example that came with the board. I also don't remember seeing anything
about the frequency, but I wasn't looking, either.
dan michaels wrote:
>
> --- In oopic@yahoogroups.com, Shaggy <charrington@...> wrote:
>>
>
>
> 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.
>>
>
>
>
>
--
View this message in context: http://www.nabble.com/H-Bridge-issue...maybe.-tf4867316.html#a13958907
Sent from the OOPic mailing list archive at Nabble.com.
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