Connect with us

Beginner in need of Help!

Discussion in 'Electronic Components' started by James, Jan 9, 2007.

Scroll to continue with content
  1. James

    James Guest

    --------
    -----O O-----

    Can anyone tell me what I would need to produce a component that acts as a
    switch - switching either on or off according to how much voltage is going
    through the circuit?


    James
     
  2. Be more specific.







    --
     
  3. Fredrik

    Fredrik Guest

    If the it's DC-current and voltage below 30V, you can use a comparator.
    http://www.national.com/pf/LM/LM111.html

    Find a point in your cuircuit where the voltage vary with the current and
    connect it to one of the inputs. (If you can't find any put in a low value
    resistor serial.)
    Connect a fix voltage to the other input and you will have your signal on
    the Output switching between open and ground depending of the current.

    Good luck /Frederik
     
  4. As Fredrik said, look at a comparator. (Or any cheap standard op-amp).

    Also, look at discrete active components, the transistor, FET, thyristor
    and triac. Any one of those might be suitable. By the time you understand
    each of those well enough to choose the most suitable and apply it to your
    problem, you won't be a beginner anymore. it won't take you very long to
    work it out either, the more references you find online and can grasp
    quickly (pass over those that look opaque, there are are always other
    opinions and guides), the faster you'll grasp the rest and know which ones
    are useless to you.
     
  5. James

    James Guest

    What I want to achieve is hard to describe but I'll try. Say I've got a v
    simple circuit that includes a power supply and a bulb. I break the circuit
    and want to put something in its place - this component would measure the
    voltage and, providing it was in-between set boundaries (i.e. between 0.4V
    and 1.2V or between 2.4V and 2.8V) would complete the circuit. If the
    voltage was not within ranges specified, the circuit would remain broken. I
    hope this is clearer :eek:)

    James
     
  6. How can it sense the voltage without applying voltage?







    --
     
  7. Graham W

    Graham W Guest

    Is this something to do with cycling ni-cads for RC Models?
     
  8. Jamie

    Jamie Guest

    you need something called a voltage comparator.
    look it up.
    they come in various forms.
    the LM311 is a comparator that works ok.
    op-amps also can work as a comparator how ever,
    some op-amps have full backs depending on how
    complex you get and what you expect over all.
     
  9. ehsjr

    ehsjr Guest

    ______
    V+ ----A B-----+
    |
    [Bulb]
    |
    Gnd --------------+

    What you described means the circuit must sense
    the voltage between points A and B. You *don't*
    want to do that - your description is not correct.
    Every time you close the contacts that connect A to B
    the voltage between them drops to 0 and your sense
    circuit can no longer determine whether the contact
    should remain closed or should open.

    What you *do* want to do is sense the voltage between
    V+ and ground. When that voltage is within a specified
    range, you want points A and B connected.

    You can use a window comparator to meet the above
    requirement. I think you want more detail than just
    the words "window comparator", but more detail on the
    requirements is needed to do that. What is the load
    current? What is the maximum range of V+ ? What
    are you trying to do? Someone replied suggesting
    you might want to discharge a NiCd - if that is the
    case, say so.

    Ed
     
  10. James

    James Guest

    What I really want to do is be able to send a digital signal (via means of a
    series of switches on a control box) through a series of parallel circuits
    each containing one lamp. Each corresponding signal or absence of a signal
    (data) would then either allow or not allow power to the lamp (power.)

    see
    http://homepage.ntlworld.com/james.merrie/educational/physics/electronics/el
    epic.jpg

    Is the need for a digital set of electronic pulses what differentiates a
    digital electric circuit from an analogue electric circuit? How can this be
    accomplished with this circuitry?

    I hope this is clearer


     
  11. From my earlier post:

    Look at discrete active components, the transistor, FET, thyristor
    and triac. Any one of those might be suitable. By the time you understand
    each of those well enough to choose the most suitable and apply it to your
    problem, you won't be a beginner anymore. it won't take you very long to
    work it out either, the more references you find online and can grasp
    quickly (pass over those that look opaque, there are are always other
    opinions and guides), the faster you'll grasp the rest and know which ones
    are useless to you.

    Specifically, look at the use of an NPN transistor on the ground side of
    each load (lamp, in this case). It's a cheap, easy, standard method of
    making a small signal (digital or analog) control a low-voltage DC load.
    Look at the use of a transistor as switch, rather than as gain stage.
     
  12. ehsjr

    ehsjr Guest

    You want an X-10 system. Google X-10.
    It works by placing digital addresses and
    commands on a 121 kHz signal which is placed
    on the AC mains.

    For your other question:
    http://en.wikipedia.org/wiki/Digital

    Ed
     
  13. If you just want several switches to individually operate several
    lights, (switch one turns on light one, switch two to light two...)
    there is no logic required - just connect each switch in series with
    its corresponding light, and connect all the switch/light pairs in
    parallel across the power supply - see
    http://members.shaw.ca/peterbb/sw-light.gif

    --
    Peter Bennett, VE7CEI
    peterbb4 (at) interchange.ubc.ca
    new newsgroup users info : http://vancouver-webpages.com/nnq
    GPS and NMEA info: http://vancouver-webpages.com/peter
    Vancouver Power Squadron: http://vancouver.powersquadron.ca
     
  14. No. Are you trying to build a "Magic Switchboard"?








    --
     
  15. James

    James Guest

    I need all the switches to be located in one place
     
  16. James

    James Guest

    Does such a component exist?
     
  17. Mikkel Lund

    Mikkel Lund Guest

    James skrev:
    Yes, get it at the Magic Shop.
     
  18. James

    James Guest

    haha

    If you looked more closely, you'd see I was after a circuit that would be
    able to handle digital signals.
     
  19. We looked plenty close, and gave you a magic potful of wrong answwers.
    What's really funny is none of us are to blame. You're going to have to
    spill the whole story of what you want, partly to frame the concept to
    yourself so you have a clearer idea of what to ask, then to ask so you get
    meaningful answers. So far you've been suggested a set of switches in
    paralel, through transistors, op-amps and comparators, and a full-scale
    digital system modulated onto the AC line, and we don't even know if you're
    wanting your mains lamps switched, or a set of torch bulbs on a wodden
    board for an educational project, because you won't tell us. And unless you
    do, people will start to wonder if you're a troll baiting people into
    looking like fools by sounding like they know the answer to a question that
    was never really asked.
     
  20. Please "bottom post" - place your reply below the message you are
    replying to, and trim any unnecessary quoted material - thanks.

    So - put all the switches and the power supply in one place, and run a
    pair of wires (power from switch, and return to supply) to each light
    - no electronics required. If all the lights are in one place, a
    single return wire may be adequate, depending on the current drawn by
    the lights, and the operating voltage.

    If you have something more complex in mind, please give us more
    details of your requirements. The better you specify the problem, the
    more likely we will be able to give a useful answer.

    How many light/switch pairs are there?
    Are all the lights also in one place?
    How far from the switches to the lights?
    What type/voltage/power are the lights?



    --
    Peter Bennett, VE7CEI
    peterbb4 (at) interchange.ubc.ca
    new newsgroup users info : http://vancouver-webpages.com/nnq
    GPS and NMEA info: http://vancouver-webpages.com/peter
    Vancouver Power Squadron: http://vancouver.powersquadron.ca
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-