at EVERY other value?
The thing that has me really baffled about this is why I am not seeing any
kind of linnear degradation of operation. While the problem could be could
be power draw, or it could be pulse frequency, I don't have any workable
explanation why I get a steadily ramping up of activity up to 126, then
suddenly full speed ahead at 127. The lack of activity below 127 (the
ramping up is nothing to chirping to vibrating the tracks, they never
actually turn) all looks like it could be caused by a variety of issues, but
why do those issues go away at 127? What is different about that setting as
compared to the others. Looking at the voltage on the lines doesn't show
anything different at 126 vs 127, which is understandable since a smooth
curve would make those two nearly identical.
Does a setting of 127 on the oDCMotor2 behave in a different fashion than
all other settings? Is full speed ahead special in some way as far as pulse
frequency, or current?
rtstofer wrote:
>
> The oDCMotor2 uses the oPWMH to create the pulses and the oPWMH object
> defaults to 19.6 kHz. This is because the PWM.period is set to 254 or
> (20 MHz / 4 / 254 = 19,685) and the .prescale is set to 0.
>
> Unless you look specifically at the old oPWM object, the new
> documentation doesn't tell you that you can control the prescale and
> period properties.
>
> PreScale = 0 -> 5 MHz base frequency
> PreScale = 1 -> 5 MHz / 4 base frequency
> PreScale = 2 -> 5 MHz / 16 base frequency
>
> Period = 1..255 -> PWM frequency = base frequency / period
>
> This works with V6:
>
> Dim m as oPWM 'NOT oPWMH
>
> sub main()
>
> m.PreScale = 2 ' divide by 16
> m.Period = 255 ' divide by 255 (256?)
> m.DutyCycle = 127 ' 50% duty cycle
> m.IOLine = 18 ' or IOLine = 17
> m.Operate = 1 ' fire it up
>
> end sub
>
> End result is a 50% duty cycle at about 1 kHz.
> Does the H-Bridge still work with the original motor?
>
> Post a link to the new H-Bridge so we can look at it before you buy.
>
> I think you will be better off to dump the oDCMotor2 object (and/or
> the oPWMH object) and just use the oPWM object. This will allow you
> to get a low frequency and the driver may work better. Of course,
> you will have to control the two signal lines separately to get
> forward/reverse/brake. Unfortunately, it will be audible as the motor
> runs at very low speed.
>
> I don't know why the .prescale and .period properties were dropped
> from oDCMotor2 and oPWMH but it can certainly cause a problem.
>
> Richard
>
>
>
>
> --- In oopic@yahoogroups.com, Shaggy <charrington@...> wrote:
>>
>>
>> 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.
>
>
>
>
--
View this message in context: http://www.nabble.com/H-Bridge-issue...maybe.-tf4867316.html#a13959536
Sent from the OOPic mailing list archive at Nabble.com.
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