Quadcore question

Discussion in 'Intelligence & Machines' started by domesticated om, Aug 1, 2011.

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  1. domesticated om Interplanetary homesteader Valued Senior Member

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    I'm not building a walking robot. A friend of mine with an interest in building BEAM robots introduced me to this, and ever since we've been building little test circuits to get this to work.

    At any rate ... an explanation of a 'quadcore'
    http://www.beam-wiki.org/wiki/Quadcore

    ....so my test ckt consists of four 1 k resistors, four 100uF caps, a Schmitt trigger IC, and four LEDs

    I'm not exactly sure what I'm doing wrong, but I haven't gotten this to work properly. It's supposed to oscillate between each of the four cores separately one after the other. Instead, it oscillates in pairs (two at a time).

    The wiki article I pointed to describes it working in pairs, but doesn't seem to provide information on how to make the processes run separately unless I'm missing something.



    Footnote - I could cheat and just do a single core attached to a ripple counter and a quad switch .... but I'm determined to do this exercise properly to learn something. I'm guessing BEAM is supposed to be more about biological analogies as opposed to straightforward practicality LOL.
     
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  3. leopold Valued Senior Member

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    if the chips in question have a chip enable then you can use a 4 bit serial input shift register and a 5 input nor gate. 4 of the nor gate inputs go to the outputs of the shift register, the fifth is tied to Vcc. the output of the nor is tied to both the serial inputs of the shift register. the shift register clear line is tied to Vcc. the input clock comes from the one shot.
    this will allow you to enable each chip in sequence.
    this circuit will not need a one shot because all but one chip will be disabled.
    this circuit uses active low logic.

    edit:
    the output of the nor is inverted before being applied to the serial inputs of the register.

    also, the "schematic" in the wiki article was very vague.
    the flashing yellow symbols were that of op amps not CPUs
    on the other hand op amps have 2 inputs, inverting and non inverting and CPUs have no inputs.
    and, what exactly is "the right way"?
    there are only 2 ways to go about this, software and hardware.
    very vague indeed.

    edit 2:
    in regards to a CPU having no inputs, i meant that as in inputs to something like an op amp.
    a CPU has signals sent to it ( inputs ) but without the appropriate hardware or software is totally incapable of processing them.
     
    Last edited: Aug 2, 2011
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  5. domesticated om Interplanetary homesteader Valued Senior Member

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    It's not referring to CPUs. Each "core" represents that particular end of the circuit being "discharged". It's basically a daisy chain of astable multivibrator type processes [I think]... I guess they just nickname them "cores" for this type of circuit concept.


    the robot "walks" using two DC motors. When cores one and two discharge (note - not at the same time), the DC motors spin one direction, When cores 3 and 4 discharge, the motors spin the other direction - thus making the hypothetical legs move back and forth. The motors themselves are actually irrelevant [I think] and simply happen to be attached to that portion of the the circuit when they discharge. It may as well be 4 LEDs.


    ...actually, now that I think about it, I wonder if that's it? It doesn't really matter which polarity you supply power to a DC motor -- however when you do that, it always grounds to the opposing core (example: core 1 goes to ground through core 3).
    LEDs only go one way, so I have them all going to ground on their own, and not through the opposing cores.

    Hrmmm....do you think maybe that's it?



    P.S. Yeah -- and I guess a shift register would be better than a counter in my "cheat" circuit.
     
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  7. leopold Valued Senior Member

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    do you actually need 2 motors?
    the same effect can be achieved with one motor and two gears of the same size.
    one gear is mounted on the motor shaft and the other is turned by the first gear.

    edit:
    back to the original problem i keep thinking about a bistable with Q and not Q outputs.
    the problem with this though is that the outputs will not cross zero volts.
    using this circuit we can get either of the following:
    from zero to approx. -5 volts.
    or
    from zero to approx, +5 volts.
     
    Last edited: Aug 2, 2011
  8. leopold Valued Senior Member

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  9. domesticated om Interplanetary homesteader Valued Senior Member

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    Thanks for the link


    I don't really want to move forward with creating a walking robot enough to worry about implementing this kind of algorithm. I just have all the parts (a breadboard, some caps, LEDs, and an IC) and just want to watch the circuit oscillate correctly.
     
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