55957Re: FullSpeed Dozer
- Jun 2, 2007hi 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.
--- In firstname.lastname@example.org, "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
> fair difference in light levels on each of the PD's in order to
> If it went into a less well-lit part of the room, it basically
> a bit 'visually impaired' and just chugged around, not reacting
> shaded a PD. I had to make one PD very much darker than the other
> 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
> 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
> 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.
> --- In email@example.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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