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Another 555 question

Discussion in 'Beginner Electronics' started by Henry, Dec 27, 2005.

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  1. Henry

    Henry Guest

    Looking for a way to make a 555 timer astable circuit "triggerable." Seem
    all the circuits I see (I think the some one over and over again) show an
    astable 555 rigger to run constantly as a "clock." Right now I am using a
    transistor to power up and down the 555, but it seems there should be a
    better way. Basically I want "bursts" of pulses based on a trigger. (And it
    needs to reset itself, not needing any manual reset.)

  2. Henry

    Henry Guest

    Thanks every one. Okay, this seems to work so far. I have connected the 555
    Reset connection to ground with a 10K pull-down resistor. Then I pull the
    Reset up with a NPN transistor connected to Vcc (+5v) when I want it to
    trigger (vibrate?). Anyway, seems to work so far. I tried a higher pull-down
    (100K) resistor, but there was some auto-triggering and mis-fires. Is 10K
    good enough for a pull-down in this case or should I get some 20K or 50K?

  3. Henry

    Henry Guest

    Because it took an extra 555 timer, if I understood it correctely. I only
    have a couple of these and it seemed a waste to use a timer chip where a
    single transistor and resistor (of which I have many) seem to do the same.
    Otherwise I have used your advise in other questions. No insult intended.
    But I am also tinkering and experimenting and I may not be completely
    explainisg myself when I ask some of these questions. I need my last 555
    timer as reset timer for something else. I have also read that 555 timers
    tend to consume power and not sure how many parts I can drive from 4-AAs. Im
    already using about 7 TTL logic chips, a 555 timer, (maybe another soon to
    complete the auto reset part) about 6 LEDs, and 8-10 transistors. Im already
    doing things like combining 2 NAND gates to make a single AND gate. Im
    improvising with what I have.

  4. Once again I'm not sure what you want, but I've gated 2 555s together with
    different pulse rates to achieve something similar to what you describe.
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