experience with 555 timer

Discussion in 'General Electronics Chat' started by clintonb, Mar 16, 2015.

  1. clintonb

    Thread Starter Active Member

    Mar 6, 2011
    42
    0
    I've been trying to drive a piezo element that according to the manufacturer runs at 1.6mHz.

    The best chance I have is a 555 timer that claims to be suitable up to 2mhz. I understand the maths and I've done the calcs and it should technically work with 300ohm 300 ohm and 10pf capacitor. I ran the circuit in circuit wizard and I get a square waveworm that looks to go crazy but it doesn't give me a way of actually measuring the frequency accurately.

    Can anyone offer any experience as to what limits are imposed on the user? To increase the frequency for example you can use a smaller capacitor that charges to the threshhold faster or a smaller resistor to charge the capacitor faster. Is there an absolute minimum capacitor that is allowed and any further changes would need to be done using resistors etc?
     
  2. MCU88

    Member

    Mar 12, 2015
    360
    35
    Wha
    What ARE YOU making?
     
  3. clintonb

    Thread Starter Active Member

    Mar 6, 2011
    42
    0
    It
     
  4. clintonb

    Thread Starter Active Member

    Mar 6, 2011
    42
    0
    Its just a square wave generator that sends its signal into a mosfet that switches the piezo transducer to produce a humidifier.
     
  5. Gibson486

    Member

    Jul 20, 2012
    199
    12
    I am confused. You just need a way to measure the frequency? Why not just build it and measure it with a scope? For waveform generation, all the players left the market. I think the 555 may be the only true timer IC left. With the advent of DDS chips (you will have to adjust voltage level externally) and microntrollers (hint....microcontrollers can do this very well provided you do not use Arduino), the need for the timer ICs is becoming small since they "only" go up to 2 Mhz.
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
  7. wayneh

    Expert

    Sep 9, 2010
    12,093
    3,033
    I know that humidifiers are "ultrasonic" but what you are describing is a radio frequency far above anything "sonic". I didn't think you needed to go that high?
     
  8. clintonb

    Thread Starter Active Member

    Mar 6, 2011
    42
    0
    I'm looking
    I didn't either. Some sources suggest that 500khz should be enough whereas other suggest that 2 mhz is required. I'm using a plain atmega32 and I'm going to try generate the signal as suggested above. I want to test different values and check it out for myself.
     
  9. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,518
    1,247
    cmartinez likes this.
  10. wayneh

    Expert

    Sep 9, 2010
    12,093
    3,033
    What little reading I did confirms that 1.7MHz is typical, depending on the transducer. News to me, but me learning something is not news.
     
    cmartinez likes this.
  11. cmartinez

    AAC Fanatic!

    Jan 17, 2007
    3,555
    2,519
    Why don't you just use a programmable crystal oscillator? It should be much easier to use, and easier to experiment with for your circuit. Plus, they've got a much broader frequency range than even the most advanced 555's. And once you find the right frequency that you need, you can later design a simpler circuit with cheaper parts knowing exactly what you want.
     
Loading...