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555 question

K

kd6532

Jan 1, 1970
0
I'm designing a circuit, wherein I'm trying to use a 555 operating in
monostable mode to turn on an array of sensors for about one second.
I've chosen by exernal R (10k) and C(100u) accordingly. My trouble is
with the triggering. My triggering will be coming from a close contact
that will be closed for a long period of time, opened for a unknown
amount of time, and closed again. I need the 555 to output the 1
second pulse when the switch closed (it's imperative). What would be
the easiest method to do this, while consuming the least amount of
current. Some kind of positive edge triggered component, RC network,
etc.? One problem is that the input triggering pulse must typically be
smaller than the output, which is a problem since the door is opened
for an unknown amount of time.

Thanks.
Kris
 
J

James Beck

Jan 1, 1970
0
I'm designing a circuit, wherein I'm trying to use a 555 operating in
monostable mode to turn on an array of sensors for about one second.
I've chosen by exernal R (10k) and C(100u) accordingly. My trouble is
with the triggering. My triggering will be coming from a close contact
that will be closed for a long period of time, opened for a unknown
amount of time, and closed again. I need the 555 to output the 1
second pulse when the switch closed (it's imperative). What would be
the easiest method to do this, while consuming the least amount of
current. Some kind of positive edge triggered component, RC network,
etc.? One problem is that the input triggering pulse must typically be
smaller than the output, which is a problem since the door is opened
for an unknown amount of time.

Thanks.
Kris
What did someone say, the PIC10 and 12 series are the 555 of today?
I would just about agree, with a little programming you could do the
above without all the external support parts. Use the internal RC osc
and you are on your way. Just look for the edge, do the output "thing"
and wait for the next edge, rising or falling, it's up to you.

Jim
 
C

Charles Schuler

Jan 1, 1970
0
kd6532 said:
I'm designing a circuit, wherein I'm trying to use a 555 operating in
monostable mode to turn on an array of sensors for about one second.
I've chosen by exernal R (10k) and C(100u) accordingly. My trouble is
with the triggering. My triggering will be coming from a close contact
that will be closed for a long period of time, opened for a unknown
amount of time, and closed again. I need the 555 to output the 1
second pulse when the switch closed (it's imperative). What would be
the easiest method to do this, while consuming the least amount of
current. Some kind of positive edge triggered component, RC network,
etc.? One problem is that the input triggering pulse must typically be
smaller than the output, which is a problem since the door is opened
for an unknown amount of time.

http://www.unitechelectronics.com/NE-555.htm

Search on this page for differentiator.
 
J

John Fields

Jan 1, 1970
0
I'm designing a circuit, wherein I'm trying to use a 555 operating in
monostable mode to turn on an array of sensors for about one second.
I've chosen by exernal R (10k) and C(100u) accordingly. My trouble is
with the triggering. My triggering will be coming from a close contact
that will be closed for a long period of time, opened for a unknown
amount of time, and closed again. I need the 555 to output the 1
second pulse when the switch closed (it's imperative). What would be
the easiest method to do this, while consuming the least amount of
current. Some kind of positive edge triggered component, RC network,
etc.? One problem is that the input triggering pulse must typically be
smaller than the output, which is a problem since the door is opened
for an unknown amount of time.

---
View in Courier:

+V>----+-----------+------+-------+--------+---------------+
| | |K | |8 |
[10K] [100K] [1N4148] [750K] +---+---+ |
| | | | 2|_ Vcc |3 |
+--[0.1µF]--+------+-------|---O|T OUT|--->OUT |
| | 6| | |
| +----|TH | |C1
| O | 7|_ 555| [0.1µF]
S1-->| +---O|D | |
| O | | GND | |
| |+ +---+---+ |
| [1µF] |1 |
| | | |
GND>---+--------------------------+--------+---------------+

C1 goes directly across pins 1 and 8
 
A

Anthony Fremont

Jan 1, 1970
0
John said:
I'm designing a circuit, wherein I'm trying to use a 555 operating in
monostable mode to turn on an array of sensors for about one second.
I've chosen by exernal R (10k) and C(100u) accordingly. My trouble is
with the triggering. My triggering will be coming from a close
contact that will be closed for a long period of time, opened for a
unknown amount of time, and closed again. I need the 555 to output
the 1 second pulse when the switch closed (it's imperative). What
would be the easiest method to do this, while consuming the least
amount of current. Some kind of positive edge triggered component,
RC network, etc.? One problem is that the input triggering pulse
must typically be smaller than the output, which is a problem since
the door is opened for an unknown amount of time.

---
View in Courier:

+V>----+-----------+------+-------+--------+---------------+
| | |K | |8 |
[10K] [100K] [1N4148] [750K] +---+---+ |
| | | | 2|_ Vcc |3 |
+--[0.1µF]--+------+-------|---O|T OUT|--->OUT |
| | 6| | |
| +----|TH | |C1
| O | 7|_ 555| [0.1µF]
S1-->| +---O|D | |
| O | | GND | |
| |+ +---+---+ |
| [1µF] |1 |
| | | |
---+--------------------------+--------+---------------+

C1 goes directly across pins 1 and 8

Need some theory help here. :) What's going on with the 10k, .1uF, 100k,
and diode? While the button is up, I'm thinking that 10K charges that side
of the cap faster (obviously), keeping the trigger high as the charging goes
on. Then when the button is pushed, that side of the cap is yanked to
ground causing the other side to do basically the same thing resulting in
triggering the 555. While the button is held down, the right side (100k
side) of the cap proceeds to charge back to +V thru the 100K resistor. When
the button is released, the left side begins charging towards the V+ rail
possibly causing the right side to attempt to rise above V+. The diode
stands in the way of that letting the extra voltage dump into the V+ rail.
Is that close?
 
A

Anthony Fremont

Jan 1, 1970
0
James said:
What did someone say, the PIC10 and 12 series are the 555 of today?
I would just about agree, with a little programming you could do the
above without all the external support parts. Use the internal RC osc
and you are on your way. Just look for the edge, do the output
"thing" and wait for the next edge, rising or falling, it's up to you.

Show us your code. :) Them's the rules. If you say "use a pic" you're
obligated to show how it's done. ;-)
 
J

John Fields

Jan 1, 1970
0
..+V>----+-----------+------+-------+--------+---------------+
.. | | |K | |8 |
.. [10K] [100K] [1N4148] [750K] +---+---+ |
.. | | | | 2|_ Vcc |3 |
.. +--[0.1µF]--+------+-------|---O|T OUT|--->OUT |
.. | | 6| | |
.. | +----|TH | |C1
.. | O | 7|_ 555| [0.1µF]
.. S1->| +---O|D | |
.. | O | | GND | |
.. | |+ +---+---+ |
.. | [1µF] |1 |
.. | | | |
..GND>---+--------------------------+--------+---------------+
 
J

John Fields

Jan 1, 1970
0
..+V>----+-----------+------+-------+--------+---------------+
.. | | |K | |8 |
.. [10K] [100K] [1N4148] [750K] +---+---+ |
.. | | | | 2|_ Vcc |3 |
.. +--[0.1µF]--+------+-------|---O|T OUT|--->OUT |
.. | | 6| | |
.. | +----|TH | |C1
.. | O | 7|_ 7555| [0.1µF]
..S1-->| +---O|D | |
.. | O | | GND | |
.. | |+ +---+---+ |
.. | [1µF] |1 |
.. | | | |
..GND>---+--------------------------+--------+---------------+
 
A

Anthony Fremont

Jan 1, 1970
0
John said:
.+V>----+-----------+------+-------+--------+---------------+
. | | |K | |8 |
. [10K] [100K] [1N4148] [750K] +---+---+ |
. | | | | 2|_ Vcc |3 |
. +--[0.1µF]--+------+-------|---O|T OUT|--->OUT |
. | | 6| | |
. | +----|TH | |C1
. | O | 7|_ 555| [0.1µF]
. S1->| +---O|D | |
. | O | | GND | |
. | |+ +---+---+ |
. | [1µF] |1 |
. | | | |
.GND>---+--------------------------+--------+---------------+
Need some theory help here. :) What's going on with the 10k,
.1uF, 100k, and diode? While the button is up, I'm thinking that
10K charges that side of the cap faster (obviously), keeping the
trigger high as the charging goes on. Then when the button is
pushed, that side of the cap is yanked to ground causing the other
side to do basically the same thing resulting in triggering the 555.
While the button is held down, the right side (100k side) of the cap
proceeds to charge back to +V thru the 100K resistor. When the
button is released, the left side begins charging towards the V+
rail possibly causing the right side to attempt to rise above V+.
The diode stands in the way of that letting the extra voltage dump
into the V+ rail. Is that close?

Clever :)
 
R

Rich Grise

Jan 1, 1970
0
Show us your code. :) Them's the rules. If you say "use a pic" you're
obligated to show how it's done. ;-)

Hear, hear!

Thanks,
Rich
 
L

Lord Garth

Jan 1, 1970
0
Anthony Fremont said:
Of course the next time you suggest a 555, you have to post a schematic as
well. ;-)


PSST! This is a non binaries group! Redirect them to A.B.S.E. or there can
be no schematic posted excepting only crappy ASCII art.
 
J

James Beck

Jan 1, 1970
0
Show us your code. :) Them's the rules. If you say "use a pic" you're
obligated to show how it's done. ;-)

How's this?

while(TRUE)
{
if(edge_hightolow() && timed_out())
handle_output();
}

or

while(TRUE)
{
if(edge_lowtohigh() && timed_out())
handle_output();
}

Now, just fill in the functions.....
;)

Jim
 
B

Bobo The Chimp

Jan 1, 1970
0
How's this?

while(TRUE)
{
if(edge_hightolow() && timed_out())
handle_output();
}
}
or

while(TRUE)
{
if(edge_lowtohigh() && timed_out())
handle_output();
}
}
Now, just fill in the functions.....
;)

Jim

Yeah, why don't I just go ahead and do that while you go outside and play
"hide and go **** yourself"?

Cheers!
Bobo
 
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