# intermitant switch?



## Sickie Ickie (Jun 20, 2006)

Okay, all you tech gurus,

I have a doll that says things when a button is pushed. I was thinking of running a PIR to the button wires, but I came up with a different thought.

What is a quick circuit I can make to contact the button wires on and off at a timed interval?

And how much would cost be?

I'll be honest and say I don't know if I'll use it, but I'd like for the option to be there.


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## The_Caretaker (Mar 6, 2007)

A simple 555 timer circuit would work


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## Otaku (Dec 3, 2004)

The_Caretaker said:


> A simple 555 timer circuit would work


Sure would. Easy and cheap.


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## groovie ghoulie (Nov 12, 2008)

The_Caretaker said:


> A simple 555 timer circuit would work


And what praytell would that circuit look like?


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## joker (Sep 25, 2007)

groovie ghoulie said:


> And what praytell would that circuit look like?


Like this


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## Otaku (Dec 3, 2004)

SI,
Here's a link to very good site for 555 circuits.

http://home.cogeco.ca/~rpaisley4/LM555.html

Scroll down to the "Basic Astable Oscillator Circuit". Connect a relay to Pin 3 and ground and that's your switch.


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## Sickie Ickie (Jun 20, 2006)

er...there is no "Basic Astable Oscillator Circuit". ???


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## Jaybo (Mar 2, 2009)

http://home.cogeco.ca/~rpaisley4/LM555.html#4


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## Sickie Ickie (Jun 20, 2006)

terrific guys! Thanks! 

So, for a 1 minute interval I'd need 100uf cap, and for 30 sec interval I'd need a 50uf cap if I'm figuring it out correctly.

The diagram shows four leads. Two on the left, two on the right. I'm confused about these. Can anyone here tell me what these leads hook to?


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## Otaku (Dec 3, 2004)

The two on the left are the power source and ground, the two on the right are the ground and the output from Pin 3 of the 555 IC. For your application, you'd want to build the astable circuit that allows control of both the high and low (on and off) times. I have a variant that has a fixed time for the "on" time and can vary the "off" time. I have the schematic on my work computer, but I'll be out of town for a few days. I can post it when I get back next week.


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## Sickie Ickie (Jun 20, 2006)

power source and ground? This is to turn a motor on or off then. hmmmm would it work for a button switch then since there's no power source going into it? (two wires only) *scratches head*


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## Otaku (Dec 3, 2004)

The 555 chip requires power (5-15VDC) to operate, of course, and the output from Pin 3 is a portion of that power. There's typically a 1-2 volt drop across the chip. The output voltage from Pin 3 and the circuit ground get connected to a relay, which will activate the doll. The wires going to her button attach to the Common and Normally Open pins on the relay. When the timer goes "high" voltage goes to the relay, closing the contacts and making her speak. Your timing cycle would be set up to have a fixed "on" time of ~1 sec and an adjustable "off" time.


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## Sickie Ickie (Jun 20, 2006)

ah! I get it. Does radio shack have a 555 timer? I have one near me for convenience.


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## Otaku (Dec 3, 2004)

Sickie Ickie said:


> ah! I get it. Does radio shack have a 555 timer? I have one near me for convenience.


Yes, but they mostly sell the 555CN, the CMOS version. It behaves the same as the LM555 but is much more sensitive to static charges and power supply spikes. I'd recommend using a 9 volt battery to power the board and a 5VDC relay. I think you can get everything you'll need to build this from RS, but it'll be more expensive than All Electronics - and they sell the LM555 chip, too. There's more to it than just the 555 - capacitors, resistors, potentiometers, a PCB etc. I can help you out after I get back in town this weekend.


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## Sickie Ickie (Jun 20, 2006)

I must have missed the pent. I'll wait for this weekend, then.


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## Otaku (Dec 3, 2004)

groovie ghoulie said:


> And what praytell would that circuit look like?


Here's what I whomped up for SI:

http://halloweengallery.com/displayimage.php?pos=-3855

For some reason I couldn't upload the GIF to this post.


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## Sickie Ickie (Jun 20, 2006)

I'm looking forward to trying it this week!


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## DarkLore (Jan 25, 2009)

Keep us posted...I want pics.


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## bradbaum (Jul 26, 2008)

Sounds like you are on your way with the 555 circuit.

Here is another circuit, I built a few of these and used them to drive my boss nuts when I was young and stupid.

http://www.redcircuits.com/Page111.htm

The circuit turns on in the dark, and chirps intermittently. The ripple counter changes the amount of time between each chirp.

It could be modified to fire a relay instead of the speaker.


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## Otaku (Dec 3, 2004)

That must have been fun, Brad. I was talking to a guy at work last week about circuits and he mentioned that he hacked the chirp circuits that are in smoke detectors. It's what you hear when the battery gets low, or the detector loses it's line voltage. I'm sure that this circuit is more realistic, though. Thanks - I'll add this to the library!


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## groovie ghoulie (Nov 12, 2008)

Otaku said:


> Here's what I whomped up for SI:
> 
> http://halloweengallery.com/displayimage.php?pos=-3855
> 
> For some reason I couldn't upload the GIF to this post.


Thank You, once again Otaku! It's so nice to have a Electroics Guru as our friend!!


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## Dr Morbius (Sep 21, 2004)

bradbaum said:


> Sounds like you are on your way with the 555 circuit.
> 
> Here is another circuit, I built a few of these and used them to drive my boss nuts when I was young and stupid.
> 
> ...


Young, but stupid? That's something I would do tomorrow to my boss if I could, and I'm not young..maybe I am stupid? LOL! I'm always up for good practical joke, and this sounds like a winner.


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