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55957Re: FullSpeed Dozer

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  • jing.alcantara
    Jun 2 7:24 AM
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      hi Jo,

      i just finished my mobile platform and hooked up my DOZER and guess
      what? it just sits there DOZING. i know it works cuz when i lift the
      base the motor runs so i guess i needed a motor driver. but i dont
      have the 74***245 chip, what i got is the 74ACT240. i tried googling
      for a circuit that uses this chip but my efforts turn futile. can you
      give me a schematic for a motor driver that uses the 74ACT240 chip.
      thanks again.

      jing

      --- In beam@yahoogroups.com, "Joseph Charles" <jodicalhon@...> wrote:
      >
      > Hi Jab,
      >
      > I've actually come full circle on this.
      >
      > I noticed last night that the 74AC14 full-speed dozer seemed to
      need a
      > fair difference in light levels on each of the PD's in order to
      react.
      > If it went into a less well-lit part of the room, it basically
      became
      > a bit 'visually impaired' and just chugged around, not reacting
      when I
      > shaded a PD. I had to make one PD very much darker than the other
      one
      > to get a reaction.
      >
      > I assume the largish hysteresis of the 74AC14 inputs, and the very
      > high resistance of the PD bridge, when darkish, compared to the 10M
      > oscillator resistor, may be at play here. (Could be wrong, though!)
      >
      > I swapped out the PD's for a pair of phototransistors, with current
      > limiting 1k resistors (one for each PT), and the sensitivity was
      > greatly improved.
      >
      > But I looked at the increasing parts count and thought, "Hmmm...".
      >
      > So I breadboarded the original 'waddle' bot (with reverse), and set
      it
      > loose. I've decided I actually prefer the funny little movement of
      > this version, and its sometimes unpredictable reactions, to the more
      > 'souped-up' versions.
      >
      > It think that Wilf's 74AC240 BullDozer circuit won't have the same
      > insensitivity problems that my 74AC14 version had, so it might be
      fun
      > to have a go at building that one.
      >
      > This also confirms why I like to use breadboards (and some sort of
      > test base, too). You can chop and change a circuit, and try as many
      > variations as you like, before settling on a final design.
      >
      > Jo
      >
      >
      > --- In beam@yahoogroups.com, "jabmechtech" <jabmechtech@> wrote:
      >
      > > I can't build this yet, I'm short on the part count. It seemed to
      > > keep climbing.:(
      >
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