>
If he doesn't know, then he's probably using the default PWM
frequency of the oDCMotor2 object.
The oopic manual doesn't seem to give the default values, and the
sample shown doesn't specifically set them.
>
> Off the top of my head, I don't know. However, I would expect that
would not
> be an issue since the LCHB is sold by RogueRobotics to go with
their OOPic
> board. I would not expect them to be including the LCHB if it won't
work
> with the board they are using. I believe it was working as expected
when I
> had it attached to the ATS motors, which are smaller than the
Robotics
> Connection motors I am currently using.
>
> I'm leaning towards too much power draw. I'll try to look at that
this
> evening. The motors can certainly draw too much power for the LCHB,
so it is
> looking like I will have to replace that, regardless of whether
that is my
> specific problem. After all, the 754410 is getting a bit warm, even
with a
> heat sink, when I run the motors for 10s.
>
> Therefore, if anybody has a recommendation, I'll take a look at it.
> Otherwise I might just go with the H-Bridge sold by the same
company that
> sold me the chassis and motors. I'm pretty sure that one will take
enough
> power, though I will still have to look it over some.
>
>
> ooPIC Tech Support wrote:
> >
> > What is the frequency of your PWM? The 754410 is happiest at
2KHz or
> > lower. At 20KHz I've detonated these chips!
> >
> > DLC
> >
> > ooPIC Tech Support
> >
> > -----Original Message-----
> >
> > From: Shaggy <charrington@...>
> > Subj: Re: [oopic] H-Bridge issue...maybe.
> > Date: Sun Nov 25, 2007 12:38 pm
> > Size: 4K
> > To: oopic@yahoogroups.com
> >
> >
> > That's good to hear. Just having something hooked up wrong is a
much
> > better
> > problem than faulty hardware. Now how to go about figuring out
what it is.
> >
> > I have gone back to the manual for the Rogue Robotics ATS, and
confirmed
> > that my code is exactly the code they have: IOLineP is 17 for
one, and 18
> > for the other. IOLine1 is 26 and 24 respectively, and IOLine2 is
27 and 25
> > respectively. There really isn't any more code other than that
for setting
> > up the oDCMotor2. To run the motors, there is a countdown timer
which is
> > set
> > to a value in seconds. As long as it is greater than 0, the
operate
> > property
> > for each motor is set to true. When the countdown reaches 0, the
operate
> > property for each motor is set to false. That's the extent of the
code,
> > though it is not all in one place.
> >
> > As far as hooking things up, I've also reviewed that. There is a
ribbon
> > cable running from the OOPic to the Low-Cost H-Bridge (LCHB).
This ribbon
> > cable is designed so that there is only one way it can be plugged
in on
> > each
> > end, and the ends are plugged in as required. If the cable is
> > wrong....well,
> > I haven't looked at that.
> >
> > There are two pads for external power, which are labeled + and -.
I
> > soldered
> > the red lead from the battery to + and the black to -. Simple
enough. The
> > documentation then states that if external power is supplied, the
jumper
> > should be moved closer to a named capacitor. I have confirmed
that that is
> > set correctly.
> >
> > The only other connection I have made is between the motors and
the LCHB.
> > The documentation mentions color coded wires, which I can't
actually do,
> > since these motors have different colors, but I followed the
intention
> > after
> > figuring out what the colors actually meant on the ATS motors.
> >
> > If this is a ground issue, where does it lie? The LCHB is
designed to be
> > hooked up a certain way, and it is. If the connections that are
actually
> > needed are not the ones in the documentation, it's going to be a
pain to
> > figure out what's wrong.
> >
> > A couple things I'd have to look at are these:
> >
> > 1) Do the connections on the ribbon cable actually lead to where
they
> > should
> > lead? I think I don't necessarily need to test this, because it
was
> > working
> > (I think) with the ATS. I'm pretty sure I tried it with lower
speeds,
> > though
> > I was not using external power.
> >
> > 2) What does the jumper actually do? The documentation states
where the
> > jumper should be, without explaining anything about what it does.
Should
> > be
> > simple enough to trace, though not so easy to get to the board
anymore.
> >
> > Is there anything else I should be checking out?
> >
> >
> >
> > rtstofer wrote:
> >>
> >> --- In oopic@yahoogroups.com, Shaggy <charrington@> wrote:
> >>>
> >>>
> >>> Ok, this morning I set up the bot so that I could measure the
> >> voltage to the
> >>> motors. When I set the motor speed at 127, the voltage across
the
> >> motor pins
> >>> was 8.7, which is pretty reasonable. When I changed the motor
speed
> >> to 120,
> >>> the voltage across the pins was just below 1. It held steady
around
> >> 0.6V.
> >>> That's certainly a bit low for those motors.
> >>>
> >>> The second time I tested this, I got the same voltage at 127,
the
> >> same at
> >>> 120, about 0.4V at 100, then I tried 126. The voltage first
showed
> >> about 2V,
> >>> at which the wheels bumped forward some, but the voltage
dropped rapidly
> >>> down to 0.8V.
> >>>
> >>> That's not a very smooth curve. Can you point me towards a
solution?
> >>>
> >>
> >>
> >> What did you get at the OOPic pin?
> >>
> >> This sounds like the kind of thing that happens when the motor
power
> >> supply ground wire is not connected to the logic ground.
> >>
> >> As discussed in another thread a couple of days ago, you need to
> >> create a STAR ground at the motor controller chip. The logic
ground
> >> and the motor ground tie individually to that point. The
objective is
> >> to keep motor ground current off of the logic ground wire.
> >>
> >> There is a wiring diagram for the L293D (a predecessor to the
754410)
> >> at the bottom of the oDCMotor2 object reference.
> >>
> >> Richard
> >>
> >>
> >>
> >>
> >>
> >>
> >
> > --
> > View this message in context:
> > http://www.nabble.com/H-Bridge-issue...maybe.-
tf4867316.html#a13939029
> > Sent from the OOPic mailing list archive at Nabble.com.
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
>
> --
> View this message in context: http://www.nabble.com/H-Bridge-
issue...maybe.-tf4867316.html#a13957668
> Sent from the OOPic mailing list archive at Nabble.com.
>
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