Re: [oopic] PWM freq choice (was: H-Bridge issue...maybe.)

I have a Sabertooth. We discussed that months back, but once I got it, and
began playing around with it, I found that the speed value that corresponded
to off was a fairly vague point in the middle of the range from 0-127. In
fact, the point seemed slightly different for the two motors, and even when
the tracks weren't turning, the motors were humming, which I took to mean
that plenty of current was flowing (I didn't test how much, but if there's
noise, there's power), even at the point that the motors should have been
stopped. This was while the Sabertooth was set in analog operating mode,
which I believe is the right setting for use with PWM control.

To get around this, I would need to use a relay to shut off power to the
motors when they were not in use. Since they will not be in use for maybe
half the time, I certainly don't want to be running their batteries down
during that time.

I actually need almost the same circuit with the Low-Cost H-Bridge, since I
will need to disable the motors while the battery is charging, so the
circuit isn't that big an issue. It is also possible that there is a
different setting for the Sabertooth that would work other than the analog
mode, but I haven't really gone looking very far. The Sabertooth is
primarily targeted at the RC world.

rtstofer wrote:
>
> --- In oopic@yahoogroups.com, Shaggy <charrington@...> wrote:
>>
>>
>> There are so many posts, replies, and whatnot to this thread at this
> point
>> (spread over several months, too), that I am getting lost in them.
> Frankly,
>> I'm wondering whether I even quoted the correct piece in my original
> post,
>> earlier today.
>
> So, why don't we start over with a link to the H-Bridge and motor that
> you actually have?
>
> Off hand, it seems close and you can't do anything about stall current,
> that's what the motor will draw when it first starts rotating before
> the motor starts generating back-emf.
>
> Overheating from long term running at 1A is likely but can be solved
> with a heatsink. Stall current and the 2A limit is not usually
> negotiable.
>
> Were it mine, I would opt for a much larger H-Bridge. Maybe the
> Sabertooth 5A dual motor device.
>
> Richard
>
>
>
>

--
View this message in context: http://www.nabble.com/H-Bridge-issue...maybe.-tp13928519p15797018.html
Sent from the OOPic mailing list archive at Nabble.com.

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