Want independant pulse width variation on + and - side of gn

[jtaylor]

Subject says most of it; power requirements are small, frequency and some
pulse width drift/variation is no problem...

 

[Tim Wescott]

jtaylor wrote:

Subject says most of it; power requirements are small, frequency and some
pulse width drift/variation is no problem...

555 + diode + two pots + some thought.

First line says most of it; power requirements will be small, frequency
and pulse width drift won't be too bad.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[jtaylor]

Tim Wescott <tim@wescottnospamdesign.com> wrote in message
news:10mt5qda8rtbp7d@corp.supernews.com...

jtaylor wrote:

Subject says most of it; power requirements are small, frequency and
some
pulse width drift/variation is no problem...


555 + diode + two pots + some thought.

First line says most of it; power requirements will be small, frequency
and pulse width drift won't be too bad.

Are you sure about this?

In more obvious terms, I want to be able to vary the + width from 0 to 100%
independently from the - width (which should also be variable from 0 to 100%
independently from the + width).

 

[John Popelish]

jtaylor wrote:

Tim Wescott <tim@wescottnospamdesign.com> wrote in message
news:10mt5qda8rtbp7d@corp.supernews.com...
jtaylor wrote:

Subject says most of it; power requirements are small, frequency and
some
pulse width drift/variation is no problem...


555 + diode + two pots + some thought.

First line says most of it; power requirements will be small, frequency
and pulse width drift won't be too bad.

Are you sure about this?

In more obvious terms, I want to be able to vary the + width from 0 to 100%
independently from the - width (which should also be variable from 0 to 100%
independently from the + width).

How can the positive and negative parts both be 100% (duty cycle?) at
the same time or 0% at the same time (infinite frequency)?

Or are you saying that you want the on time to be variable from some
small time to some maximum time and also the off time to be variable
from some small time to some maximum time and variations in the
duration of one state does not affect the duration of the other state?

--
John Popelish

 

[jtaylor]

John Popelish <jpopelish@rica.net> wrote in message
news:416EA3A9.6BA8F9E2@rica.net...

How can the positive and negative parts both be 100% (duty cycle?) at
the same time or 0% at the same time (infinite frequency)?

Or are you saying that you want the on time to be variable from some
small time to some maximum time and also the off time to be variable
from some small time to some maximum time and variations in the
duration of one state does not affect the duration of the other state?

Um, no. I want ground in the middle, and the other line to go from say +5v
to -5v, at about 1kHz, with the + pulse varying in width, and the - pulse
varying in width.

 

[jtaylor]

Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote in message
news:7jetm01ar7l285qog0fso67k4okgc1fbqc@4ax.com...

On Thu, 14 Oct 2004 14:28:22 -0300, the renowned "jtaylor"
jtaylor@hfx.deletethis.andara.com> wrote:


John Popelish <jpopelish@rica.net> wrote in message
news:416EA3A9.6BA8F9E2@rica.net...

How can the positive and negative parts both be 100% (duty cycle?) at
the same time or 0% at the same time (infinite frequency)?

Or are you saying that you want the on time to be variable from some
small time to some maximum time and also the off time to be variable
from some small time to some maximum time and variations in the
duration of one state does not affect the duration of the other state?


Um, no. I want ground in the middle, and the other line to go from say
+5v
to -5v, at about 1kHz, with the + pulse varying in width, and the - pulse
varying in width.

You can consider connecting the "GROUND" pin on the 555 to -5V. It'll
never know the difference, you know.

Yes, but how would I get a (say) drop from ground to -5V lasting for
1/4000th second , returning to 0V for 1/4000th second (1/2 cycle of 1kHz at
50%) followed by (say) a rise from 0V to +5V lasting for 1/8000th second,
returning to 0V for 3/8000ths of a scond (1/2 cycle of 1Khz at 25%)?

 

[Rich Grise]

On Thu, 14 Oct 2004 14:58:13 -0400, Spehro Pefhany wrote:

On Thu, 14 Oct 2004 15:06:03 -0300, the renowned "jtaylor"
jtaylor@hfx.deletethis.andara.com> wrote:


Yes, but how would I get a (say) drop from ground to -5V lasting for
1/4000th second , returning to 0V for 1/4000th second (1/2 cycle of 1kHz at
50%) followed by (say) a rise from 0V to +5V lasting for 1/8000th second,
returning to 0V for 3/8000ths of a scond (1/2 cycle of 1Khz at 25%)?

Okay. If you use a single 555 in astable mode you can steer the
currents through both ends of your two pots to get this effect by
using a FF (eg. 1/2 4013) and 2 complimentary pairs of transistors.

Driving the output to the 3 levels depends on how much drive you need.
One possibility would be to use 1/2 of a 4052. It could also be done
with discretes.

I'd have done it with discretes. Eight of them, to be exact. (maybe ten,
if you don't want Rb to go to zero. ;-) )

Cheers!
Rich