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Sine to square wave converter

Discussion in 'Electronic Basics' started by Jack// ani, Mar 24, 2005.

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  1. Jack// ani

    Jack// ani Guest

    Hi all,

    How can I convert 50Hz AC to a square wave so that I can feed it to a
    microcontroller? Will CD4093 work here? I will steps down the ac to
    5volts then use a diode in series before hooking it to CD4093?

  2. Lord Garth

    Lord Garth Guest

    This will explain how you should proceed:
  3. Jack// ani

    Jack// ani Guest

    Thanks for reply Lord. Unfortunately link is dead!
  4. Lord Garth

    Lord Garth Guest

    Not from here though it is slow....send an email address or I can post
    it to alt.binaries.schematics.electronic
  5. Jack// ani

    Jack// ani Guest

    Whoops, i'm sorry the link is working! Something was wrong here!
  6. I read in that Jack// ani
    IE6 barfs badly, but Firefox retrieves it OK. I'm having the same
    problem with PDFs from other sites, using IE 6 and Acrobat 6.
  7. There are trivial ways to do all depends on how "square" square must
    be. Do you absolutely HAVE to have 50.000% duty cycle, or are you only
    worried about using it as a leading (or falling) edge clock. Do you have
    any spare circuits in another multi-circuit chip, or do you have room for a
    dedicated chip. Tell us what matters to you and we'll have a shot at making
    the sucker go.

  8. Guest

    If a 50% duty cycle is important, a zero-cross detector into a D
    flip-flop as divide by 2 would get pretty close.
  9. Pooh Bear

    Pooh Bear Guest

    Works fine for me.

  10. One simple way is to use a large value resistor, like 1MEG, into the
    base of an NPN transistor. The emitter should be grounded, and the
    collector tied to your +5V power supply rail through a 100k resistor.
    Take the output from the collector of the transistor. Note that for this
    to work, your power supply should have it's ground someplace near earth

    One problem with this is that the base goes very negative. This can be a
    problem. Thus, if you use a diode from ground to base, if the input goes
    very negative (which it will, of course) the diode will keep it within
    about 7/10 of a volt of the ground.


    | | 100k
    | |
    o------ PIC Input
    1MEG |
    ___ |/
    AC IN -|___|----o----|
    | |>
    | |
    - |
    ^ |
    | |
    | |
    GND ------------o------'
    (must be near neutral)
    (created by AACircuit v1.28.5 beta 02/06/05

    This is probably going to be fast enough so that the PIC will only see
    one transition for each transition of the AC line. However, if it isn't,
    you can build a simple schmitt trigger out of two transistor that will
    prevent false triggering.

    That would be like this (which is swiped out of Art of Electronics,
    Volume 2)

    .--------------o--------- VCC
    | |
    .-. .-.
    | | 1.5k | |1k
    | | | |
    '-' '-'
    | ___ |
    o---|___|--. o------Output to PIC
    | 10k | |
    1MEG | | |
    ___ |/ | |/
    AC IN -|___|----o----| '-|
    | |> |>
    | | |
    - '------o-------'
    ^ |
    | 100R |
    | ___ |
    GND ------------o----|___|----'
    (must be near neutral)

    (created by AACircuit v1.28.5 beta 02/06/05

    However, I think the first circuit is probably ok.

    Robert Monsen

    "Your Highness, I have no need of this hypothesis."
    - Pierre Laplace (1749-1827), to Napoleon,
    on why his works on celestial mechanics make no mention of God.
  11. mike

    mike Guest

    All depends on what you're trying to do.
    If all you need is line synchronization...
    On PIC16F877A, I've used a voltage divider directly into the input.
    The inputs are clamped. As long as you have enough series resistance to
    limit the current, it should work ok. External clamps are even safer.
    Transistor is better. You can spend as much as you like.
    Use SW to mitigate noise.
    Assume you have mains isolation.

    Return address is VALID but some sites block emails
    with links. Delete this sig when replying.
    Wanted, PCMCIA SCSI Card for HP m820 CDRW.
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  12. Fred Bloggs

    Fred Bloggs Guest

    It depends on what powers your logic circuit and what it needs the 50Hz
    square wave for. You can't just couple a voltage off the line into a GND
    referenced circuit and expect it to work trouble free. Also, most
    circuits are looking for zero-crossing on the AC- waveform and this is
    difficult to get with the massive attenuation required of a line voltage
    in conjunction with the fairly large uncertainties of typical Schmitt
    trigger thresholds and hysteresis. You will get a square wave, but it
    may not be of much use.
  13. John Fields

    John Fields Guest

  14. Agreed. I could probably have made a movie of it in the time it would
    take a PIC-er to just get started! Here it is:
  15. marika

    marika Guest

    thanks for this great freakin link!!!!


    "...aside from Anyone know any good ones?
    While uknova is a good site for certain shows, I find that you usually
    get zero response to requests for stuff not already torrented. The
    fact that the mods don't allow you to bump your requests on the forum
    doesn't help either, as the volume of traffic means that your post
    soon drops off the page... "-- a single locust
  16. Bob Monsen

    Bob Monsen Guest

    This took 5 minutes to code (adapted another project). 15 if you include
    the setup, programming, testing, and bugfix (I inadvertently forgot to
    call init(), and it didn't work the first time). Only one chip, a pot, 5
    resistors, and 4 leds. Sadly, I don't have a movie camera, or I would
    record it. This is compiled with the free 'hitech lite' C compiler, and is
    downloaded to a pickit 1 using lawlor's usb_pickit for linux.

    The PIC12F675 is an 8 pin uC, which supports ADC, timer interrupts, and
    such. Pin 7 is used as the ADC input, so changing the voltage changes the
    rate of change of the display, from once every 2 seconds to as fast as it
    can go. The period is about Vin/Vcc * 2048 for Vin > 0.

    Pin 6, 5, 3, and 2 are A, B, C, and D. Pin 4 is the reset, pin 1 is Vcc,
    and pin 8 is GND. A-D can source up to 20mA, so a 1k resistor between it
    and the LED limits current to about 3.5mA.

    (for the curious, it uses a 1ms interrupt to do delays. The result of
    the high byte of the AD is between 0 and 255. Thus 8 * AD is from 0 to
    2040, and just delaying that number of ms interrupts provides the ability
    to change the period from fast to slow)

    BTW, I'm sure we all appreciate JF's and Terry's efforts to help people
    out. I wish everybody's posted circuits were as well thought out, tested,
    and nicely presented as the ones they post.


    #include <pic.h>


    unsigned int g_ticks; /* Ticks since startup */

    #define TICKS_PER_SECOND 1000

    #define LED_A GPIO1
    #define LED_B GPIO2
    #define LED_C GPIO4
    #define LED_D GPIO5

    void init_gpio(void)
    GPIO = 0;

    void init_tmr0(void)
    /* prescaler is 1:4, GPIO pullups are disabled */
    OPTION = 0x81;

    void init_tmr1(void)
    T1CON = 0; /* Disabled */

    void init_comparator(void)
    CMCON = 0x7; /* Turn off the comparator */
    VRCON = 0x0;

    void init_a2d(void)
    ANSEL = 0x11; /* Fosc/8 and RA0 is analog */
    ADCON0=0x00; // Left justify output
    ADON=1; // turn on the A2D conversion module

    void init_ee()

    void init_interrupts(void)
    INTCON = 0xA0;

    void init(void)

    TRISIO = 0x01; /* RA0 is ad input, rest are outputs */


    unsigned int get_voltage (void)
    GODONE=1; /* initiate conversion */

    while(GODONE) /* wait for result */

    return ADRESH;

    void wait_ms(unsigned int x)
    unsigned int temp = g_ticks + x;
    while (temp != g_ticks);

    void main(void)
    int state = 0;


    LED_A = 1;
    LED_B = 1;
    LED_C = 0;
    LED_D = 0;

    for (;;)
    unsigned int ms_to_wait = get_voltage() * 8;

    case 0:
    LED_A = 0;
    LED_C = 1;

    case 1:
    LED_B = 0;
    LED_D = 1;

    case 2:
    LED_C = 0;
    LED_A = 1;

    case 3:
    LED_D = 0;
    LED_B = 1;
    state = 0;

    static void interrupt isr(void)
    T0IF = 0;
    TMR0 = 6;

  17. Jasen Betts

    Jasen Betts Guest

  18. Cliff

    Cliff Guest

    On Mon, 28 Nov 2005 14:51:55 -0600, John Field
    You think that resistivity controls the speed of light
    I think I heard that a good vacuum has a lot of resistanc
    but a fairly high speed of light
    The speed of light goes down as things become more
  19. Fred Abse

    Fred Abse Guest

    On Tue, 29 Nov 2005 07:31:11 +0000, Jasen Betts wrote
    Most are :-
    Run the LTSpice simulation below, three cases of 1000 miles of RG59-U
    terminated. shorted, and open at 1 MHz. You'll find all 3 cases loo
    75 ohms. Constants are per Belden data

    LTSpice is free, if you didn't already know that, and runs under WINE
    (well at least here it does.

    SHEET 1 880 68
    WIRE -128 144 -128 3
    WIRE -128 160 -128 14
    WIRE -128 320 -128 24
    WIRE 48 320 -128 32
    WIRE 48 320 48 6
    WIRE 80 320 48 32
    WIRE 80 320 80 17
    WIRE 112 32 -128 3
    WIRE 112 64 48 6
    WIRE 112 144 -128 14
    WIRE 112 176 80 17
    WIRE 128 320 80 32
    WIRE 128 352 128 32
    WIRE 240 176 208 17
    WIRE 240 320 128 32
    WIRE 240 320 240 17
    WIRE 288 64 208 6
    WIRE 288 320 240 32
    WIRE 288 320 288 6
    WIRE 384 32 208 3
    WIRE 384 144 208 14
    WIRE 384 320 288 32
    WIRE 384 320 384 22
    FLAG 128 352
    SYMBOL ltline 160 160 R
    SYMATTR InstName O
    SYMATTR Value RG59
    SYMBOL voltage -128 144 R
    WINDOW 123 0 0 Left
    WINDOW 39 0 0 Left
    SYMATTR InstName V
    SYMATTR Value SINE(0 1 1e6
    SYMBOL res 368 240 M18
    WINDOW 0 36 76 Left
    WINDOW 3 36 40 Left
    SYMATTR InstName R
    SYMATTR Value 7
    SYMBOL ltline 160 48 R
    SYMATTR InstName O
    SYMATTR Value RG59
    TEXT -152 456 Left 0 !.model RG59U LTRA(len=5.28e6 R=51.6e-3 L=0.115
    TEXT -162 506 Left 0 !.tran 0 1m 0 1
    TEXT 496 456 Left 0 ;(Belden 8263

    [Transient Analysis

    Active Pane:

    traces: 1 {524290,0,"v(n001)/Ia(O1)"
    X: ('u',0,0,8e-005,0.0008
    Y[0]: (' ',0,0,10,100
    Y[1]: ('_',0,1e+308,0,-1e+308
    Units: "Ohm" (' ',0,0,0,0,10,100
    Log: 0 0

    traces: 1 {524291,0,"v(n001)/Ia(O2)"
    X: ('u',0,0,8e-005,0.0008
    Y[0]: (' ',0,0,10,100
    Y[1]: ('_',0,1e+308,0,-1e+308
    Units: "Ohm" (' ',0,0,0,0,10,100
    Log: 0 0

    traces: 1 {524292,0,"v(n001)/Ia(O3)"
    X: ('u',0,0,8e-005,0.0008
    Y[0]: (' ',0,0,10,100
    Y[1]: ('_',0,1e+308,0,-1e+308
    Units: "Ohm" (' ',0,0,0,0,10,100
    Log: 0 0
  20. Terry Given

    Terry Given Guest

    NunYa Bidness wrote
    thats not correct. case in point, it is quite feasible to analyze a
    conductor as comprising an n-tuple of (very thin) strands, completely
    ignoring strand-to-strand conduction (if the strands are thin enough)
    once hacked up a Mathcad worksheet that did exactly that, and i
    well with messrs Vandelac & Ziogas. slow though :

    if your argument were correct, multiple parallel strands of magne
    in a xfmr would behave just like litz, and it doesnt

    A friend also had a problem a few years back with a litz cable, abou
    OD, with many thousands of strands. the strands were woven int
    bundles, IIRC about 5mm OD, and these were then woven into the larger
    cable. A screw-up by the manufacturer meant the centre two bundle
    not woven at all, but ran down the center of the cable. When they
    started pumping a few hundred kW into the cable, losses were extremel

    high. Close inspection of a cable segment showed why, and severing th

    central bundles solved the problem
    the bundle doesnt do the pushing, its the H field

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