Re: [oopic] H-Bridge issue...maybe.

Actually, I already know it is getting hot. There's a small heat sink on the
H-Bridge chip, and I have noted that it is mighty warm after 10s of
operation.

As for the current draw, I'll have to leave that until tomorrow.

Thanks for the help.

rtstofer wrote:
>
> --- In oopic@yahoogroups.com, Shaggy <charrington@...> wrote:
>>
>>
>> Ok, I took a look at the voltage coming from the OOPic at various speed
>> settings. The voltage dropped steadily down to below 1V on the
> analog meter
>> at a value around 70.
>
> So, presumably, the OOPic is producing a variable width pulse. That's
> good...
>
>>
>> However, I also went looking at the motor specs. The no load draw is
> 300 mA,
>> but the max draw at shaft lockup is 2A. I would have thought there
> was less
>> current draw at lower voltage, but I may be getting that wrong. In any
>> event, the 1A limit is being doubled.
>
> Sure, there will be lower current at lower voltage but it may not be
> enough to rotate the motor. At some point the voltage/current is
> sufficient to spin the motor and at that point the current may be too
> much for the driver.
>
> If your meter will measure current of a suitable range, connect it in
> series with one of the motor leads and see what you get. If it tries
> to exceed 1A, the driver chip should shut down. If you have a second
> meter, you might try to measure the voltage at the same time.
>
> The thing is, if the chip shuts down, I expect it to stop after a
> short delay while it heats up. It is a thermal shutdown, not an
> actual overcurrent shutdown. Or, at least that's what the datasheet
> implies.
>
> Remove the oDCMotor2 object and set the IOLines directly. When IOLine
> 17 (or 18) is set to '1' and the other two lines are in opposite
> states, the motor should run full speed.
>
> Touch the chip while the motor is running and see if it is getting hot.
>
> Richard
>
>
>
>

--
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