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Sine to square wave converter

J

Jack// ani

Jan 1, 1970
0
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?

Thanks
 
J

Jack// ani

Jan 1, 1970
0
Thanks for reply Lord. Unfortunately link is dead!
 
L

Lord Garth

Jan 1, 1970
0
Jack// ani said:
Thanks for reply Lord. Unfortunately link is dead!
Not from here though it is slow....send an email address or I can post
it to alt.binaries.schematics.electronic
 
J

Jack// ani

Jan 1, 1970
0
Whoops, i'm sorry the link is working! Something was wrong here!
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Jack// ani
Thanks for reply Lord. Unfortunately link is dead!
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.
 
R

RST Engineering \(jw\)

Jan 1, 1970
0
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
 
R

Robert Monsen

Jan 1, 1970
0
Jack// ani said:
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?

Thanks

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 www.tech-chat.de)

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 www.tech-chat.de)

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.
 
M

mike

Jan 1, 1970
0
Robert said:
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 www.tech-chat.de)

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 www.tech-chat.de)

However, I think the first circuit is probably ok.

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

--
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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Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
ht<removethis>tp://www.geocities.com/SiliconValley/Monitor/4710/
 
F

Fred Bloggs

Jan 1, 1970
0
Jack// ani said:
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?

Thanks

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.
 
J

John Fields

Jan 1, 1970
0
John Fields wrote:

---
I understand the fascination with microcontrollers, but in an
application where one isn't warranted, it's just wasteful to design
one in. Consider the OP's application, a simple four-position
marquee scroller, and it becomes evident (to me, anyway) that $1 for
a PIC VS about fifty cents' worth of glue logic for the same
function makes the PIC unattractive. Plus, even with a free
programmer and development system there's still the learning curve
to climb.



It was another damn "use a PIC" post. Some of these posters drive
me crazy. Never a "Wow John, you sure put a lot of work into that,
nice job!" Never a complete project, with a schematic and source
code. Just "you could use a PIC". Hell, if you did what those
pic-ophiles do, your posts would say "use a soldering iron."
One thing's for sure - we can't criticize the PIC designs posted as
solutions to requests from posters. I'll tell you this, I'll put
any one of the solutions you've offered in the newsgroup against
all of the posted "PIC solutions", combined. Your solutions are
always great. Theirs are non-existant.

Ed
 
T

Terry Pinnell

Jan 1, 1970
0
It was another damn "use a PIC" post. Some of these posters drive
me crazy. Never a "Wow John, you sure put a lot of work into that,
nice job!" Never a complete project, with a schematic and source
code. Just "you could use a PIC". Hell, if you did what those
pic-ophiles do, your posts would say "use a soldering iron."
One thing's for sure - we can't criticize the PIC designs posted as
solutions to requests from posters. I'll tell you this, I'll put
any one of the solutions you've offered in the newsgroup against
all of the posted "PIC solutions", combined. Your solutions are
always great. Theirs are non-existant.
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:
http://www.terrypin.dial.pipex.com/Images/LED-Sequencer4MB.wmv
 
M

marika

Jan 1, 1970
0
Terry said:
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:
http://www.terrypin.dial.pipex.com/Images/LED-Sequencer4MB.wmv

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
 
B

Bob Monsen

Jan 1, 1970
0
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:
http://www.terrypin.dial.pipex.com/Images/LED-Sequencer4MB.wmv

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 <pic.h>

__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++;
}
 
C

Cliff

Jan 1, 1970
0
On Mon, 28 Nov 2005 14:51:55 -0600, John Field
On Mon, 28 Nov 2005 13:32:27 -0500, Cliff <[email protected] wrote

On Mon, 28 Nov 2005 00:56:50 GMT, David <[email protected] wrote

Characteristic impedance is purely a function of th
capacitance and inductance distributed along the line's length, an
would exist even if the dielectric were perfect (infinite paralle
resistance) and the wires superconducting (zero series resistance)
Velocity factor is a fractional value relating a transmission line'
propagation speed to the speed of light in a vacuum. Values rang
between 0.66 and 0.80 for typical two-wire lines and coaxial cables
For any cable type, it is equal to the reciprocal (1/x) of th squar
root of the relative permittivity of the cable's insulation.'

How odd then that the speed of propagation in conductor
varies

Not at all. Since resistivity varies between conductors because o
the materials of which they're composed and inductance varie
because of their diameters, why would 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 resistanc
but a fairly high speed of light
The speed of light goes down as things become more
conductive
 
F

Fred Abse

Jan 1, 1970
0
On Tue, 29 Nov 2005 07:31:11 +0000, Jasen Betts wrote
On 2005-11-27, Fred Abse <[email protected] wrote
On Sun, 27 Nov 2005 17:14:25 -0330, Gary wrote

David wrote

sni

Characteristic impedance and DC resistance are the same if the lin i
infinitely long and unterminated


Bullshit

If you mean by "DC resistance", the impedance you would see at th inpu
of an infinitely long line, it's not bullshit, it's perfectly true eve
if the line is made of zero-resistance conductors. You'll just se th
line's characteristic impedance

what about lines made of copper and plastic
Most are :-
ISTM that a few hundered kilometers if RG59 is going to measure mor
than 75 ohms even with far end is shorted

There's no way an infinite length will have a lower resistance
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
lik
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.

RG59-U.as

Version
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
C=20.5p
TEXT -162 506 Left 0 !.tran 0 1m 0 1
TEXT 496 456 Left 0 ;(Belden 8263

RG59U.pl

[Transient Analysis

Npanes:
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
GridStyle:
}

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
GridStyle:
}

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
GridStyle:
 
T

Terry Given

Jan 1, 1970
0
NunYa Bidness wrote
On 27 Nov 2005 18:27:46 -0800, "Kevin White <[email protected]
Gave us


Winfield Hill wrote

Since the electrons travel on the surface and multi-strand wir
has more surface area it should be better <

Only if the strands are insulated from one another


-
Thanks
- Wi

And also woven as in Litz wire. Otherwise the magnetic field wil
force the current to the outside of the bundle



It comes down to individual strands. If they are separated fro
each other electrically, the configuration of "the bundle" matter
not. The skin effect is exhibited in each strand, not in the bundl
as a group
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)
I
once hacked up a Mathcad worksheet that did exactly that, and i
agreed
well with messrs Vandelac & Ziogas. slow though :

if your argument were correct, multiple parallel strands of magne
wire
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
1"
OD, with many thousands of strands. the strands were woven int
smaller
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
were
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
Conductors that are in intimate electrical contact with each othe
along their length operate as a single strand and THAT bundle woul
"push" electron flow toward the outside of the bundle as increases
the bundle doesnt do the pushing, its the H field

Cheer
Terr
 
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