Re: Simple comparator with delay?
- From: John Fields <jfields@xxxxxxxxxxxxxxxxxxxxx>
- Date: Sun, 15 Jul 2007 15:16:20 -0500
On Fri, 13 Jul 2007 21:25:54 -0000, MRW <mr.whatever@xxxxxxxxx>
wrote:
Hi all!
I have this:
http://bayimg.com/fADbOAABN
The image shows the input and output voltages given certain
conditions. I'd like the output to equal Vsupply+ when the input
voltage passes the voltage reference. But I'd also like the output to
have delay so that it does not go to Vsupply- until a x seconds after
the input voltage drops below the reference voltage.
Will the circuit that I included work?
---
No.
---
I figured if I charge the
capacitor at the input then depending on the parallel resistor then
its discharge will take sometime.
---
The source will discharge it in as long as it took to charge it.
Try this: (View in Courier)
+5V>---------+------+--------+
| | |
VIN>---+ [R1] | [4K7]
| | | |
[POT]<--------|-\ |
| | | >------+
| +--+--|+/ LM393 |
| | | | |
| [R2] +---|--[1M]--+-----+------A
| | | | | NAND Y--+-->OUT
GND>---+-----+------+ +-+-+ +-+-+ +-B |
| | | | | |
A B A B | |
| |
Y Y | A--+
| | +-Y NAND
+-----+ B--+
| |
[1N4148] |
|K |
+-----+------------+
| |+
[Rt] [Ct]
| |
GND GND
You haven't mentioned anything about what your input signal looks
like or what OFF delay you want, so I couldn't put in many values.
Also, the pot might be able to be eliminated or replaced with a
couple of resistors.
All of the gates are parts of a quad 2-input NAND with inputs 'A'
and 'B' and outputs 'Y'
--
JF
.
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