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Help with "switch box" halloween prop (2leds + solenoid)

Discussion in 'LEDs and Optoelectronics' started by sieg, Oct 16, 2015.

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  1. sieg


    Oct 16, 2015

    I am making a couple of props to use in an "escape room game" for my halloween party.
    To open this box, a solenoid will release a tab, so the lid can be opened.
    I wired 20 switches so that the circuit is closed by a certain combination of switch positions and the solenoid opens the lock.

    When you insert the key in the square hole, a switch is pressed and the "key OK" led lights up. I got things working up to this point, but then I overestimated what I knew about electronics (which is not a lot at all...)

    The "key ok" led lights up when you insert the key, but I would then like the solenoid to be powered (it's rated 3v to 12v) and a second led to light up when the 20 switches are all in the right position. The problem is that I can get the first led to light up, but the second led and solenoid do nothing at all (switch positions are correct)...
    I briefly tried the second led without resistor + solenoid as a test, which kind of worked, but the solenoid seemed to be underpowered. Can the solenoid's internal resistance replace the led's resistor?

    Power source = 6V (I can change this if needed)
    The leds both have a forward voltage of 3V and 20mA current. I used 2 150Ohm resistors, could this be the problem? Maybe the leds + resistors "used up" all the available power so the solenoid is left underpowered?

    Does anyone have any idea what I could do make this circuit work so the solenoid opens the box? Does the left part of the circuit maybe interfere with the right part, or does it seem like a valid parallel circuit?

    I have added an image of the box and the circuit I used.

    Thanks in advance! Screen Shot 2015-10-16 at 14.43.18.png box.jpg
    Last edited: Oct 16, 2015
  2. Martaine2005


    May 12, 2015
    Hi Sieg,
    Your diagram shows an led switching the solenoid,. At best, the solenoid is getting 25ma and 3v. You are probably better to have the solenoid switched on after S2 (not through the led) and maybe a 9v battery.
    I could be wrong!!! Normally am!!

    Great use of switches though! Nice idea.

  3. BobK


    Jan 5, 2010
    You want the second LED and the solenoid in parallel, not in series.

  4. sieg


    Oct 16, 2015
    I copied the circuit on a breadboard (my first breadboard ever - no more cutting resoldering and restarting every time I'm "sure" it will work this time :p ) I'm going to try this right away. Thanks for the help!
  5. sieg


    Oct 16, 2015
    It absolutely works perfectly, thanks again!
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