Flickery Flame - 3 kits in serial? Powered by AC?
  • Hello,

    I have a pinball machine that has a backglass feature that is perfect for some flickery backlighting and someone created something similar to a Flickery Flame kit and wired it to their pinball light circuit.  That person was supposed to be building kits for people, but as of a year ago, he has fallen silent.

    I got to thinking about what it would take to reproduce something similar, and it dawned on me that 5 years ago, I bought a Yule Log fire sim LED kit from RadioShack and had never assembled it.  I put it together and it sort of works for the backglass feature, but runs on 4 AA batteries, so 6V. But the board is a bit oversized and I would actually need 2 additional kits to wire in serial for the full effect I am after.  The instructions mention you can wire up to 3 in a row so, I look up the yule log kit and it is no longer to be found anywhere online.

    This led me to finding the Flickery Flame kit which looks to be the perfect size for my needs.  My questions are:

    1) Can I wire three flickery flame kits together in series and use one battery pack?

    2) If yes for #1, can I wire all three from a) one battery back OR better yet b) convert it to AC for use in the pinball general illumination circuit?

    The standard #44 bulb for a pinball backbox general illumination is 6.3V with .25amps.  A slightly lower powered #47 bulb is 6.3V with .15amps.  I would love to be able to have this just power on with my game.  Is there a way?

    The RadioShack kit has a miniswitch that I considered running long wires to the coin door and operating the switch manually, if I can't figure out a way to wire it into the game, but I'd prefer an in-circuit solution.

    My kits should arrive this week and I'm hoping it's possible to do what I'm after with these kits.

    Thank you!


  • The flickering LEDs cannot be used in series, nor directly driven by AC. Think of the processor in each LED as being a bit like a computer-- when you remove power (whether that's by switching it with AC or by putting it in series with an LED that blinks off its power), it reboots, and never gets to run its flickering program.

    However, there are some good ways to get the basic result that you are after. For example, one flickering can be used in series with one or more non-flickering LEDs, and will cause all of the LEDs in that series-driven set to flicker together. With several flickering LEDs, each in series with several more LEDs, you can make a wide and striking effect.
    You can read more about this see an example application, here: http://www.evilmadscientist.com/2012/flicker-leds/

    As far as the AC goes, I would recommend that you build a basic AC to DC converter, such as the "Full-wave Rectifier with Smoothing Capacitor" described here: http://www.electronics-tutorials.ws/diode/diode_6.html

    This circuit can be made as simply as four diodes plus a capacitor, or with an off-the-shelf bridge rectifier (e.g., Jameco Part number 178001, $0.29) and a capacitor (say Jameco part number 93761). 6.3 V AC will give you roughly 4.5 V DC with this circuit-- enough voltage to power two LEDs in series, or one in series with a resistor.

    You could also run flickery flame kits directly from that 4.5 V DC. If your machine's output circuit was rated for 0.25 A, then you would have enough power to run three Flickery Flame kits off of that one output. (Figure ~80 mA each typical draw.)

    One note is that our white Flickery Flame kits are designed to run from 4.5 V DC, but the red/yellow Flickery Flame kits are designed to run from 3 V. So, three off-the-shelf white kits should work fine, but if you were using the red/yellow kits, you would want to substitute in a different resistor value, perhaps 150 ohms or so.

  • Thank you very much for the detailed information, this is perfect!  It makes so much more sense now!  I looked at the 150ohm resistors on Jameco, but there are 1/2 watt and 1/4 watt.  How do I know which to choose based on the above application? 

    Ultimately, I would like to run 3 kits off of one output to start with, but if I were to build something custom like the series LED link above, what would be the maximum number of LEDs I would be able to power from that 4.5V DC?

    Thanks again!
  • 4.5 V DC is enough to run _one_ LED if it is blue, white, or "pure" green.  It's enough to run two red or yellow LEDs in series.
  • I got my kits and assembled the AC/DC circuit and it works great!  I'm wondering if I can connect a 4th Flickery Flame kit or would that be too much of a draw for the conversion circuit?  Or would it just dim all of the LEDs?

  • I don't know how much available power supply capacity you have in your machine-- I suspect that it's high enough that another lightbulb worth of power (enough to run several more kits) would not be a problem. The limits that I suggested were based on just using as much power as a single light bulb.  The conversion circuit itself should be able to run 10+ Flickery Flame kits.
  • Also: Awesome project, looks great!  We have a hyperball machine, ourselves. ;)
  • I built the same circuit as pinballdude using the flicker flame kits and the bridge rectifier circuit on a prototype board. Is it possible to change out the leds on the flicker flame kit to get a "bubbling green" effect?  If so, do the resistor values need to change (I switched to 150 ohms per the above discussion)?
  • I don't know of any LEDs sold with a "bubbling" effect, but we do have yellow-green candle flicker LEDs which can be used in place of the red or yellow ones. You can see all of our bulk candle flicker LEDs here: http://shop.evilmadscientist.com/component/content/article/189