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Anti-thyristor?

Discussion in 'General Electronics Discussion' started by georgetheman, Sep 14, 2013.

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  1. georgetheman

    georgetheman

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    Sep 14, 2013
    Is there a device that could operate like a thyristor, but disconnecting a circuit instead of completing it. I have tried using a relay, but it is preferred if the circuit/device could operate without the added power drain.
    :confused:
    ------GeorgeTheMan:D
    Edit: I am basically trying to disconnect one monostable-astable pair, and start another pair after the first has finished. + I am noob
     
  2. duke37

    duke37

    5,364
    772
    Jan 9, 2011
    It seems that you wish to switch a low power signal. A transistor will do this.

    Show us a diagram of the parts you wish to switch and your working relay solution so that suggestions can be made on how to do it. It may be preferable to inhibit one circuit rather than disconnect it.
     
  3. georgetheman

    georgetheman

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    Sep 14, 2013
    lel.PNG
    Although the circuit functions perfectly, I would like it to, once the first pair has finished, to turn off that said pair, so all of the current goes into the second pair.
    Capture.PNG
    The Method with the relay poses another problem, although working, it is a power drain, and i need the power for another part of the system I am adding.
    Thanks
    -GeorgeTheMan
    Edit: It would be preferred if the anti-thyristor circuit/device could go where the relay is, having the trigger being after the initial thyristor, without the added issue of being a power drain.
     
    Last edited: Sep 14, 2013
  4. georgetheman

    georgetheman

    7
    0
    Sep 14, 2013
    Update: I've added the part of the circuit mentioned before, but, this means that both monostable circuits need to be turned off after use. :/
    -GeorgeTheMan

    sdcs.PNG
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    What are you using to draw this schematic?

    What is common with all the diagrams I've seen drawn with it is that some normal conventions aren't followed. I'm pretty sure it's the people using it, nit the software.

    Generally when you're drawing a schematic, you don't add more wiggles in lines that you have to. The extra wiggles are a distraction.

    [​IMG]

    I've circled the needless wiggles in red.

    Another issue us where you have parallel lines that are actually connected. In almost all cases, you should just stick to a single line. This is even more confusing than the extra wiggles. I've marked these in green.

    And then you have some obvious design issues. I have marked these in magenta. There are cases where you seem to be needlessly using diodes, other places where you appear to bias transistors in a very unusual way, and plenty where you provide no limit to the base current.

    Not highlighted are components drawn unconventionally (upside-down transistors), superfluous power supply lines, a general structure that doesn't flow from left to right, etc.

    The end result is that your circuit is far harder to analyse than it should be.

    If the tool you use is freely available, and you can send me whatever is needed so I can edit your circuit, I can try to straighten it out for you.
     

    Attached Files:

  6. georgetheman

    georgetheman

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    Sep 14, 2013
    At this moment, my school has provided all of the students with a copy of circuit wizard 2 student edition, which i have also provided for you. The basics of the circuit are that there are two monostable astable pairs, and when the first has finished, the second is activated, but, when the second is activated, the first pair, needs to be rendered useless, and so, the system cannot be reset.
    I have also linked the edited version of the Circuit, including the changes from Steve (thanks, its much simpler and cleaner to understand now). Thanks for all this help!

    eerytiuop.PNG

    Circuit Wizard 2:Student Edition:
    [REMOVED]

    My Circuit:
    http://www.mediafire.com/download/hhlyjnt9c23rcb9/CircuitAlpha3.rar
     
    Last edited by a moderator: Sep 15, 2013
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    OK, that's not a demo version, so I've removed the link.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    OK, here is an improved layout. It's logically the same as the one you drew, but I'm pretty sure you'll agree it's a lot easier to read.

    I can also tell you it won't work.

    [​IMG]

    Notice that you're using two NAND gates wired as inverters and two inverters. This is a waste. Either use 4 NAND gates (there are 4 in a package) or use 4 inverters (there are 6 in a package).

    Also note that you have used electrolytic capacitors for all the capacitors. I have changed one for a non-polarised capacitor, you should do the same for all the low valued capacitors.

    Also note that I have lined up all the capacitors and resistors (it just looks tidier).

    I increased the spacing between your +ve and negative rails. I probably could have made them even wider. There is never any good reason to cramp yourself.

    You also had resistors horizontally at the ends of the power rails. I've turned them around to point vertically.

    Oh yeah, I staggered the 555's a little more so you can have straight lines with fewer wiggles.

    And now the circuit flows from left to right. At a glance, you can see what it's kinda doing.

    Oh, and I've changed the page layout to landscape. A3 would be even better. I had to squeeze it up a little horizontally to fit it on A4.

    What you need to do

    The logic and the transistors make no real sense. What are you actually trying to achieve?

    Using SCRs also seems pointless as they will lock on after they're turned on. Maybe that could make sense for the first one (D6?), bit not for the other one.

    So, you need to explain what you want the circuit to achieve. I suspect that you will end up with fewer logic gates, and no SCRs (but maybe a mosfet or two)
     

    Attached Files:

  9. georgetheman

    georgetheman

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    Sep 14, 2013
    Thanks for the re tweak of layout, its better than i could have dreamed!
    The circuit is a simple alarm circuit.
    Basically, after the first monostable-astable pair has completed, the thyristor (SCR) enables the second circuit, (or should). After the reed switch is triggered, the second pair should activate, giving the user 5-10 seconds to enter, otherwise, a siren (played by the buzzer) should sound, until a key switch turns it off.
    At the moment everything is fine and dandy, but for the alarm system to be functional, the first monostable must be turned off, or at least deactivated in order for the second to be triggered, as to avoid resetting the alarm.
    Thanks for all this help, without it, i probably would have already scrapped this alarm system.
    -GeorgeTheMan:D
     
  10. georgetheman

    georgetheman

    7
    0
    Sep 14, 2013
    Update: I am thinking of a different method to deactivate, but this would require an electronic version of a single pole double throw switch., If anyone could provide such device, this would be greatly appreciated.
    -GeorgeTheMan:D
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    The question you need to answer is "what in the circuit is supposed to turn the first SCR on?

    Is it IC1 output High and IC2 output Low? Because at the moment you seem to be taking a really complex path to get there. At 9V, you're likely to destroy Q2 and Q3 eventually as you reverse bias the Base-emitter junction at a voltage that is likely to make them break down.
     
  12. georgetheman

    georgetheman

    7
    0
    Sep 14, 2013
    The scr is suppose to activate the second circuit when the first has finished. I know that the circuit doesn't make any sense, but somehow, I have managed to turn on the second circuit with the transistor pairing. I have tried other methods, but all have been rendered useless. If there is any input on how I could get that working, I would be very great foul,
    Thanks
    -GeorgeTheMan
     
  13. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    In order to do that we need to know what is meant by "finished".

    I could work it out, but this is homework. Whilst I'm quite happy to show you how to draw your circuit in a way that is readable, I'm not going to figure out what's wrong with it and fix it. That's your job.

    You need to tell me what levels on the pair of 555's indicate that the first circuit has "finished" and what you need to do to the SCR to turn it on.

    Then we can talk about how we might do that with transistors or digital logic.
     
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