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NE555 versus TLC555 ??

Discussion in 'Electronic Basics' started by Dave, I can't do that, Aug 3, 2008.

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  1. Hi,

    I have a circuit that calls for TLC555 and I have about a zillion

    Why couldn't I use the NE in place of the CMOS version?


  2. Bob Monsen

    Bob Monsen Guest

    You can use them! Why not?

    The differences are:

    1) they probably don't have 'rail-to-rail' outputs
    2) they use about 100 times as much power
    3) they require lots more current to trigger
    4) they have a slightly lower Vmax
    5) NE555 will drive more current on the output

    Bob Monsen
  3. Jamie

    Jamie Guest

    I don't know why? Maybe you need lower voltage rating
    part? supply (I) lower? Closer to the rails, higher freq maybe? If
    those aren't a problem then use
    the NE version."
  4. neon


    Oct 21, 2006
    Monsen Give The Answer Usu It.
  5. On Aug 4, 6:00 am, (Bob Masta) wrote:

    Thanks Bob and everyone else who replied. OK, so no breaking news here
    about me being a newbie. <grin> I didn't think the circuit would have
    much bearing on the case other than lower power needed by the CMOS

    I didn't bother with a link to the circuit since low power is not an
    issue with my application.

    However I do need an operating frequency of 5KHz and 1-uS pulse width
    at the lowest setting.

    Here's the schematic...


  6. You can get around the limited output voltage swing by adding a 1k resistor
    from pin 3 to +5V. Also, the supply voltage needs to be bypassed near the
    IC with a small 100nF or so capacitor in addition to the 100 uF shown. And
    a similar bypass capacitor from pin 5 to GND is recommended for control
    voltage stability, and you can add a resistor to GND to lower the threshold
    and trigger to work better with the reduced output swing.

    An even better circuit for motor control is the H-bridge, an example of
    which is referenced in a link on the website you listed:

    I have a DC motor control demo board from Microchip that uses an H-bridge
    with PWM to accomplish forward and reverse motor operation and dynamic
    braking (which the 555 circuit does not have). It uses four MOSFETs and a
    PIC16F684, and can even be controlled via a PC serial port and a simple
    Windows GUI:

    Good luck,

  7. Thanks again to everyone who has contributed but you guys are starting
    to get way out of my knowledge-depth.

    I think I will order some CMOS, I only asked as I don't have any on
    hand but I have plenty of NE555.

  8. The NE555 should be fine to get started and learn, especially if you add
    the pullup on the output. The CMOS versions are not expensive, but you'll
    probably pay a lot for shipping, unless you bundle them with other items
    you need. You can also try getting samples from TI, Linear, Microchip,
    Maxim, or whoever has what you would like to try. You can pretend that you
    are a company. Who knows, you might really get into this and start one. I
    have had my own S Corporation consisting of only myself for almost 20

    I only suggested the Microchip parts because PICs and similar uPs are often
    the best way to accomplish what was once only possible with discrete parts.
    It is much more convenient to design a basic circuit (or use a pre-made
    demo board), and then change frequency, pulse width, and other parameters
    just by programming or by sampling the voltage on a pot. And once you learn
    some basic PIC programming, it opens up a lot of opportunities.

    But you do need to get a good grasp of basic fundamentals as well. And
    balance the fun and the mental parts!

  9. Dave

    Dave Guest

    Hi Paul,

    Thanks, I too have an S-Corp and a garage full of metalworking machines,
    some with CNC but I am pretty much a newbie with electronics.

    Over the years, I have made many kits and have programmed PCs for many
    years but never quite got into the uP field.

    Might be time to take a closer look. I like the idea of being able to
    change frequency and duty cycle without soldering parts.

    I am using an account with to weed out the
    bullshit and spam. If you are responding from within Google Groups I
    will not see your reply. Try usenet4all I think you will like it. It is
    Usenet the way it used to be. Yes, I am THAT old! <grin>
  10. Jasen Betts

    Jasen Betts Guest

    There are many points of difference between the two.
    there is certasinly a chance that the NE is suitable.

    some points to consider

    operating voltage
    output current
    power consumption

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