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Thread: Circuit Design Help Needed

  1. #11
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    What exactly is it you are trying to get the circuit to do. As with all electronic circuits, there is always more than one way to achieve the same result.

    My go to CMOS chips are the 4093 and the 4066. These two chips can be manipulated to do most tasks. Sure there are others but there isn't much you can't make using these two.

  2. #12
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    Quote Originally Posted by Autosteve View Post
    What exactly is it you are trying to get the circuit to do. As with all electronic circuits, there is always more than one way to achieve the same result.

    My go to CMOS chips are the 4093 and the 4066. These two chips can be manipulated to do most tasks. Sure there are others but there isn't much you can't make using these two.
    I have three DPDT illuminated (incandescent) momentary switches.
    The lamp it lit by putting 12v across the two common pins.
    I need the lamp on switch A to come on when it is pressed, then go out when either switch B or C is pressed and whichever switch (B or C) is pressed then it's light needs to come on and stay lit until either of the other two switches are pressed.
    In addition to that function I need the three switches to control three button inputs on a J-Pac at the same time.

    The three switches are for the weapons select in the Starfighter game and the lamps should indicate which weapon is currently selected/active.

    Last edited by Kaizen; 27th April 2019 at 09:43 PM.
    Namco Starblade - Taito Cocktail 14" x 3, 20" x 2 - NZ SI PtII Upright - Chase HQ DX, Taito Top Speed - Taito Grand Champion - Taito Safari - LAI SI Head to Head Cocktail - SI Cocktail Clone x 2, Pong Clone x 3

  3. #13
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    Your circuit looks a little convoluted, but the obvious issue I can see is the 10K pullups to +12V for the switches will be feeding into the J-Pac. Putting a diode in series with the 3 lines going to the J-Pac (anode towards the J-Pac) will stop that.

    The other issue is you don't seem to have the required 100n (0.1uF) decoupling capacitor across the power for each IC. Leaving these out can lead to wildly unstable operation and possible damage.
    "Everyone's always in favour of saving Hitler's brain. But when you put it in the body of a great white shark, ooohh! Suddenly you've gone too far!"

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    Quote Originally Posted by David_AVD View Post
    Your circuit looks a little convoluted, but the obvious issue I can see is the 10K pullups to +12V for the switches will be feeding into the J-Pac. Putting a diode in series with the 3 lines going to the J-Pac (anode towards the J-Pac) will stop that.

    The other issue is you don't seem to have the required 100n (0.1uF) decoupling capacitor across the power for each IC. Leaving these out can lead to wildly unstable operation and possible damage.
    Cheers @David_AVD, I'm going to build another PCB and will add them in across all IC's.
    When I designed the schematic there was nothing online that I could find to do the job and and I had no experience in circuit design so I followed a few suggestions, added this and tweaked that to get it working without the J-Pac connected.
    I have a handful of 12v mini relays on hand and was thinking I could use a pair on each switch to isolate the J-Pac and PCB inputs.
    Namco Starblade - Taito Cocktail 14" x 3, 20" x 2 - NZ SI PtII Upright - Chase HQ DX, Taito Top Speed - Taito Grand Champion - Taito Safari - LAI SI Head to Head Cocktail - SI Cocktail Clone x 2, Pong Clone x 3

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    So here's my solution, it may be cumbersome but as long as it works.



    PDF link for clearer viewing...

    https://drive.google.com/open?id=1Vh...iBYhcIRbRCNv5D
    Namco Starblade - Taito Cocktail 14" x 3, 20" x 2 - NZ SI PtII Upright - Chase HQ DX, Taito Top Speed - Taito Grand Champion - Taito Safari - LAI SI Head to Head Cocktail - SI Cocktail Clone x 2, Pong Clone x 3

  6. #16
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    I just had a better look at the circuit, looks fine
    Last edited by thegrunta666; 27th April 2019 at 01:42 PM.

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    Only issue was the ground for the output relays needed to come from the ground on the J-Pac.

    https://drive.google.com/open?id=1rw...k-4h3gwuxYpFK8

    I redrew the schematic and laid it out on Vero Board.
    It still needs to be double checked for errors.



    Then I got to thinking it would be a waste of time building a new PCB if it didn't work correctly so I just made up a relay board and wired it into the PCB & J-Pac.
    The relay pins in the DIY Layout Creator library don't match up with the relays I was using in case anyone is wondering why some of the pins aren't connected.



    Tested and everything works fine, I may make up the new PCB or just be lazy and keep the relay board separate.



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    I don't think Centauri will be knocking on my door any time soon.




    Thanks to all who commented for your input.
    Namco Starblade - Taito Cocktail 14" x 3, 20" x 2 - NZ SI PtII Upright - Chase HQ DX, Taito Top Speed - Taito Grand Champion - Taito Safari - LAI SI Head to Head Cocktail - SI Cocktail Clone x 2, Pong Clone x 3

  8. #18
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    Cool, glad you got it working. I think it is possible to use no relays and have the outputs of the flip flops driving the inputs of something like a ULN2003 as seen here...

    https://www.google.com.au/search?q=u...w=1140&bih=718

    The advantage using these ULN series of chips is you have no relay coil spikes to quench using diodes, you have no driver transistor circuitry needed to drive the coils but each of the chip's outputs can drive lamps, LEDs etc direct.

    These parts are designed to work directly off other IC outputs so very low current draw.

    Basically, it cuts the parts required to a minimum as well as speeding the circuit up as relays are regarded as slow in operation not that that is a major consideration in your circuit.

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    Thanks for that, I can see it would be a simpler option for the lamps.
    The active flip flop output is on constantly but the J-Pac input should be momentary, I guess you could use the output from the first three hex inverters that set the flip flops for the J-Pac but it still needs to be isolated from the J-Pac (use optos??).
    Namco Starblade - Taito Cocktail 14" x 3, 20" x 2 - NZ SI PtII Upright - Chase HQ DX, Taito Top Speed - Taito Grand Champion - Taito Safari - LAI SI Head to Head Cocktail - SI Cocktail Clone x 2, Pong Clone x 3

  10. #20
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    Quote Originally Posted by Kaizen View Post
    The active flip flop output is on constantly but the J-Pac input should be momentary,
    To make a momentary signal from a flip flop output you could add a "one shot"

    One of the 4 gates in the 4093b chip can do this for you. Just make sure you tie the unused inputs on the chip either high or low even though you don't use them.

    If you look at this page here you will see a negative edge and a positive edge triggered one shot circuit....

    https://www.electroschematics.com/wp...m=auto,-31,715

    The middle circuit will both provide a single high output pulse or the bottom circuit, a low output pulse even though the input signal is held on the Vin input. That will give you the required "momentary" signal. The capacitor sets how long the output pulse is.
    You could use this output signal to drive one of the circuits in the ULN chip and that signal provide a momentary signal to the J-Pac or use the output of the "one shot' to drive an opto direct.

    Quote Originally Posted by Kaizen View Post
    I guess you could use the output from the first three hex inverters that set the flip flops for the J-Pac but it still needs to be isolated from the J-Pac (use optos??).
    An opto will provide a clean, isolated switch closure for the J-Pac.


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