I need help! Trying to use 555 timer to pulse but input will be steady state.

[[email protected]]

I am trying to figure out a cct which uses a 555 timer to send a pulse
to imitate pressing of a button when I turn the ignition on. I want the
pulse to be about one second long.
The thing is, when I start the car the trigger will always be at a
steady state, not a pulsed input.

I have tried this, but the output just stays low, if the trigger is
steady state low.

I was thinking I could use the momentary position of the ignition
switch which turns the motor and it would be like an trigger pulse, but
I wish to use he same circuit more than once , and when the car is
already running.

Anyone any ideas on this?

Thanks.

 

[D from BC]

I am trying to figure out a cct which uses a 555 timer to send a
pulse
to imitate pressing of a button when I turn the ignition on. I
want the
pulse to be about one second long.
The thing is, when I start the car the trigger will always be at
a
steady state, not a pulsed input.

I have tried this, but the output just stays low, if the trigger
is
steady state low.

I was thinking I could use the momentary position of the
ignition
switch which turns the motor and it would be like an trigger
pulse, but
I wish to use he same circuit more than once , and when the car
is
already running.

Anyone any ideas on this?

Thanks.

..
-------------
Oh no..hope you're not making a car bomb

See 555 app notes.. You're looking for positive edge triggering.

Or...just skip that boring way and use a microcontroller

D
------

 

[jasen]

I am trying to figure out a cct which uses a 555 timer to send a pulse
to imitate pressing of a button when I turn the ignition on. I want the
pulse to be about one second long.
The thing is, when I start the car the trigger will always be at a
steady state, not a pulsed input.

I have tried this, but the output just stays low, if the trigger is
steady state low.

tried what?

Anyone any ideas on this?

just one: (view with fixed font)

ign
|
.--------------------+
| |
| . . . .|. . . .
| . VCC(8) .
| . .
+--------------RES(4) OUT(3)------ out
| . 555 .
+--[100K]--+---TH(6) DIS(7)--
|   | . .
`--|<----+-+---TR(2) CV(5)--
| . .
|+ . GND(1) .
10uF=== . . . .|. . . .
| |
--+-----------+--------- ground

Bye.
Jasen

 

[ehsjr]

I am trying to figure out a cct which uses a 555 timer to send a pulse
to imitate pressing of a button when I turn the ignition on. I want the
pulse to be about one second long.
The thing is, when I start the car the trigger will always be at a
steady state, not a pulsed input.

I have tried this, but the output just stays low, if the trigger is
steady state low.

I was thinking I could use the momentary position of the ignition
switch which turns the motor and it would be like an trigger pulse, but
I wish to use he same circuit more than once , and when the car is
already running.

Anyone any ideas on this?

Thanks.

Here's one way:

Ignition
Switch
/
+12---o o-----+------+
|+ |
[100uF] |
| [10K]
[Rly] | |> |
| | | |
Gnd -----------+------+---o o----> To 555 pin 2

That will give you a trigger pulse to the 555,
rather than a steady level. You'll likely get
several pulses due to relay contact bounce, but
the bouncing will be finished in less than .1
seconds, so it's irrelevant.

Ed

 

[default]

I am trying to figure out a cct which uses a 555 timer to send a pulse
to imitate pressing of a button when I turn the ignition on. I want the
pulse to be about one second long.
The thing is, when I start the car the trigger will always be at a
steady state, not a pulsed input.

I have tried this, but the output just stays low, if the trigger is
steady state low.

I was thinking I could use the momentary position of the ignition
switch which turns the motor and it would be like an trigger pulse, but
I wish to use he same circuit more than once , and when the car is
already running.

Anyone any ideas on this?

Thanks.

The datasheet for the standard 555 shows a circuit that capacitive
couples the trigger in on pin 6 (I think that's it) of the mono
stable. Cap is .01 uf and there's a 10 K pull-up resistor on either
side of the cap.

The low trigger toggles the mono stable through one timing cycle and
the input trigger on the cap can remain low thereafter.

 

[[email protected]]

The datasheet for the standard 555 shows a circuit that capacitive
couples the trigger in on pin 6 (I think that's it) of the mono
stable. Cap is .01 uf and there's a 10 K pull-up resistor on either
side of the cap.

The low trigger toggles the mono stable through one timing cycle and
the input trigger on the cap can remain low thereafter.

Thanks everyone, although, I cannot read those ccts even with a fixed
font. I know it took a lot of work to type them in, and I am grateful.

Where do I find the standard 555 datasheet so I can look at this
capacitative coupling cct.
Thanks again.

 

[default]

Where do I find the standard 555 datasheet so I can look at this
capacitative coupling cct.
Thanks again.

http://www.williamson-labs.com/555_apps.htm has it first example on
the page

http://www.doctronics.co.uk/pdf_files/555an.pdf pretty pictures has
it on page 3 Two pull up resistors and a .001 uf cap

National Semiconductor has their data and applications on searchable
CDrom for free, and on line. Too lazy to look it up so I picked the
first hit that matched my search terms <555 application notes >

FYI - all this stuff is on line - goggle for it

 

[Winfield Hill]

I am trying to figure out a cct which uses a 555 timer to send a pulse
to imitate pressing of a button when I turn the ignition on. I want the
pulse to be about one second long.
The thing is, when I start the car the trigger will always be at a
steady state, not a pulsed input.

I have tried this, but the output just stays low, if the trigger is
steady state low.

I was thinking I could use the momentary position of the ignition
switch which turns the motor and it would be like an trigger pulse, but
I wish to use he same circuit more than once , and when the car is
already running.

Here's one way:

Ignition
Switch
/
+12---o o-----+------+
|+ |
[100uF] |
| [10K]
[Rly] | |> |
| | | |
Gnd -----------+------+---o o----> To 555 pin 2

That will give you a trigger pulse to the 555,
rather than a steady level. You'll likely get
several pulses due to relay contact bounce, but
the bouncing will be finished in less than .1
seconds, so it's irrelevant.

Thanks Ed, but that's rather painful with the relay...

jasen showed an attractive approach, using switched
power. That's a good idea, and should be considered.

We usually use continuously-powered circuits, maybe
because they're easier to think about. In the case of a
555 timer chip, we need to AC couple the trigger signal.

Here's an example:

battery
|
,------+---+--------------+----------,
| | | | 555 |
| | | . . . . . . . . . |
| | 100k . VCC(8) . |
| | | .___ . |
IGN | | +------.DIS(4) OUT(3).--| ---- out
| 22k 22k | . ___ . |
| | | +------.THRES(6) RES(4).--'
| | 0.01 | | .____ .
22k +-||---+-- | -----.TRIG(2) CV(5).--
| | | . .
| |/ _|_+ . GND(1) .
'----| --- . . . . . . . . .
|\v | 10uF |
| | |
---+----------+--------------+------- ground

The Ignition signal is positive going, but the 555 wants
a negative trigger, so we have to add an inverter. This
makes this approach less attractive than jasen's circuit.

ign
|

.--------------------+
| |
| . . . .|. . . .
| . VCC(8)
| . .
+--------------RES(4) OUT(3)------ out
| . 555 .
+--[100K]--+---TH(6) DIS(7)-
| | . .
`--|<----+-+---TR(2) CV(5)--
| . .
|+ . GND(1) .
10uF=== . . . .|. . . .
| |
--+-----------+--------- ground

 

[ehsjr]

I am trying to figure out a cct which uses a 555 timer to send a pulse
to imitate pressing of a button when I turn the ignition on. I want the
pulse to be about one second long.
The thing is, when I start the car the trigger will always be at a
steady state, not a pulsed input.

I have tried this, but the output just stays low, if the trigger is
steady state low.

I was thinking I could use the momentary position of the ignition
switch which turns the motor and it would be like an trigger pulse, but
I wish to use he same circuit more than once , and when the car is
already running.

Here's one way:

Ignition
Switch
/
+12---o o-----+------+
|+ |
[100uF] |
| [10K]
[Rly] | |> |
| | | |
Gnd -----------+------+---o o----> To 555 pin 2

That will give you a trigger pulse to the 555,
rather than a steady level. You'll likely get
several pulses due to relay contact bounce, but
the bouncing will be finished in less than .1
seconds, so it's irrelevant.

Thanks Ed, but that's rather painful with the relay...

Yup, it's ugly.

jasen showed an attractive approach, using switched
power. That's a good idea, and should be considered.

His stuff is always good, as is yours, of course.

Thanks,
Ed

We usually use continuously-powered circuits, maybe
because they're easier to think about. In the case of a
555 timer chip, we need to AC couple the trigger signal.

Here's an example:

battery
|
,------+---+--------------+----------,
| | | | 555 |
| | | . . . . . . . . . |
| | 100k . VCC(8) . |
| | | .___ . |
IGN | | +------.DIS(4) OUT(3).--| ---- out
| 22k 22k | . ___ . |
| | | +------.THRES(6) RES(4).--'
| | 0.01 | | .____ .
22k +-||---+-- | -----.TRIG(2) CV(5).--
| | | . .
| |/ _|_+ . GND(1) .
'----| --- . . . . . . . . .
|\v | 10uF |
| | |
---+----------+--------------+------- ground

The Ignition signal is positive going, but the 555 wants
a negative trigger, so we have to add an inverter. This
makes this approach less attractive than jasen's circuit.

ign
|

.--------------------+
| |
| . . . .|. . . .
| . VCC(8)
| . .
+--------------RES(4) OUT(3)------ out
| . 555 .
+--[100K]--+---TH(6) DIS(7)-
| | . .
`--|<----+-+---TR(2) CV(5)--
| . .
|+ . GND(1) .
10uF=== . . . .|. . . .
| |
--+-----------+--------- ground

 

[[email protected]]

[email protected] wrote:

I am trying to figure out a cct which uses a 555 timer to send a pulse
to imitate pressing of a button when I turn the ignition on. I want the
pulse to be about one second long.
The thing is, when I start the car the trigger will always be at a
steady state, not a pulsed input.

I have tried this, but the output just stays low, if the trigger is
steady state low.

I was thinking I could use the momentary position of the ignition
switch which turns the motor and it would be like an trigger pulse, but
I wish to use he same circuit more than once , and when the car is
already running.

Here's one way:

Ignition
Switch
/
+12---o o-----+------+
|+ |
[100uF] |
| [10K]
[Rly] | |> |
| | | |
Gnd -----------+------+---o o----> To 555 pin 2

That will give you a trigger pulse to the 555,
rather than a steady level. You'll likely get
several pulses due to relay contact bounce, but
the bouncing will be finished in less than .1
seconds, so it's irrelevant.

Thanks Ed, but that's rather painful with the relay...

Yup, it's ugly.

jasen showed an attractive approach, using switched
power. That's a good idea, and should be considered.

His stuff is always good, as is yours, of course.

Thanks,
Ed

We usually use continuously-powered circuits, maybe
because they're easier to think about. In the case of a
555 timer chip, we need to AC couple the trigger signal.

Here's an example:

battery
|
,------+---+--------------+----------,
| | | | 555 |
| | | . . . . . . . . . |
| | 100k . VCC(8) . |
| | | .___ . |
IGN | | +------.DIS(4) OUT(3).--| ---- out
| 22k 22k | . ___ . |
| | | +------.THRES(6) RES(4).--'
| | 0.01 | | .____ .
22k +-||---+-- | -----.TRIG(2) CV(5).--
| | | . .
| |/ _|_+ . GND(1) .
'----| --- . . . . . . . . .
|\v | 10uF |
| | |
---+----------+--------------+------- ground

The Ignition signal is positive going, but the 555 wants
a negative trigger, so we have to add an inverter. This
makes this approach less attractive than jasen's circuit.

ign
|

.--------------------+
| |
| . . . .|. . . .
| . VCC(8)
| . .
+--------------RES(4) OUT(3)------ out
| . 555 .
+--[100K]--+---TH(6) DIS(7)-
| | . .
`--|<----+-+---TR(2) CV(5)--
| . .
|+ . GND(1) .
10uF=== . . . .|. . . .
| |
--+-----------+--------- ground

Is there any chance one of you guys could elaborate or draw a proper
pic and put a link to the photo site where the picture would be located
so I could look at it?

Thanks again.

 

[Winfield Hill]

ehsjr wrote:

Here's one way:

Ignition
Switch
/
+12---o o-----+------+
|+ |
[100uF] |
| [10K]
[Rly] | |> |
| | | |
Gnd -----------+------+---o o----> To 555 pin 2

That will give you a trigger pulse to the 555,

We usually use continuously-powered circuits, maybe
because they're easier to think about. In the case of a
555 timer chip, we need to AC couple the trigger signal.

Here's an example:

battery
|
,------+---+--------------+----------,
| | | | 555 |
| | | . . . . . . . . . |
| | 100k . VCC(8) . |
| | | .___ . |
IGN | | +------.DIS(4) OUT(3).--| ---- out
| 22k 22k | . ___ . |
| | | +------.THRES(6) RES(4).--'
| | 0.01 | | .____ .
22k +-||---+-- | -----.TRIG(2) CV(5).--
| | | . .
| |/ _|_+ . GND(1) .
'----| --- . . . . . . . . .
|\v | 10uF |
| | |
---+----------+--------------+------- ground

The Ignition signal is positive going, but the 555 wants
a negative trigger, so we have to add an inverter. This
makes this approach less attractive than jasen's circuit.

ign
|

.--------------------+
| |
| . . . .|. . . .
| . VCC(8)
| . .
+--------------RES(4) OUT(3)------ out
| . 555 .
+--[100K]--+---TH(6) DIS(7)-
| | . .
`--|<----+-+---TR(2) CV(5)--
| . .
|+ . GND(1) .
10uF=== . . . .|. . . .
| |
--+-----------+--------- ground

Is there any chance one of you guys could elaborate or draw a proper
pic and put a link to the photo site where the picture would be located
so I could look at it?

You can easiiy see ASCII drawings if you tell your viewer
or browser to use a fixed font like Courier. If that's too
painful, you can copy the text into a simple editor like
Notepad, and view it with a fixed font, and print it as well.

I've shortened the text above to just the three drawings.

 

[Winfield Hill]

ehsjr wrote:

Here's one way:

Ignition
Switch
/
+12---o o-----+------+
|+ |
[100uF] |
| [10K]
[Rly] | |> |
| | | |
Gnd -----------+------+---o o----> To 555 pin 2

That will give you a trigger pulse to the 555,

We usually use continuously-powered circuits, maybe
because they're easier to think about. In the case of a
555 timer chip, we need to AC couple the trigger signal.

Here's an example:

battery
|
,------+---+--------------+----------,
| | | | 555 |
| | | . . . . . . . . . |
| | 100k . VCC(8) . |
| | | .___ . |
IGN | | +------.DIS(4) OUT(3).--| ---- out
| 22k 22k | . ___ . |
| | | +------.THRES(6) RES(4).--'
| | 0.01 | | .____ .
22k +-||---+-- | -----.TRIG(2) CV(5).--
| | | . .
| |/ _|_+ . GND(1) .
'----| --- . . . . . . . . .
|\v | 10uF |
| | |
---+----------+--------------+------- ground

The Ignition signal is positive going, but the 555 wants
a negative trigger, so we have to add an inverter. This
makes this approach less attractive than jasen's circuit.

ign
|

.--------------------+
| |
| . . . .|. . . .
| . VCC(8)
| . .
+--------------RES(4) OUT(3)------ out
| . 555 .
+--[100K]--+---TH(6) DIS(7)-
| | . .
`--|<----+-+---TR(2) CV(5)--
| . .
|+ . GND(1) .
10uF=== . . . .|. . . .
| |
--+-----------+--------- ground

Is there any chance one of you guys could elaborate or draw a proper
pic and put a link to the photo site where the picture would be located
so I could look at it?

You can easiiy see ASCII drawings if you tell your viewer
or browser to use a fixed font like Courier. If that's too
painful, you can copy the text into a simple editor like
Notepad, and view it with a fixed font, and print it as well.

I've shortened the text above to just the three drawings.

 

[[email protected]]

Winfield Hill wrote:
ehsjr wrote:

Here's one way:

Ignition
Switch
/
+12---o o-----+------+
|+ |
[100uF] |
| [10K]
[Rly] | |> |
| | | |
Gnd -----------+------+---o o----> To 555 pin 2

That will give you a trigger pulse to the 555,

We usually use continuously-powered circuits, maybe
because they're easier to think about. In the case of a
555 timer chip, we need to AC couple the trigger signal.

Here's an example:

battery
|
,------+---+--------------+----------,
| | | | 555 |
| | | . . . . . . . . . |
| | 100k . VCC(8) . |
| | | .___ . |
IGN | | +------.DIS(4) OUT(3).--| ---- out
| 22k 22k | . ___ . |
| | | +------.THRES(6) RES(4).--'
| | 0.01 | | .____ .
22k +-||---+-- | -----.TRIG(2) CV(5).--
| | | . .
| |/ _|_+ . GND(1) .
'----| --- . . . . . . . . .
|\v | 10uF |
| | |
---+----------+--------------+------- ground

The Ignition signal is positive going, but the 555 wants
a negative trigger, so we have to add an inverter. This
makes this approach less attractive than jasen's circuit.

ign
|

.--------------------+
| |
| . . . .|. . . .
| . VCC(8)
| . .
+--------------RES(4) OUT(3)------ out
| . 555 .
+--[100K]--+---TH(6) DIS(7)-
| | . .
`--|<----+-+---TR(2) CV(5)--
| . .
|+ . GND(1) .
10uF=== . . . .|. . . .
| |
--+-----------+--------- ground

Is there any chance one of you guys could elaborate or draw a proper
pic and put a link to the photo site where the picture would be located
so I could look at it?

You can easiiy see ASCII drawings if you tell your viewer
or browser to use a fixed font like Courier. If that's too
painful, you can copy the text into a simple editor like
Notepad, and view it with a fixed font, and print it as well.

I've shortened the text above to just the three drawings.

Hey, that 2nd example works a treat.

Thanks very much.

 

[JeffM]

Is there any chance one of you guys could elaborate
or draw a proper pic[...]so I could look at it?

-- Ways for Google Groupers to view ASCII graphics --
1) As Win said,
cut & paste into something that uses a monospaced font natively.
or
2) Click **show options** in the header of the post you wish to view
then click **Show original**.
http://groups.google.com/group/sci.electronics.design/msg/b9684d43e1397235
or
3) Go to the top of the page and click **Fixed font**.[1]
http://groups.google.com/group/sci....3e1397235?q=555+RES+TRIG+zz-zz+qq+____+&fwc=1
..
..
or
4) You could start accessing Usenet
http://66.102.9.104/search?q=cache:...oogle-cannot-muster-*-*-*-*-*-*-*-*-*-*-*-*-*
the way the majority of people do: with a newsreader:
http://66.102.9.104/search?q=cache:...te+zz+zz+Seamonkey+Thunderbird+Mozilla+40tude
..
..
[1] Before exiting the Google page
you will likely want to go back and click **Proportional font**
so that pages you view in the future will appear in the default font.