Need help with sorta basic circuit

Discussion in 'The Projects Forum' started by zack501, Dec 2, 2010.

  1. zack501

    Thread Starter New Member

    Dec 2, 2010
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    Hi. Im building a circuit for my project at school. I'm only 17 and my lack of electronics knowledge probably shows lol. i had some basic electronics in AP physics and i took two electronic classes at the college this year and thats all i have. anyway, i have attached a copy of the what i have gotten so far. I am wanting to use a 9v battery to power a coil of a TPDT relay (not on the schematic that i attached but will be in parallel with everything else) but also in the circuit i want to have a bi-color 2-lead LED which is green when the switch is closed and when the switch is opened i want the capacitor to power the red for a short period of time. I have gotten it to do this in multisim with the design have however, as i said before, i know little about electronics. For one i wanna know if there is possibly a better way to accomplish this? and i also want to know if it would even work? I know the capacitor in the circuit is probably incorrect i just picked one to try and get it to do what i needed it to so i was wondering which to use. i also have two Schottky diodes in the circuit to stop the relays from just switching on and of instantaneously. i dont know anything about diodes really besides that they only let current travel in one direction but i dont know how they affect the circuit overall. will they work? and which should i use. I noticed in simulation with the addition of diodes the capacitor charged less rapidly but also caused it to discharge slower. I only want the red LED to stay on for like 10 seconds or so. And as far as amperes go. with the setup i have, the amps are very high at first, way to much for a 9v battery, and not that low after a period of time either. I assume the type of capacitor and diodes use affect this greatly and i know i could add some resistors to get the total resistance up and the total amps down (im not exactly sure where they would be placed lol but im sure i could figure it out) and one last thing, I dont want the capacitor to take an hour to charge enough to run the led for 10 secs. Ok i know this is a ton of information and i apologize lol but please help
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    I got lost in the description.

    What do you want the LEDs to do? Flash in a certain order, fade in, fade out, etc? Start with that, and we'll go to a circuit from there.
     
  3. zack501

    Thread Starter New Member

    Dec 2, 2010
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    when the switch is closed i would like the green LED to be illuminated. When the Switch is Open i would like the red LED to be illuminated for a short period of time by the capacitor. I have gotten the circuit to do that with the way it is now though. And if it would be easy i would like just the red LED to flash for the short period of time that it is on
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    A capacitor cannot light an LED for any appreciable amount of time. How long were you wanting to have the LED lit after the switch is open?

    The timing and blinking can be from Bill Marden's blog on 555 Timers

    Is it possible to use a SPDT switch for the LEDs? This would simplify the circuit a good deal.
     
  5. zack501

    Thread Starter New Member

    Dec 2, 2010
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    You mean use a SPDT switch instead of the relay so that when the switch is open the capcitor send charge the appropriate way to light the red led? and not long at all. like 10 seconds. maybe a little less
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    Please restate what you want, not how you want to do it. :D
     
  7. zack501

    Thread Starter New Member

    Dec 2, 2010
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    I want to have a circuit with a roller microswitch and a bi-color 2 lead LED. When that microswitch is closed i want one color of the LED to illuminate. when that microswitch is then opened i want the other color of the LED to light up for a short period of time and also blink. And I am hoping to be able to use a 9V battery if possible
     
  8. thatoneguy

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    Feb 19, 2009
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    My ideas have pretty much gone directly to a 12F683 PIC uC for a solution, but trying to stay with discrete parts, I had the following rough outline of an idea:

    When the switch is closed, the Green LED is lit, and it also charges a cap on pin 4 of a 555 (shown Here that doesn't show the capacitor, just the concept of enabling/disabling the timer.

    Once the capacitor is charged, the 555 will oscillate (blink the LED) until the cap on pin 4 is discharged (delay). There would be one additional requirement of disabling the Red LED while the green one is on.

    What are the expected on and off times for the switch, not much can be designed without that knowledge?

    Using a SPDT roller switch would simplify this a lot though.
     
  9. zack501

    Thread Starter New Member

    Dec 2, 2010
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    Uhm I'm not exactly sure. It will vary. I think as far as designing the circuit goes we can assume it will be on for 5 minutes. And I would like to use some sort of microcontroller unfortunately I do not have the knowledge. However I have been reading up on them and trying to teach myself
     
  10. thatoneguy

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    Feb 19, 2009
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    How long will it be off for after roughly 5 minutes of being on? How many seconds would you like the LED on after the switch changes positions, and how fast of blink, 10 per second, 2 per second, etc?
     
  11. Wendy

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    Mar 24, 2008
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    I think could do this with one 555 and a couple of transistors. However it is going to take a little while to draw up if I do it.

    I think one guy as the right of it though.

    The base concept is from my LEDs, 555s, Flashers, and Light Chasers article, chapter 4 circuit #1.

    [​IMG]

    The extra parts would be there to prevent the second LED from lighting while blinking.
     
  12. zack501

    Thread Starter New Member

    Dec 2, 2010
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    It only needs to be on for like 10 seconds. And maybe 4 Times a second
     
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