555 used as a delayed pulse generator?

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.

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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

Reply to
Tristar
Loading thread data ...

time

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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.)

Reply to
Charles Jean

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Reply to
Charles Jean

time

This does what I think you want:

formatting link

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Terry Pinnell
Hobbyist, West Sussex, UK
Reply to
Terry Pinnell

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.

pulse

time

Reply to
Tristar

pulse

That's what my circuit does.

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Terry Pinnell
Hobbyist, West Sussex, UK
Reply to
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

Reply to
Tristar

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.

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Terry Pinnell
Hobbyist, West Sussex, UK
Reply to
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)

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Bye.
   Jasen
Reply to
Jasen Betts

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

Thanks again,

Lawrence

2N3906.
Reply to
Tristar

Good - thanks for letting us know.

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

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Terry Pinnell
Hobbyist, West Sussex, UK
Reply to
Terry Pinnell

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