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Basic Project Selection

Discussion in 'Electronics Homework Help' started by Armored2DaCore, Mar 15, 2011.

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  1. Armored2DaCore


    Mar 15, 2011
    I am in a high school Digital Electronics class (Project: Lead the Way) and am trying to select a final project. I have a very basic understanding of Digital Electronics as a whole, but I catch on quick and want to do something a little more advanced as a final.

    These are some of the things I have been thinking of:

    • A digital clock using crystals from a motherboard
    • A 8-digit calculator with keypad
    • A spark-gap generator (Jacob's Ladder)
    • An electric guitar amp
    • A constant tone generator with a dial to select pitch

    Can someone give me an idea which of these (if any) is within the skill set of a novice such as myself? I am also open to suggestions.
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Well, firstly, only the first two are really related to digital electronics.

    The digital clock would be the easiest of the top 2 options, although definitely non-trivial.

    If you're going to re-use parts from a modern motherboard then you had better be willing to work with surface mount electronics!

    A clock consists mostly of dividers, counters and display drivers. All digital electronics, and reasonably straightforward without being totally trivial.

    The second option would require a microcontroller and lots of programming, or more logic than you could shake a stick at. Floating point arithmetic is definitely non-trivial and 90% (or more) of the work involved (if using a uC) would be only slightly related to your class work.

    Just my opinions though. Maybe you should ask the same question of your teacher?
  3. Laplace


    Apr 4, 2010
    When I was in high school electronics I built a combination of your first and last selection: a tone generator controlled by a 10-turn potentiometer with a built-in LED display frequency counter on a timebase derived from a crystal oscillator, all in a handheld box. Back then all we had were regular TTL chips. The box was filled with layers of proto-board packed tight with TTL chips. When I first powered up the box, it only took a few minutes before the box was too hot to hold. That was my first lesson in heat generation and transfer.

    Another project I built in that class was a spark gap generator (Tesla coil) powered from a 15,000 volt neon transformer. Wound the secondary coil on a 4 ft plastic sewer pipe, and built up a glass plate capacitor. It was spectacular, generating 12" discharge from the top of the coil. I heard the story when the teacher was demonstrating this device to another class and pointing out the operating components, he let his hand get too close to the secondary coil and drew the discharge into himself. He was saved from being fried when he collapsed to the floor since the Tesla coil was up on the bench. But this was before I had any understanding of coupled resonant circuits. If I had that knowledge back then, I could have tuned the Tesla coil for even better performance!
  4. Armored2DaCore


    Mar 15, 2011
    Thank you very much for the advice. I'm probably going to go with the clock, as the majority of the components are readily available. Asking my teacher is unfortunatly not much of an option as he is new this year, and doesn't really know what he's doing yet. The book we have is doing the majority of the teaching, but thats ok because the learning is getting done either way. Thanks again for the help.
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    One of the trickiest parts will be providing some way to set the clock.

    Unless you use counters that can be made to count down, the best way may be having some method of allowing hours, minutes, and seconds to be independently reset and incremented.

    If you think about it for a while, I'm sure you can come up with something that won't involve masses of logic.

    edit: And on that point, consider powering the display section independently of the oscillator/counters. If you do that then you can have some form of backup power to the oscillator/counters which will allow you to remove power and not have to reset the clock. This may be a very useful thing for a project as it is likely going to be unplugged, and moved around a bit, and you really don't want to be resetting the time all the time!

    If you do this (and I guess it depends on your skill level and the amount of time you have) then you will have to consider the issues of having powered logic devices connected to unpowered devices. tristate outputs and/or logic families allowing active inputs when powered down are options.

    Also you would be definitely looking at CMOS for anything running from battery backup (and it will also nicely get around the issue Laplace related about power consumption of TTL (and to a lesser extent LSTTL)
    Last edited: Mar 17, 2011
  6. Armored2DaCore


    Mar 15, 2011
    I spoke with my teacher and described the level of complexity building the clock would involve. He told me that if I was to create a working model in the Electrical Design Software we are using (MultiSim 10), he would give me full credit, even if i didn't physically build the clock. It is certainly the more economical choice in terms of time and money, and I am good with the software. Overall this seems like a good idea, but I sort of want to walk away with something tangible.

    My teacher also said that if I could reduce the complexity, like make it count down from 1 min and then reset, not a full fleded clock.

    I've no idea what to do here.
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