Hi,

I have a simple 555 delayed timer and I wish to light up a LED when
the timer starts and a relay off. At the end of the interval the LED
should be off and the relay on. I made a simple circuit as follows:

+------------+---+---------+---+------------+---------+--
VCC
| | | | | .-. |
| | | .-. | | | |
.-. |4 |8 | |<-+ | |470 |
| | .-------. | |1M '-' |
| |10k | | '-' | |
'-' | |3 | | |
| | |------------+ | |
| 2| 555 |7 | | led V -> |
o----------| |--o----o | - |
| | |6 | | | | | \
|+ | |--+ | | +---+ |_ o o
=== '-------' | | | | )|
/-\33u |1 |5 47u|+ | ___ |/ | )|
relay
| | --- --- +--|___|--| | _)|
| | ---10n /-\ 10k |> | +--
| | | | | | |
GND GND GND GND | | |/
| +-|
| |>
| |
| |
+-------o
|
GND
(created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)

But the LED stays ON at the end of the interval when the relay is
switched ON. I have to add an iverter and modified the circuit as
below:

VCC -----o---------o---o------------o---------
o------------o
| | | |
| |
| .-. | .-. |
\ .-.
|8 | |<-+ | | |_ o
o | |
.------. | |1M 10k|
| )| | |470
| | '-' '-' )|
relay '-'
| |3 | |
_)| |
| |------------+ |
| |
| 555 |7 | | |
| LED V ->
| |--o----o | |
| -
| |6 | | | | | |
\ |
| |--+ | | +---+ o---|
>O------
'------' | | | | | |/
|5 47u|+ | ___ |/ | |
4069
--- --- +--|___|--| | |
---10n /-\ 10k |> | +-+
| | | | |
GND GND | | |/
| +-|
| |>
| |
| |
+-------o
|
GND
(created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)

Is there any way not to light up the LED when the relay is switched on
with just the two transistors?

Allen

On Aug 28, 6:11 am, Allen Bong <allenbsf6...@gmail.com> wrote:
> Hi,
>
> I have a simple 555 delayed timer and I wish to light up a LED when
> the timer starts and a relay off. At the end of the interval the LED
> should be off and the relay on. I made a simple circuit as follows:
>
> +------------+---+---------+---+------------+---------+--
> VCC
> | | | | | .-. |
> | | | .-. | | | |
> .-. |4 |8 | |<-+ | |470 |
> | | .-------. | |1M '-' |
> | |10k | | '-' | |
> '-' | |3 | | |
> | | |------------+ | |
> | 2| 555 |7 | | led V -> |
> o----------| |--o----o | - |
> | | |6 | | | | | \
> |+ | |--+ | | +---+ |_ o o
> === '-------' | | | | )|
> /-\33u |1 |5 47u|+ | ___ |/ | )|
> relay
> | | --- --- +--|___|--| | _)|
> | | ---10n /-\ 10k |> | +--
> | | | | | | |
> GND GND GND GND | | |/
> | +-|
> | |>
> | |
> | |
> +-------o
> |
> GND
> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> But the LED stays ON at the end of the interval when the relay is
> switched ON. I have to add an iverter and modified the circuit as
> below:
>
> VCC -----o---------o---o------------o---------
> o------------o
> | | | |
> | |
> | .-. | .-. |
> \ .-.
> |8 | |<-+ | | |_ o
> o | |
> .------. | |1M 10k|
> | )| | |470
> | | '-' '-' )|
> relay '-'
> | |3 | |
> _)| |
> | |------------+ |
> | |
> | 555 |7 | | |
> | LED V ->
> | |--o----o | |
> | -
> | |6 | | | | | |
> \ |
> | |--+ | | +---+ o---|>O------
>
> '------' | | | | | |/
> |5 47u|+ | ___ |/ | |
> 4069
> --- --- +--|___|--| | |
> ---10n /-\ 10k |> | +-+
> | | | | |
> GND GND | | |/
> | +-|
> | |>
> | |
> | |
> +-------o
> |
> GND
> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> Is there any way not to light up the LED when the relay is switched on
> with just the two transistors?
>
> Allen

Sorry about the screw-up, here is the second circuit again:





VCC -----o---------o---o------------o---------o------------o
| | | | | |
| .-. | .-. | \ .-.
|8 | |<-+ | | |_ o o | |
.------. | |1M 10k| | )| | |470
| | '-' '-' )|relay '-'
| |3 | | _)| |
| |------------+ | | |
| 555 |7 | | | | LED V ->
| |--o----o | | | -
| |6 | | | | | |\ |
| |--+ | | +---+ o---| >O------
'------' | | | | | |/
|5 47u|+ | ___ |/ | | 4069
--- --- +--|___|--| | |
---10n /-\ 10k |> | +-+
| | | | |
GND GND | | |/
| +-|
| |>
| |
| |
+-------o
|
GND
(created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)

Allen Bong wrote:
> Hi,
>
> I have a simple 555 delayed timer and I wish to light up a LED when
> the timer starts and a relay off. At the end of the interval the LED
> should be off and the relay on. I made a simple circuit as follows:
>
> +------------+---+---------+---+------------+---------+--
> VCC
> | | | | | .-. |
> | | | .-. | | | |
> .-. |4 |8 | |<-+ | |470 |
> | | .-------. | |1M '-' |
> | |10k | | '-' | |
> '-' | |3 | | |
> | | |------------+ | |
> | 2| 555 |7 | | led V -> |
> o----------| |--o----o | - |
> | | |6 | | | | | \
> |+ | |--+ | | +---+ |_ o o
> === '-------' | | | | )|
> /-\33u |1 |5 47u|+ | ___ |/ | )|
> relay
> | | --- --- +--|___|--| | _)|
> | | ---10n /-\ 10k |> | +--
> | | | | | | |
> GND GND GND GND | | |/
> | +-|
> | |>
> | |
> | |
> +-------o
> |
> GND
> (created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)
>
> But the LED stays ON at the end of the interval when the relay is
> switched ON. I have to add an iverter and modified the circuit as
> below:
>
> VCC -----o---------o---o------------o---------
> o------------o
> | | | |
> | |
> | .-. | .-. |
> \ .-.
> |8 | |<-+ | | |_ o
> o | |
> .------. | |1M 10k|
> | )| | |470
> | | '-' '-' )|
> relay '-'
> | |3 | |
> _)| |
> | |------------+ |
> | |
> | 555 |7 | | |
> | LED V ->
> | |--o----o | |
> | -
> | |6 | | | | | |
> \ |
> | |--+ | | +---+ o---|
>
>>O------
>
> '------' | | | | | |/
> |5 47u|+ | ___ |/ | |
> 4069
> --- --- +--|___|--| | |
> ---10n /-\ 10k |> | +-+
> | | | | |
> GND GND | | |/
> | +-|
> | |>
> | |
> | |
> +-------o
> |
> GND
> (created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)
>
> Is there any way not to light up the LED when the relay is switched on
> with just the two transistors?
>
> Allen
>

You can get a lot simpler:

+12 ------------------+------+
| |
[Relay] [D2]
D1 | |a
555 pin3]----+---|<---+------+
| a
[470R]
|
[LED]
|
Gnd

If you want to use a transistor driver for the relay:

+12 ----------------------+
|
/e
[555 pin3]---+---[1K]---| PNP
| \c
[470R] |
| +------+
[LED] | |
| [Relay] [D1]
| | |a
Gnd ---------+------------+------+

In either circuit, when the 555 is "on" there is + at
pin 3. That lights the LED, and keeps the relay off.
When the 555 is "off", there is - at pin three. That
keeps the LED off and the relay "on" (energized).

Ed

On Mon, 27 Aug 2007 15:18:47 -0700, Allen Bong
<allenbsf6502@gmail.com> wrote:

>On Aug 28, 6:11 am, Allen Bong <allenbsf6...@gmail.com> wrote:
>> Hi,
>>
>> I have a simple 555 delayed timer and I wish to light up a LED when
>> the timer starts and a relay off. At the end of the interval the LED
>> should be off and the relay on. I made a simple circuit as follows:
>>
>> +------------+---+---------+---+------------+---------+--
>> VCC
>> | | | | | .-. |
>> | | | .-. | | | |
>> .-. |4 |8 | |<-+ | |470 |
>> | | .-------. | |1M '-' |
>> | |10k | | '-' | |
>> '-' | |3 | | |
>> | | |------------+ | |
>> | 2| 555 |7 | | led V -> |
>> o----------| |--o----o | - |
>> | | |6 | | | | | \
>> |+ | |--+ | | +---+ |_ o o
>> === '-------' | | | | )|
>> /-\33u |1 |5 47u|+ | ___ |/ | )|
>> relay
>> | | --- --- +--|___|--| | _)|
>> | | ---10n /-\ 10k |> | +--
>> | | | | | | |
>> GND GND GND GND | | |/
>> | +-|
>> | |>
>> | |
>> | |
>> +-------o
>> |
>> GND
>> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>>
>> But the LED stays ON at the end of the interval when the relay is
>> switched ON. I have to add an iverter and modified the circuit as
>> below:
>>
>> VCC -----o---------o---o------------o---------
>> o------------o
>> | | | |
>> | |
>> | .-. | .-. |
>> \ .-.
>> |8 | |<-+ | | |_ o
>> o | |
>> .------. | |1M 10k|
>> | )| | |470
>> | | '-' '-' )|
>> relay '-'
>> | |3 | |
>> _)| |
>> | |------------+ |
>> | |
>> | 555 |7 | | |
>> | LED V ->
>> | |--o----o | |
>> | -
>> | |6 | | | | | |
>> \ |
>> | |--+ | | +---+ o---|>O------
>>
>> '------' | | | | | |/
>> |5 47u|+ | ___ |/ | |
>> 4069
>> --- --- +--|___|--| | |
>> ---10n /-\ 10k |> | +-+
>> | | | | |
>> GND GND | | |/
>> | +-|
>> | |>
>> | |
>> | |
>> +-------o
>> |
>> GND
>> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>>
>> Is there any way not to light up the LED when the relay is switched on
>> with just the two transistors?
>>
>> Allen
>
>Sorry about the screw-up, here is the second circuit again:
>
>
>
>
>
> VCC -----o---------o---o------------o---------o------------o
> | | | | | |
> | .-. | .-. | \ .-.
> |8 | |<-+ | | |_ o o | |
> .------. | |1M 10k| | )| | |470
> | | '-' '-' )|relay '-'
> | |3 | | _)| |
> | |------------+ | | |
> | 555 |7 | | | | LED V ->
> | |--o----o | | | -
> | |6 | | | | | |\ |
> | |--+ | | +---+ o---| >O------
> '------' | | | | | |/
> |5 47u|+ | ___ |/ | | 4069
> --- --- +--|___|--| | |
> ---10n /-\ 10k |> | +-+
> | | | | |
> GND GND | | |/
> | +-|
> | |>
> | |
> | |
> +-------o
> |
> GND
>(created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)

---
So, it looks like you want the relay to be ON and the LED to be OFF
when power is down, and then when power comes up you want the relay
to turn OFF and the LED to turn ON for a certain amount of time and
then when that time expires you want the relay to turn ON and the
LED to turn OFF for as long as power is up?


--
JF

On Aug 28, 8:25 am, John Fields <jfie...@austininstruments.com> wrote:
> On Mon, 27 Aug 2007 15:18:47 -0700, Allen Bong
>
>
>
>
>
> <allenbsf6...@gmail.com> wrote:
> >On Aug 28, 6:11 am, Allen Bong <allenbsf6...@gmail.com> wrote:
> >> Hi,
>
> >> I have a simple 555 delayed timer and I wish to light up a LED when
> >> the timer starts and a relay off. At the end of the interval the LED
> >> should be off and the relay on. I made a simple circuit as follows:
>
> >> +------------+---+---------+---+------------+---------+--
> >> VCC
> >> | | | | | .-. |
> >> | | | .-. | | | |
> >> .-. |4 |8 | |<-+ | |470 |
> >> | | .-------. | |1M '-' |
> >> | |10k | | '-' | |
> >> '-' | |3 | | |
> >> | | |------------+ | |
> >> | 2| 555 |7 | | led V -> |
> >> o----------| |--o----o | - |
> >> | | |6 | | | | | \
> >> |+ | |--+ | | +---+ |_ o o
> >> === '-------' | | | | )|
> >> /-\33u |1 |5 47u|+ | ___ |/ | )|
> >> relay
> >> | | --- --- +--|___|--| | _)|
> >> | | ---10n /-\ 10k |> | +--
> >> | | | | | | |
> >> GND GND GND GND | | |/
> >> | +-|
> >> | |>
> >> | |
> >> | |
> >> +-------o
> >> |
> >> GND
> >> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> >> But the LED stays ON at the end of the interval when the relay is
> >> switched ON. I have to add an iverter and modified the circuit as
> >> below:
>
> >> VCC -----o---------o---o------------o---------
> >> o------------o
> >> | | | |
> >> | |
> >> | .-. | .-. |
> >> \ .-.
> >> |8 | |<-+ | | |_ o
> >> o | |
> >> .------. | |1M 10k|
> >> | )| | |470
> >> | | '-' '-' )|
> >> relay '-'
> >> | |3 | |
> >> _)| |
> >> | |------------+ |
> >> | |
> >> | 555 |7 | | |
> >> | LED V ->
> >> | |--o----o | |
> >> | -
> >> | |6 | | | | | |
> >> \ |
> >> | |--+ | | +---+ o---|>O------
>
> >> '------' | | | | | |/
> >> |5 47u|+ | ___ |/ | |
> >> 4069
> >> --- --- +--|___|--| | |
> >> ---10n /-\ 10k |> | +-+
> >> | | | | |
> >> GND GND | | |/
> >> | +-|
> >> | |>
> >> | |
> >> | |
> >> +-------o
> >> |
> >> GND
> >> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> >> Is there any way not to light up the LED when the relay is switched on
> >> with just the two transistors?
>
> >> Allen
>
> >Sorry about the screw-up, here is the second circuit again:
>
> > VCC -----o---------o---o------------o---------o------------o
> > | | | | | |
> > | .-. | .-. | \ .-.
> > |8 | |<-+ | | |_ o o | |
> > .------. | |1M 10k| | )| | |470
> > | | '-' '-' )|relay '-'
> > | |3 | | _)| |
> > | |------------+ | | |
> > | 555 |7 | | | | LED V ->
> > | |--o----o | | | -
> > | |6 | | | | | |\ |
> > | |--+ | | +---+ o---| >O------
> > '------' | | | | | |/
> > |5 47u|+ | ___ |/ | | 4069
> > --- --- +--|___|--| | |
> > ---10n /-\ 10k |> | +-+
> > | | | | |
> > GND GND | | |/
> > | +-|
> > | |>
> > | |
> > | |
> > +-------o
> > |
> > GND
> >(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> ---
> So, it looks like you want the relay to be ON and the LED to be OFF
> when power is down, and then when power comes up you want the relay
> to turn OFF and the LED to turn ON for a certain amount of time and
> then when that time expires you want the relay to turn ON and the
> LED to turn OFF for as long as power is up?
>
> --
> JF- Hide quoted text -
>
> - Show quoted text -

No, when the power is up the led will be ON and relay is OFF for a
time determined by the 1M preset. When the time expires, the LED will
be off and the relay turns ON. It operates exactly like a delay timer
for electrical controls except that I have to put 8 of them on a PCB.

When the power is off everything turns OFF.


Allen

On Aug 28, 8:19 am, ehsjr <eh...@bellatlantic.net> wrote:
> Allen Bong wrote:
> > Hi,
>
> > I have a simple 555 delayed timer and I wish to light up a LED when
> > the timer starts and a relay off. At the end of the interval the LED
> > should be off and the relay on. I made a simple circuit as follows:
>
> > +------------+---+---------+---+------------+---------+--
> > VCC
> > | | | | | .-. |
> > | | | .-. | | | |
> > .-. |4 |8 | |<-+ | |470 |
> > | | .-------. | |1M '-' |
> > | |10k | | '-' | |
> > '-' | |3 | | |
> > | | |------------+ | |
> > | 2| 555 |7 | | led V -> |
> > o----------| |--o----o | - |
> > | | |6 | | | | | \
> > |+ | |--+ | | +---+ |_ o o
> > === '-------' | | | | )|
> > /-\33u |1 |5 47u|+ | ___ |/ | )|
> > relay
> > | | --- --- +--|___|--| | _)|
> > | | ---10n /-\ 10k |> | +--
> > | | | | | | |
> > GND GND GND GND | | |/
> > | +-|
> > | |>
> > | |
> > | |
> > +-------o
> > |
> > GND
> > (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> > But the LED stays ON at the end of the interval when the relay is
> > switched ON. I have to add an iverter and modified the circuit as
> > below:
>
> > VCC -----o---------o---o------------o---------
> > o------------o
> > | | | |
> > | |
> > | .-. | .-. |
> > \ .-.
> > |8 | |<-+ | | |_ o
> > o | |
> > .------. | |1M 10k|
> > | )| | |470
> > | | '-' '-' )|
> > relay '-'
> > | |3 | |
> > _)| |
> > | |------------+ |
> > | |
> > | 555 |7 | | |
> > | LED V ->
> > | |--o----o | |
> > | -
> > | |6 | | | | | |
> > \ |
> > | |--+ | | +---+ o---|
>
> >>O------
>
> > '------' | | | | | |/
> > |5 47u|+ | ___ |/ | |
> > 4069
> > --- --- +--|___|--| | |
> > ---10n /-\ 10k |> | +-+
> > | | | | |
> > GND GND | | |/
> > | +-|
> > | |>
> > | |
> > | |
> > +-------o
> > |
> > GND
> > (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> > Is there any way not to light up the LED when the relay is switched on
> > with just the two transistors?
>
> > Allen
>
> You can get a lot simpler:
>
> +12 ------------------+------+
> | |
> [Relay] [D2]
> D1 | |a
> 555 pin3]----+---|<---+------+
> | a
> [470R]
> |
> [LED]
> |
> Gnd
>
> If you want to use a transistor driver for the relay:
>
> +12 ----------------------+
> |
> /e
> [555 pin3]---+---[1K]---| PNP
> | \c
> [470R] |
> | +------+
> [LED] | |
> | [Relay] [D1]
> | | |a
> Gnd ---------+------------+------+
>
> In either circuit, when the 555 is "on" there is + at
> pin 3. That lights the LED, and keeps the relay off.
> When the 555 is "off", there is - at pin three. That
> keeps the LED off and the relay "on" (energized).
>
> Ed- Hide quoted text -
>
> - Show quoted text -

Thanks Ed, that seems to have solved all but one of my problems.
Based on circuit #1, do you think the 555 would kick start reliably
every time the power is switched ON?


Regards,

Allen

On Tue, 28 Aug 2007 00:14:57 -0700, Allen Bong
<allenbsf6502@gmail.com> wrote:


>Thanks Ed, that seems to have solved all but one of my problems.
>Based on circuit #1, do you think the 555 would kick start reliably
>every time the power is switched ON?

---
With RESET- tied to Vcc, in order to do that you'll have to make
sure that the TRIGGER- input stays below 1/3Vcc until after the
RESET- input rises above 1.0V.

Additionally, the TRIGGER input must rise to >= 2/3Vcc before the
one-shot times out.


--
JF

On Aug 28, 11:42 pm, John Fields <jfie...@austininstruments.com>
wrote:
> On Tue, 28 Aug 2007 00:14:57 -0700, Allen Bong
>
> <allenbsf6...@gmail.com> wrote:
> >Thanks Ed, that seems to have solved all but one of my problems.
> >Based on circuit #1, do you think the 555 would kick start reliably
> >every time the power is switched ON?
>
> ---
> With RESET- tied to Vcc, in order to do that you'll have to make
> sure that the TRIGGER- input stays below 1/3Vcc until after the
> RESET- input rises above 1.0V.
>
> Additionally, the TRIGGER input must rise to >= 2/3Vcc before the
> one-shot times out.
>
> --
> JF

Thanks very much John,

I'll recalculated the values of the components on pins 2, 6 and 7 to
make sure the interval of the TRIGGER is shorter than the minimum time
interval of the one-shot.

Allen