What component lets current flow for (e.g.) 1 millisecond?

Discussion in 'General Electronics Chat' started by DUT99, Mar 13, 2012.

  1. DUT99

    Thread Starter New Member

    Mar 13, 2012
    I'm kind of a newbie to electronics, and I need a component that lets current flow for a very short amount of time, e.g. 300 microSeconds or 2 milliSeconds.

    Does anyone know what kind of component I'm looking for?

    Maybe it's called relay or switch? (But there seems to be many types)

    To clarify: I want to press a button that lets the short pulse go through my circuit. There should only be one pulse for each time I press the button.

    Unfortunately I'm not quick enough to press it for 1 millisecond :)

    I don't know exactly how long the pulse should be in time, I will have to test. Hopefully I can find a component that lets me vary the length of time.

    I will connect the component to some capacitators to adjust the voltage of my pulse.

    Thanks in advance!
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
    What is your circuit?

    Please provide more details, like what is the load, how much current is needed, what's the power supply voltage?

    You can generate the pulse with a monostable 555. Learn about it here or do a search on AAC or the internet, there are inumerous examples available.
  3. DUT99

    Thread Starter New Member

    Mar 13, 2012
    Thanks for the reply!

    I don't know the load. I will experiment with the voltage until I get the current I want. Perhaps voltage will be high, over 100 V.

    Thanks for the link, but it seems like a lot of work. And the text says: "If you force the timer input to stay low past timeout the output will stay high, even though the timer has finished. As soon as this ground is removed the timer will go low."

    If I understand this correctly I would have to release the switch within the time of the pulse. If I want my pulse to be 2 milliSecond or even 300 microSecond, that will of course be impossible. I don't have that fast fingers... :)

    What is AAC? Advanced Audio Coding? Agility Association of Canada? Antimicrobial Agents and Chemotherapy? :) Those are some of the hits on Google ... lol

    Again, thanks for replying!
  4. DerStrom8

    Well-Known Member

    Feb 20, 2011
    DUT99, you're on AAC! :D

    AllAboutCircuits. And you're correct--in order for a monostable 555 to output a pulse of 1ms, the input pulse would have to be shorter than that. Otherwise the timer will stay on. Really, this is probably a job for a microcontroller, since most other chips won't do this for you. Do you have any experience with programming?

    Der Strom
    Last edited: Mar 14, 2012
  5. praondevou

    AAC Fanatic!

    Jul 9, 2011
    You can trigger the 555 with a pulse shorter than the output pulse by capacitively coupling the input pulse. It's not complicated at all.
  6. MrChips


    Oct 2, 2009
    You can use a monostable multivibrator such as a 74121 or 74123 (74LS123) or 4528/4538 (MC14538) to generate a pulse of a given length, independent of how long you hold down the button.