555 used as a delayed pulse generator?

[Tristar]

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.


Thanks in advance!

Lawrence

 

[Charles Jean]

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.


Thanks in advance!

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.)

 

[Terry Pinnell]

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.


Thanks in advance!

Lawrence

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

 

[Tristar]

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.

 

[Jasen Betts]

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)

 

[Terry Pinnell]

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.

 

[Tristar]

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

 

[Terry Pinnell]

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

Without more information, not really. Best guess would be that you've
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.

 

[Tristar]

Hi Terry, I gave it another try and Success this time!

Thanks again,

Lawrence

 

[Terry Pinnell]

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]

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