What do you understand from this schematic??

Discussion in 'The Projects Forum' started by rokz_2005, Jul 12, 2011.

  1. rokz_2005

    Thread Starter Member

    May 14, 2011
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    Ok I know what it does but can some one tell me what the values of each of the components are. the only thing that i recognise is the capacitor symbol. What are the rest of them?? (I appreciate your help in advance) Thanks
     
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Doesn't that look more like PLC ladder?

    In my opinion the "capacitors" are inputs, enabling a one-shot timer which in turn enables the output.

    Since I'm not a PLC programmer I could be totally wrong though.:D
     
  3. KJ6EAD

    Senior Member

    Apr 30, 2011
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  4. rokz_2005

    Thread Starter Member

    May 14, 2011
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    Thanks for the reply.
    I am after the feature of this circuit but have no idea at all on how to build it. Is this part of an ic or just a few components stuck together?
     
  5. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    The waveform diagram shows inputs going 'high'. The method used could vary. Relays, transistor switches, or similar are all possibilities.
    'TD1' is used twice with two different symbols. Could be 'time delay', or something else.

    This is NOT a component level schematic, but is what we call a 'block diagram'.
     
  6. mbxs3

    Active Member

    Oct 14, 2009
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    Definitely ladder logic.

    The TD symbol that is a circle is probably as Kermit stated, a Time Delay Relay, but the circle TD1 represents the relay coil.

    The TD1 that is in the 2nd rung is the normally closed, timed open, contact of the Time Delay Relay. This contact is closed when the relay coil is de-energized and delays in opening when the coil is energized.

    The symbols that resemble capacitor symbols in normal schematics is representative of a switch of some sort. It could really be anything, from a pressure switch to a toggle switch. In this case, they are both normally open switches.

    A general breakdown of how this particular circuit would work is this:

    We will assume that the "input" is a toggle switch.

    When the toggle switch is set to on, the time delay relay coil is energized. At the same time, the output(a light bulb or LED in this case) is energized through the closed TD1 contact as well as the closed input(toggle switch) contact. After the 1 second time delay, the TD1 contact on the 2nd rung opens, de-energizing the output(light).

    The waveforms at the bottom of your schematic, as Kermit also noted, are the states of the circuit in regards to being on or off, high or low, 0 or 1, etc.

    Are you taking a PLC course?
     
  7. mbxs3

    Active Member

    Oct 14, 2009
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    This is a circuit you would see in programmable logic controllers which are usually used in an industrial setting. PLC's use "ladder logic" to explain the way a circuit operates. Ladder logic is read rung by rung. In the case of your schematic, there are only 2 rungs. Although you could easily build this circuit, you would usually not use "ladder logic" to illustrate your schematic unless you were in a PLC setting.
     
  8. mbxs3

    Active Member

    Oct 14, 2009
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    Also, ladder logic, just like a block diagram, is not very informative of the component specifications, but rather a tool to easily show circuit function and signal flow, etc.
     
  9. rokz_2005

    Thread Starter Member

    May 14, 2011
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    Hey guys, thanks for the information, its been super helpful. I wanted to integrate this to an LED. Which components would I need to build this?
    Is there a name for these kind of circuits which I could look into?


    (PS i'm not studying PLC)
     
  10. rokz_2005

    Thread Starter Member

    May 14, 2011
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    I may have fond the answer. Pretty close to this.

    See pic, (got this from http://www.falstad.com/circuit/e-multivib-mono.html )

    Can someone confirm that the components used in this circuit are..
    1 switch
    5 Resistors
    1 capacitor
    3 Transistors (I have bc547 - Can I use that?)
    And i'm guessing that when I change the value of the capacitor my out put pulse can be controlled?



    Thanks
     
  11. mbxs3

    Active Member

    Oct 14, 2009
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    A little more description of what you are trying to accomplish would help greatly. In theory, all you need to light up an LED is a power source, resistor, and the LED.
     
  12. rokz_2005

    Thread Starter Member

    May 14, 2011
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    I wanted to build a circuit without the use of iC's to create a pulse no matter how long the power (switch) was turned on for. So for every time the power came on (whether it is for ms or s) the output would always be the same E.G Led turns on for 10s

    I' ve got the answer via another thread. even though the 2nd schematics does not conform to the original in and output, this will do :)
     
  13. castley

    Member

    Jul 17, 2011
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    what about a relay with a normally closed contact? The capacitor charge thru the relay coil holds the contact open for one second. The incoming pulses must be long enough to fully charge the capacitor.
     
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