555 used as a delayed pulse generator?

T

Tristar

Jan 1, 1970
0
I'm looking to set us a simple way to turn something on after 10 seconds. The
resulting output after the end of the 10 seconds needs to be a momentary pulse
and not stay in a closed position.

-----------------------------------------------------------------------^-

Like this.

Circuit is started with a momentary contact switch. After 10 seconds (exact time
isn't critical here +, - a second or two is fine) the circuit momentarily
outputs a pulse. I thought I'd feed the pulse into a switching transistor to
make it operate as a momentary contact switch.

Lawrence

C

Charles Jean

Jan 1, 1970
0
I'm looking to set us a simple way to turn something on after 10 seconds. The
resulting output after the end of the 10 seconds needs to be a momentary pulse
and not stay in a closed position.

-----------------------------------------------------------------------^-

Like this.

Circuit is started with a momentary contact switch. After 10 seconds (exact time
isn't critical here +, - a second or two is fine) the circuit momentarily
outputs a pulse. I thought I'd feed the pulse into a switching transistor to
make it operate as a momentary contact switch.

Lawrence
___

Here's one that gives about 1 second delay, 1 second pulse. Could
also use one 556 instead of 2 555s. Delay/pulse is 1.1RC where R is
the 22K resistors and C is the 47 uF capacitors.
"Sic hoc legere scis nimium eruditionis habes."
(If you can read this, you're overeducated.)

T

Terry Pinnell

Jan 1, 1970
0
Tristar said:
I'm looking to set us a simple way to turn something on after 10 seconds. The
resulting output after the end of the 10 seconds needs to be a momentary pulse
and not stay in a closed position.

-----------------------------------------------------------------------^-

Like this.

Circuit is started with a momentary contact switch. After 10 seconds (exact time
isn't critical here +, - a second or two is fine) the circuit momentarily
outputs a pulse. I thought I'd feed the pulse into a switching transistor to
make it operate as a momentary contact switch.

Lawrence

This does what I think you want:
http://www.terrypin.dial.pipex.com/Images/10sMono+Pulse.gif

T

Tristar

Jan 1, 1970
0
This looks easy Terry, I tried Johns circuit on a breadboard last night. I'll
give this a try too.

Thanks, Lawrence

BTW, nice website you have there.

J

Jasen Betts

Jan 1, 1970
0
I'm looking to set us a simple way to turn something on after 10 seconds. The
resulting output after the end of the 10 seconds needs to be a momentary pulse
and not stay in a closed position.

-----------------------------------------------------------------------^-

Like this.

set up the 555 as a monostable and use a capicitor in series with the output
to pulse the transistor's base when the output changes state after the 10
seconds have elapsed. (there'll bve a pulse to the transistor when it starts
too but it'll be the wrong polarity and the transistor will ignore it)

T

Terry Pinnell

Jan 1, 1970
0
Jasen Betts said:
set up the 555 as a monostable and use a capicitor in series with the output
to pulse the transistor's base when the output changes state after the 10
seconds have elapsed. (there'll bve a pulse to the transistor when it starts
too but it'll be the wrong polarity and the transistor will ignore it)

That's what my circuit does.

T

Tristar

Jan 1, 1970
0
Hi Terry, It's probably me but I couldn't get it to work, I used a pnp 2N3906.
I tried various combinations of caps and resistors but no luck.

Any ideas?

In

T

Terry Pinnell

Jan 1, 1970
0
Tristar said:
Hi Terry, It's probably me but I couldn't get it to work, I used a pnp 2N3906.
I tried various combinations of caps and resistors but no luck.

Any ideas?

In

made a wiring error. As you see from the simulation - the circuit does
what it's supposed to do.

How are you testing it? 'Scope, DMM...?

Is the mono working? If not, then obviously the brief pulse won't be
generated.

T

Tristar

Jan 1, 1970
0
Hi Terry, I gave it another try and Success this time!

Thanks again,

Lawrence

T

Terry Pinnell

Jan 1, 1970
0
Tristar said:
Hi Terry, I gave it another try and Success this time!

Thanks again,

Lawrence

Good - thanks for letting us know.

BTW, *bottom* posting is the favoured standard here.

SARAH

Oct 19, 2010
1
Dear Mr. Terry,

Kindly precise the transistor used in your circuit, as I tried BC556, and the result was not a pulse, It is remaining high.

Actually I am trying to have a delayed 3 seconds pulse with 1 second width.

Best Regards,

Sarah

Replies
7
Views
1K
Replies
5
Views
677
Replies
48
Views
4K
Replies
21
Views
3K
Replies
29
Views
3K