Sine to square wave converter

Thanks for reply Lord. Unfortunately link is dead!

Whoops, i'm sorry the link is working! Something was wrong here!

There are trivial ways to do it...it 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.

Jim

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

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 ground.

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.

So

VCC | .-. | | 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.

--
Regards,
   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.

This will explain how you should proceed:

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

I read in sci.electronics.design that Jack// ani wrote (in ) about 'Sine to square wave converter', on Thu, 24 Mar 2005:

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.

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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. mike

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Works fine for me.

Graham

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.

thanks for this great freakin link!!!!

mk5000

"...aside from uknova.com. 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

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Thanks! :-)

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:

--
Terry Pinnell
Hobbyist, West Sussex, UK

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.

Regards

--------------------------------------------------------------------------- #include

__CONFIG(UNPROTECT & BORDIS & MCLREN & PWRTDIS & WDTDIS & INTIO);

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) { OSCCAL = _READ_OSCCAL_DATA();

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

init_gpio(); init_tmr0(); init_tmr1(); init_comparator(); init_a2d(); init_interrupts(); }

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

while(GODONE) /* wait for result */ { continue; }

return ADRESH; }

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

void main(void) { int state = 0;

init();

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

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

wait_ms(ms_to_wait); switch(state) { case 0: LED_A = 0; LED_C = 1; state++; break;

case 1: LED_B = 0; LED_D = 1; state++; break;

case 2: LED_C = 0; LED_A = 1; state++; break;

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

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

g_ticks++; }

What program lang did you use It looks like C to me or is it Basic?

Eric

It is C. There is a free compiler available from

which works for pic 12 and 16 series chips.

--

Bye.
   Jasen

Characteristic impedance is purely a function of the

inductance distributed along the line's length, and

dielectric were perfect (infinite parallel

superconducting (zero series resistance).

value relating a transmission line's

in a vacuum. Values range

coaxial cables.

square

odd then that the speed of propagation in conductors

Since resistivity varies between conductors because of

they're composed and inductance varies

one _not_ expect c to vary?

You think that resistivity controls the speed of light? I think I heard that a good vacuum has a lot of resistance but a fairly high speed of light. The speed of light goes down as things become more

conductive?

--
Cliff