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Sci.Electronics.Basics -> emitter followers / Darlington - need help
There are 24 messages in this thread.
You are currently looking at messages 20 to 24.
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Author: EeyoreDate: 22:35 14-12-06
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mrdarrett@gmail.com wrote:
> Jonathan Kirwan wrote:
> > On Thu, 14 Dec 2006 21:47:32 GMT, I wrote:
> >
> > >I didn't look at the IRF530 capacitance;
> >
> > Okay. I looked. 1 nanofarad territory. That means on-times in the
> > small 10s of microseconds, roughly. If you aren't toggling around
> > faster than 1000 Hz or so, you are probably okay.
> >
> > Jon
>
> Oh. Uh... thanks. I'm running at 100 Hz.
PWM @ 100Hz is likely to be *very* noisy and the motor probably won't like it
much either.
Graham
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Eeyore wrote:
> mrdarrett@gmail.com wrote:
>
> > Jonathan Kirwan wrote:
> > > On Thu, 14 Dec 2006 21:47:32 GMT, I wrote:
> > >
> > > >I didn't look at the IRF530 capacitance;
> > >
> > > Okay. I looked. 1 nanofarad territory. That means on-times in the
> > > small 10s of microseconds, roughly. If you aren't toggling around
> > > faster than 1000 Hz or so, you are probably okay.
> > >
> > > Jon
> >
> > Oh. Uh... thanks. I'm running at 100 Hz.
>
> PWM @ 100Hz is likely to be *very* noisy and the motor probably won't like it
> much either.
>
> Graham
So, recommend 500 Hz? 1 kHz?
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Author: jasenDate: 02:20 17-12-06
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On 2006-12-15, Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
>
>
> mrdarrett@gmail.com wrote:
>
>> Jonathan Kirwan wrote:
>> > On Thu, 14 Dec 2006 21:47:32 GMT, I wrote:
>> >
>> > >I didn't look at the IRF530 capacitance;
>> >
>> > Okay. I looked. 1 nanofarad territory. That means on-times in the
>> > small 10s of microseconds, roughly. If you aren't toggling around
>> > faster than 1000 Hz or so, you are probably okay.
>> >
>> > Jon
>>
>> Oh. Uh... thanks. I'm running at 100 Hz.
>
> PWM @ 100Hz is likely to be *very* noisy and the motor probably won't like it
> much either.
something similar (phase chopping at 100Hz) is used to control hand-held AC
power tools so it can't be too bad.
OTOH going to a higher frequency is unlikely to be a bad thing.
Bye.
Jasen
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Author: Rich GriseDate: 20:48 18-12-06
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On Thu, 14 Dec 2006 23:38:05 -0800, mrdarrett wrote:
> Eeyore wrote:
>> mrdarrett@gmail.com wrote:
>> > Jonathan Kirwan wrote:
>> > > On Thu, 14 Dec 2006 21:47:32 GMT, I wrote:
>> > >
>> > > >I didn't look at the IRF530 capacitance;
>> > >
>> > > Okay. I looked. 1 nanofarad territory. That means on-times in the
>> > > small 10s of microseconds, roughly. If you aren't toggling around
>> > > faster than 1000 Hz or so, you are probably okay.
>> >
>> > Oh. Uh... thanks. I'm running at 100 Hz.
>>
>> PWM @ 100Hz is likely to be *very* noisy and the motor probably won't like it
>> much either.
>
> So, recommend 500 Hz? 1 kHz?
I once used about 100 Hz for a 12V, 1.5A motor, on a 24-36V supply,
current regulated by the switch, and it worked fine, and virtually
noiselessly. The guy who I was doing this for said that the guy who
had done the original, which I was ripping off, whined under torque.
Mine didn't complain at all. :-)
Admittedly, I had used a TIP36C and a nice heat sink. :-)
Cheers!
Rich
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