Re: Want independant pulse width variation on + and - side of gnd;square wave of about 1kHz
From: John Fields (jfields_at_austininstruments.com)
Date: 10/16/04
- Next message: John Larkin: "Re: Electronic abbreviations."
- Previous message: John Larkin: "Re: If Kerry is elected..."
- In reply to: jtaylor: "Re: Want independant pulse width variation on + and - side of gnd;square wave of about 1kHz"
- Next in thread: Andrew Holme: "Re: Want independant pulse width variation on + and - side of gnd; square wave of about 1kHz"
- Messages sorted by: [ date ] [ thread ]
Date: Sat, 16 Oct 2004 14:21:31 -0500
On Thu, 14 Oct 2004 15:06:03 -0300, "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%)?
---
Here's a 1000 cycle square wave:
|<------500µs------>|<------500µs------>|
___ ___________________
|___________________| |_____
Then, plugging in your curious timing units, we get:
|<-----1/2000s----->|<-----1/2000s----->|
___ ___________________
|___________________| |_____
|----|----|----|----|----|----|----|----|
-->| |<---1/8000s
And, finally, if what you're asking for, above, is this:
___ ___________________
SQIN |___________________| |_____
____
+5 ___ _________| |______________
OUT |_________| |_____
-5
TIME |----|----|----|----|----|----|----|----|
-->| |<---1/8000s
This will get it for you:
+5V
|
+----+-----+--------------+
| | | |
+5V | | +--+--+ |
| +->[RV1] | | VDD | |
+--+--+ | | | |4538A| |
| Vcc | +----+-------|RC | |
|7555 | | | | | |
| OUT|---+----+-------|-------|IN | |
| | | | | | |__ _| E
| | [R1] | [C2] +-O|IN Q|---[1K]---B 2N4403
| __| | | | | | C
| TR|---+ | | | | |
| | | | | +-----+ [100R]
| TH|---+ | -5V |
| GND | | | |
+--+--+ [C1] | +--------+-->OUT
| | | | |
-5V -5V | +5V | [1000R]
| | +-----+ [100R] |
| +->[RV2] | | | GND(0V)
| | | |4538B| C
| +----+-------|RC Q|---[1K]---B 2N4401
| | | | E
| [C3] +--|IN | |
| | | |__ | |
+--------------O|IN | |
| | | | |
| | | VEE | |
| | +--+--+ |
| | | |
+----+-----+--------------+
|
-5
Select R1 and C1 to give you a 1000Hz output from the 7555.
Select RV1C2 and RV2C3 to give you a maximum pulse output width from
either 4538A or 4538B of 500µs. If you go over 500µs for either one,
or the output frequency from the 7555 is >1000Hz or the output of
either half-period from the 7555 is <500µs, The output totem-pole
will short, you'll get pretty close to zero volts out of the output,
and the only thing limiting the current through the transistors will
be the two 100 ohm resistors. With 10V across the transistors, if
they're saturated the resistors will limit the current through them to
about 50mA, which is no big deal but, if you need/want to change the
resitor values in order to get more current into your load, you'll
want to be careful not to fry the two output transistors with an
inadvertent input drive overlap.
The way it's set up now, with only the 1000 ohm resistor for a load,
the outout voltage will go from a high of +4.5V with 2N4403 on and the
2N4401 off, to ~0V with them both off, (or on!) to a low of -4.5V
with the 2N4403 off and the 2N4401 on.
--
John Fields
- Next message: John Larkin: "Re: Electronic abbreviations."
- Previous message: John Larkin: "Re: If Kerry is elected..."
- In reply to: jtaylor: "Re: Want independant pulse width variation on + and - side of gnd;square wave of about 1kHz"
- Next in thread: Andrew Holme: "Re: Want independant pulse width variation on + and - side of gnd; square wave of about 1kHz"
- Messages sorted by: [ date ] [ thread ]
Relevant Pages
|
