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Breadboard exam

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  • 27-05-2017 2:18pm
    #1
    Ryanh989
    Registered Users Posts: 3 ✭


    Hey everyone, i have an exam coming up in my phase 4 and i have to wire up and explain a breadboard circuit.

    This circuit is the following:
    ibb.co/dh45Ca
    (Just put http:// infront of that link as im a new user iy wont let me post the link!)

    I have tried it at home however im not sure if im doing it correctly does anyone know what is meant to happen?


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    #2
    Michael Collins
    Moderators, Science, Health & Environment Moderators Posts: 1,850 Mod ✭✭✭✭Michael Collins


    What happens with the circuit you've built at home?


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    #3
    my3cents
    Closed Accounts Posts: 9,764 ✭✭✭my3cents


    Ryanh989 wrote: »
    ... does anyone know what is meant to happen?

    I think there is more than a hint in the title

    Project 7 Time Delay Circuit


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    #4
    Ryanh989
    Registered Users Posts: 3 ✭Ryanh989


    Michael Collins wrote: »
    What happens with the circuit you've built at home?

    Well, bith lights were on all the time and once i shorted the capacitor all that happened was that they dimmed a little, i assume the red light is on and once i short the capacitor the green then comes on? Im not sure im fairly sure i have wired it correctly!
    my3cents wrote: »
    I think there is more than a hint in the title

    Project 7 Time Delay Circuit

    Okay thanks for your input, not.

    I was looking for more of a technical explanation as to what the capacitor & transistors function is.


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    #5
    my3cents
    Closed Accounts Posts: 9,764 ✭✭✭my3cents


    Ryanh989 wrote: »
    Well, bith lights were on all the time and once i shorted the capacitor all that happened was that they dimmed a little, i assume the red light is on and once i short the capacitor the green then comes on? Im not sure im fairly sure i have wired it correctly!



    Okay thanks for your input, not.

    I was looking for more of a technical explanation as to what the capacitor & transistors function is.

    It took me a few seconds to google the title for a near full explanation of the circuit along with a video of it being made and working on a breadboard. So I gave a reply commensurate with the effort you seem to have put in so far.

    I say near full explanation as most of the explanations of that capacitor timer circuit only have the one LED connected to the transistors emitter.


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    #6
    Ryanh989
    Registered Users Posts: 3 ✭Ryanh989


    Not sure where this 'lack of effort' statement has come from, you do not know me nor my efforts to try and solve my problem, no matter what circuit i followed on youtube or the internet in general would not work. Spent a couple hours between today and yesterday trying to solve it.

    I finally got it right this moment, i decided to try a different transistor and it worked a dream!

    So my initial transistor was faulty!

    I now will have to explain what is happening in technical terms which im not sure how to state.

    So what im thinking is, once a power is applied to the circuit the red LED emits light, the base opens the switch on the transistor from the collector to the emiter the green LED will not light once the capacitor is fully charged but once the capicitor is shorted via the shorting switch the capictor begins to charge allowing current to flow to the Green lED.

    Would that be a suffiecient explanation?


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    #7
    brightspark
    Registered Users Posts: 2,637 ✭✭✭brightspark


    Ryanh989 wrote: »
    Not sure where this 'lack of effort' statement has come from, you do not know me nor my efforts to try and solve my problem, no matter what circuit i followed on youtube or the internet in general would not work. Spent a couple hours between today and yesterday trying to solve it.

    I finally got it right this moment, i decided to try a different transistor and it worked a dream!

    So my initial transistor was faulty!

    I now will have to explain what is happening in technical terms which im not sure how to state.

    So what im thinking is, once a power is applied to the circuit the red LED emits light, the base opens the switch on the transistor from the collector to the emiter the green LED will not light once the capacitor is fully charged but once the capicitor is shorted via the shorting switch the capictor begins to charge allowing current to flow to the Green lED.

    Would that be a suffiecient explanation?


    Like others here I don't want to give you the answers more point you in the right direction.

    Well done on determining that you had a faulty transistor, did you test it or just guess the part was faulty?

    Fault finding will probably be a very important skill in your future career, even if you only work in the domestic sector you need to be able to work out what is supposed to happen and why it isn't happening!

    You need to rethink your explanation, does a shorted capacitor charge?

    Think about how the capacitor charges, and how that affects the current flow in the transistor and how that affects the current in the diodes.
    (Work out the voltages and currents for a fully charged capacitor, a shorted capacitor, a freshly discharged capacitor and perhaps at a mid charge?)

    You should be aware of the relationship between the capacitor and resistor and how that affects charging. There is as I recall a formula involved, think about what would happen if you use a different capacitor or resistor etc.


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