Pinball VAC event sensing in parallel

Discussion in 'The Projects Forum' started by esoT, Feb 5, 2015.

  1. esoT

    Thread Starter New Member

    Feb 4, 2015
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    0
    Hello everyone, thank you for taking the time to look at my project.

    I am attempting to sense "pinball events" which include hitting switches, contacting the pop bumpers, triggering the flippers etc on an older Electro-Mechanical pinball machine made in the 1970s by Gottlieb. I have attached an excerpt of the schematic below, which shows several of the pinball components and the way they are wired up. Labeling outside of this photograph shows that there is 25 VAC running across these components in parallel.
    pinballschematic.JPG
    I have built the circuit below, replacing the diode array with a GBL005 Bridge rectifier, the power entering the Bridge Rectifier is 25 VAC, and I have left off the fuse. I am planning to use the dedicated 5V to trigger an Arduino's I/O pin, and am using a 10k Ohm resistor in parallel before the I/O pin just like in the basic Arduino button example. With a single circuit I have been able to measure individual pinball events around the machine including the flippers, pop bumpers, switches etc.
    [​IMG]
    When I go to add a second of the above circuit arrangement, I am getting false I/O positives in that one pinball event will trigger both or all I/O pins attached to the pinball circuit. I have tried placing my circuit in parallel with the relays, with the NO switches, and in series before the switch. I figured that it was now time to call in the experts so any help / advice or even questions requesting clarification are welcome.

    Thank you
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    I am really confused about how you are detecting the presence or absence of 24Vac into an Arduino pin which should never be driven more negative than 0V or more positive than +5V?

    Post a schematic of how you are interfacing the solenoids in the machine to the Arduino?
     
  3. esoT

    Thread Starter New Member

    Feb 4, 2015
    3
    0
    Quick edit: This is the same circuit diagram as displayed above, just including the Arduino.

    pinballschematic_bb.jpg
    The bridge rectifier (demonstrated here by the diode array) transforms the 25 VAC into DC, with the capacitor smoothing out the waveform somewhat. This explanation seems to be pretty clear, but I don't need to step down the voltage since I am not starting from 120 VAC off the wall but the 25VAC that comes from the transformer in the pinball machine. The 7805 regulator takes the DC voltage coming off the bridge rectifier and turns it into a dedicated +5V, and maintains the same ground. All of the ground gets filtered back to the AC wave through the upper half of the bridge rectifier.

    photo.JPG

    I have attached the orange / white wire above in parallel across both the relay coil, and the NO switch and have gotten a single pinball event to trigger an Arduino I/O pin without issue. With more than one of these (across more than one pop bumper per se) one event triggers both I/O pins.
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Have you considered a AC input opto coupler, there are several different types out there H11AA1 IL255 etc.
    You can place a small cap across the output transistor for smoothing.
    Eliminates a few components.
    Max.
     
  5. esoT

    Thread Starter New Member

    Feb 4, 2015
    3
    0
    I've looked at the IL255 which seems to be close. As far as you know, will I be able to place a number of them in the circuit without interference between them using the same Arduino?

    I'm also worried about going beyond the max forward current as some of the pinball components require more than the 3A max listed for the IL255.
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The transistor output emitters can share the same common as the Arduino.
    The input is listed as 130ma max, so you require a series resistor that does not exceed this, aim for something at 50% at first.
    This will be in parallel with the coil or 'bumper'.
    Max.
     
  7. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    The circuit you posted will work for a single channel, but not for multiple channels...
     
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