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You'll need to provide a bit more information. What is being switched?I require a circuit that switches off.
It is similar to the pocket calculator that will automatically switch
off if not used in a few minutes.
Could anybody please provide.
A monostable is what you need. Press the switch and it will stay on for XI require a circuit that switches off.
It is similar to the pocket calculator that will automatically switch
off if not used in a few minutes.
Could anybody please provide.
How would one design that in such a way that there would be zeroA monostable is what you need. Press the switch and it will stay on for X
minutes.
A CMOS monostable itself draws negligible current. Use its output to drive aEeyore wrote:
A monostable is what you need. Press the switch and it will stay on for X
minutes.
How would one design that in such a way that there would be zero
(or practically zero) battery draw after it shuts itself off?
Power the "power up" circuit from the switched line, and from the 'on'On Thu, 29 May 2008 17:38:01 +0100 in sci.electronics.basics, Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote,
A monostable is what you need. Press the switch and it will stay on for X
minutes.
How would one design that in such a way that there would be zero
(or practically zero) battery draw after it shuts itself off?
That makes little reals sense to my mind but is perfectly technicallyA led is to be switched off.
A simple circuit is used to switch the led on/off with 9 v.
After the led is first switched on, the switch remains activated/
closed.
However, the led should turn off after a fixed time (even though the
switch remains activated/closed), without being turned on again.
On Thu, 29 May 2008 05:22:07 -0700 (PDT), steve <kvst...@gmail.com
wrote:
I require a circuit that switches off.
It is similar to the pocket calculator that will automatically switch
off if not used in a few minutes.
Could anybody please provide.
You'll need to provide a bit more information. What is being switched?
What's available to sense the "being used" state? What control
signals, if any, are available to control power? Is any warning of
impending power termination required/desired?
The more information you can provide up front, the more targeted the
solutions can be. As it is, there's really no answer to your question.
--
Rich Webb Norfolk, VA
Gotcha. Take a look at Don's explanations of using a 555 timer chip asA led is to be switched off.
A simple circuit is used to switch the led on/off with 9 v.
After the led is first switched on, the switch remains activated/
closed.
However, the led should turn off after a fixed time (even though the
switch remains activated/closed), without being turned on again.
steve wrote:
A led is to be switched off.
A simple circuit is used to switch the led on/off with 9 v.
After the led is first switched on, the switch remains activated/
closed.
However, the led should turn off after a fixed time (even though the
switch remains activated/closed), without being turned on again.
That makes little reals sense to my mind but is perfectly technically
acheievable.
Why not use a momentary switch ?
Graham
You never heard of a ONE_SHOT ?
---A led is to be switched off.
A simple circuit is used to switch the led on/off with 9 v.
After the led is first switched on, the switch remains activated/
closed.
However, the led should turn off after a fixed time (even though the
switch remains activated/closed), without being turned on again.
---On Sat, 31 May 2008 01:46:16 -0700 (PDT), steve <kvsteve@gmail.com
wrote:
A led is to be switched off.
A simple circuit is used to switch the led on/off with 9 v.
After the led is first switched on, the switch remains activated/
closed.
However, the led should turn off after a fixed time (even though the
switch remains activated/closed), without being turned on again.
---
If you're not going to use the switch for anything else,
View in Courier:
Vcc>-+---------+-----+----------+--------+
| | | 8| |
[10K] [10K] [Rt] +---+---+ [100K]
| | | 2|_ Vcc _|4 |
+-[100nF]-+-----|-----O|T R|O---+
| | 6| | | Vout
| +------|TH 555| [100nF] /
| | 7|_ |3 | /
| O S1 +-----O|D OUT|----|--+-[Rled]--+
| O +| | GND | | |
| [Ct] +---+---+ | [LED]
| | 1| | |
GND>-+---------------+----------+--------+------------+
T = 1.1 RtCt
Vout - Vf(led)
Rled = ---------------
Iled
JF
---On Sat, 31 May 2008 18:55:34 -0500, John Fields
jfields@austininstruments.com> wrote:
On Sat, 31 May 2008 01:46:16 -0700 (PDT), steve <kvsteve@gmail.com
wrote:
A led is to be switched off.
A simple circuit is used to switch the led on/off with 9 v.
After the led is first switched on, the switch remains activated/
closed.
However, the led should turn off after a fixed time (even though the
switch remains activated/closed), without being turned on again.
---
If you're not going to use the switch for anything else,
View in Courier:
Vcc>-+---------+-----+----------+--------+
| | | 8| |
[10K] [10K] [Rt] +---+---+ [100K]
| | | 2|_ Vcc _|4 |
+-[100nF]-+-----|-----O|T R|O---+
| | 6| | | Vout
| +------|TH 555| [100nF] /
| | 7|_ |3 | /
| O S1 +-----O|D OUT|----|--+-[Rled]--+
| O +| | GND | | |
| [Ct] +---+---+ | [LED]
| | 1| | |
GND>-+---------------+----------+--------+------------+
T = 1.1 RtCt
Vout - Vf(led)
Rled = ---------------
Iled
JF
---
Oops...
Since the switch will bounce on break as well as on make, the LED will
flash when the switch is closed, then again when it's opened.
The fix:
. | <--O--+-----+-------+-------+
. |S1 | | 8| |
.VCCIN>--O [100K] [Rt] +---+---+ |
. | | 2|_ Vcc _|4 |
. +-----|--O|T R|O--+
. | | 6| | |
. | +---|TH OUT|---|----+
. | | 7|_ |3 | |
. [100nF] +--O|D 7555| | [Rled]
. | +| | GND | [10K] |
. | [Ct] +---+---+ | [LED]
. | | 1| | |K
.GND>------------+-----+-------+-------+----+