnel diodes for example, can amplify signals. But of course we're not talking about those sorts of diode for a crystal radio.

Well, it IS impossible to construct an electronic circuit from only those. The difference between ELECTRONICS and ELECTRICITY is **ACTIVE DEVICES**.

I like Walter's idea (Jasen's is quasi-similar). An old receiver with a Preamp Output and an Audio Input

will make his idea duck soup[1] to demonstrate. Just make a network that is complicated enough to get up to the required parts count. . David's idea is along the same lines, but even a non-techie will immediately grasp Walter's. . . [1] Very easy.

*Cough* Alternate plasma/no plasma on the spark gap sounds (and behaves) "active" in my opinion. ;-)

Tim

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