Pseudo random pulse generator

Discussion in 'General Electronics Chat' started by rjjenkins, Apr 17, 2011.

  1. rjjenkins

    Thread Starter Member

    Apr 16, 2011
    102
    2
    Hello
    I'd like to build something that generates pulses at seemingly random time intervals, ranging from about 0.5s up to about 5s. The pulses themselves need to be about 1s long. It doesn't really have to be at all random, it just has to look random to the casual observer. And I'd like to do it with as few components as possible. Your thoughts welcome.
     
  2. hexreader

    Active Member

    Apr 16, 2011
    250
    82
    Then the obvious way is to use a (8 pin?) microcontroller (e.g. PIC, ATMEL), a 0.1uF decoupling capacitor and a battery.

    3 components.

    On the down side: you will need a PIC or ATMEL programmer connected to a PC and some programming knowledge.

    Mind you - there is Arduino and PICaxe, which do not require a programmer, but still require connecting to serial port and learning some programming.
     
  3. rjjenkins

    Thread Starter Member

    Apr 16, 2011
    102
    2
    Thanks; I think I'd better specify some more what I'm after!
    This is for a magic trick, and the components have to fit into as small a space as possible, so that they can be easily concealed. It all has to be self-contained and running off a very small battery. I'm wondering whether it would be possible to have two oscillators running at different speeds but somehow interfering with each other to produce something that looks a bit random.
     
  4. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
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    I don't think you will find a smaller circuit configuration and lower current than an 8-pin microcontroller, especially if you go with a surface mount package. One import, missing spec...what does the random pulse out do?...what is it connected to?

    Ken
     
  5. rjjenkins

    Thread Starter Member

    Apr 16, 2011
    102
    2
    It goes to a "muscle wire" - one that contracts when a current flows through it. I presume it would be easy enough to add in a transistor switch if necessary.
    [the wire is sewn invisibly into a handkerchief - as it contracts it gives the impression of the handkerchief twitching as if "haunted". I am imagining the circuitry also sewn in, in a corner that can be held in the hand until the handkerchief is folded over. This is a classic magic effect, done without the electronics]


     
  6. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    http://www.testingtesting.org/?p=1230 It can take quite a bit of current to move the wire a little bit. A 3v lithium coin battery might have enough energy to power a microcontroller, and periodically move the wire. It would take some real world experimenting.

    Ken
     
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