game Show control

Discussion in 'The Projects Forum' started by lespaul, Feb 10, 2011.

  1. lespaul

    Thread Starter Active Member

    Jan 30, 2008
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    I know this has been out there before, but needed some help.I just built this circuit with LED's instead of incans for the indicator lamps. I also used a 5.1v zener instead of the 9v. It works, however, it will not lock out the other lights when the buttons are pushed. its like I can push the buttons and all three lights come on. The lock-out option doesn't seem to be working. below is the link to the circuit...any thoughts?

    http://www.techlib.com/electronics/games.html
     
  2. lespaul

    Thread Starter Active Member

    Jan 30, 2008
    49
    2
    OK, an update...i switched out the led's and current limiting resistors for 6V incandescent bulbs and now the circuit works. So, why won't this lock out the other SCR's using LED's??

    I need to make this simple circuit work on a bigger scale. I would like to be able to control a solid state relay or LED driver. I need the output to control a much brighter LED's (3watts or better)
     
  3. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
    230
    I've built several versions of that. It could be that with the LED/resistors, there isn't enough current through the SCRs to allow them to latch ON. What SCRs are you using? Can you post a schematic of exactly what you did in the LED version?

    Ken
     
  4. lespaul

    Thread Starter Active Member

    Jan 30, 2008
    49
    2
    Hey Ken...its basically the same circuit only I substituted the 9V zener for a 5V zener and added three 2.6V leds. The led's are in series with the cathode of the scr along with a 1k current limiting resistor. The circuit latches the leds 'on' just fine, but will not lock-out any of the other switches when they are pressed. I am also running my supply voltage at 9v and using S401 scr's. I need this to be a 'first switch' block the rest type of function. kinda stumped here. I may have to abandon and go logic instead, but needed to get this up and running today.
     
  5. lespaul

    Thread Starter Active Member

    Jan 30, 2008
    49
    2
    attached is a quick sketch of the revisions I made to the original schematic. \

    http://www.stagingsolutions.net/published/WG/show.php?q=NTEwODU4VEVTVA==-62779b52[/IMG]
     
  6. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
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    The schematic tells the tail. :( You would need an LED and resistor, in series between the top of the + terminal of the battery and the cathode of the Zener. This is like the left-most lamp in the original circuit. The idea is that the two lamps, or pairs on the LESs/resistors, divides the 9V in half so there in not voltage for the Zener to conduct and the other SCRs cannot be triggered.

    Ken
     
  7. lespaul

    Thread Starter Active Member

    Jan 30, 2008
    49
    2
    OK, I see what you mean. trick now is to find the right led/resistor combo to make this work...divide the 9v. Obviously, a 1K and the 2.6V led will not work.
     
  8. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
    230
    From the datasheet, the S401E requires 30mA (Ih) to latch. With two 2.6V LEDs at 30mA current and a 9V supply you would need a ~68Ω resistor in series with each LED. (9V-2.6V-2.6V)/0.03A=157Ω 157Ω/2=78.3Ω....so a standard value=~68Ω

    Ken
     
  9. lespaul

    Thread Starter Active Member

    Jan 30, 2008
    49
    2
    Thanx Ken...that works quite well. I may work on changing out the LED's for 2N222's to drive a relay or solid state relay. At some point I need to drive much brighter LED's for podium displays. I have 5 podiums with front mounted LED's that are controlled by a 12v @ .5A OEM driver.
     
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