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On Friday 16 April 2004 01:13 pm, Stefan Trethan wrote:

I have two max038 lying around which wait only for me making a schematic
for a generator.

<...>

Is this the same sort of part as the Intersil (?) 8038?

<...>

It's similar but not the same. The intersil part is only 300kHz max.

Well, since I was primarily only interested in audio, that wasn't any big
deal...

I doubt you get the intersil part for free so why bother?

Because this was a bunch of years ago, when the parts you refer to weren't
available, and I doubt that I could've gotten it for free anyhow. Not that
it was all that expensive, it was sold at Radio Shack for a while and
could't have been more than a couple of dollars.

I dunno when i have time for designing the generator and making a pcb,
could be a long time...

The design was fun, I used an op amp and provided for a variable DC offset in
there. Also a logic-level output for sending slower pulses into TTL. The
board was one of those plug-in boards (44-pin edge connector) sold for
prototyping work. I've been messing with this stuff for a *long* time and
STILL haven't seen the need to make boards for stuff, unless I was going to
do a lot of some particular circuit, and it hasn't worked out that way.

I want to allow for modulation (although i most likely never ever need it
;-) ).

I didn't see that as being useful in what I intended to be an item of bench
test equipment. For a musical instrument, yeah, but that would be a
different project then.

The biggest problem now is the output stage, i have not designed such fast
circuits before, and i don't know how exactly to build it. i guess a opamp
would be easiest but i don't know if i can use it at 20Mhz just as i would
use it at audio frequency. need to think about it, and just now i have no
time..

That would take a very fast and expensive op amp, to be sure. Why go up that
high in terms of frequency? When I get up there I usually want some fixed
frequency and will likely use one of those crystal oscillator modules I have
a pile of here.

I only ordered the part to fill up the 8 item list having in the back of
my mind i need a generator.

What are you going to use it for that you want to go all the way up to 20 MHz?

I have two max038 lying around which wait only for me making a schematic
for a generator.
these are sine/triangle/square wave generators that work up to 20Mhz.
there is a cheaper version that works to 1Mhz which is sufficient for what
you need.

Is this the same sort of part as the Intersil (?) 8038? I built a generator
around one of those some years back, it was fairly simple, and it's very
flexible.

It's similar but not the same.
The intersil part is only 300kHz max.

I doubt you get the intersil part for free so why bother?

I dunno when i have time for designing the generator and making a pcb,
could be a long time...
I want to allow for modulation (although i most likely never ever need it ;-) ).

The biggest problem now is the output stage, i have not designed such fast circuits before,
and i don't know how exactly to build it. i guess a opamp would be easiest but i don't know
if i can use it at 20Mhz just as i would use it at audio frequency.
need to think about it, and just now i have no time..
I only ordered the part to fill up the 8 item list having in the back of my mind i need a generator.


ST

On Friday 16 April 2004 05:55 am, Stefan Trethan wrote:

On Fri, 16 Apr 2004 10:42:46 +0200 (MEST), Murat Ceylan

<hector@...> wrote:

Hello Everyone,

I'd like to build a signal generator that is not too professional but
good
enough for general use i.e. that can produce sine, sawtooth and square
waveforms in 1-50kHz range or so with reasonable reliability. Do you
happen
to have any schematics, suggestions, assembly tips etc.?

Many thanks in advance,
Murat

I have two max038 lying around which wait only for me making a schematic
for a generator.
these are sine/triangle/square wave generators that work up to 20Mhz.
there is a cheaper version that works to 1Mhz which is sufficient for what
you need.

Is this the same sort of part as the Intersil (?) 8038? I built a generator
around one of those some years back, it was fairly simple, and it's very
flexible.

On Wednesday 14 April 2004 07:55 pm, Curtis Sakima wrote:

I think THAT part is because even at "full brightness" ... the phase shift
mechanism of most dimmers *still* does not have enough shift to shift the
trigger point all the way to "zero" (IE: the lamp is a 95% ... but the pot
is banged all the way to "full". Can't increase the pot any more.).

Yes. You have to reach a certain voltage before the trigger device (DIAC or
whatever) will function...

On Wed, 14 Apr 2004 19:06:23 -0500, Curtis Sakima <csakima@...> wrote:

Not sure if a triac "creates" a phase offset between voltage and current.
AFAIK, a triac only PWM's the input voltage/current ... and that's what
"controls" the brightness of the lamp (heat from the heating element).

I thought only capacitive/inductive elements creates angle shifts .......??


Curtis

look at the input. approximate the signals with a sine and calculate the phase offset.
there will be some.

I never hooked one up on a wattmeter / phase offset meter, would be nice to know..
(but i have no such meter)

ST

On Fri, 16 Apr 2004 03:25:18 -0000, Jan Rowland <JanRwl@...> wrote:

Can anyone direct me to a 4 to 8 digit UP/DOWN counter, preferably
with LCD display, needing only a 5 VDC supply? Red Lion made
a "Super Sub-Cub" which met these requirements, but they appear to
have dropped that one for a "new design" with a HUGE $tag, which must
have at least 9 VDC supply. Thanks, Jan Rowland

there are 2 maxim ICS for such a thing.

it are 4 digit 25Mhz counter, available for LED or LCD.

icm7225 is for led and 7224 for lcd.


I'm not sure if it can count down, maybe you find another IC which can.

get them from maxim you know how.

ST

oh yes, 5V supply and no other components.

On Fri, 16 Apr 2004 10:42:46 +0200 (MEST), Murat Ceylan <hector@...> wrote:

Hello Everyone,

I'd like to build a signal generator that is not too professional but good
enough for general use i.e. that can produce sine, sawtooth and square
waveforms in 1-50kHz range or so with reasonable reliability. Do you happen
to have any schematics, suggestions, assembly tips etc.?

Many thanks in advance,
Murat

I have two max038 lying around which wait only for me making a schematic for a generator.
these are sine/triangle/square wave generators that work up to 20Mhz.
there is a cheaper version that works to 1Mhz which is sufficient for what you need.

But you can get the max038 for free as maxim samples so there is no need to cut corners.

which output amplitude do you need?

i plan to set up the second max038 as second independent generator but als selectable
to modulate the primary generator in frequency or amplitude.

You will want to look at the maxim datasheets and app. notes for the max038 and you
might want to search google with "frequency generator schematic".

ST

A TRIAC is a switching device which will generate harmonics in the
power drawn from the mains. Some of the power may be reactive power
but most is real power that light your bulb. The voltage and current
are both in phase even if waveform is a distorted.

No, the main voltage is not distorted. if you measute before the triac
there is a phase offset for every phase angle not 0 or 2*pi (more or less).

A motor will cause a phase offset between voltage and current because
it is a reactive load. So will a transformer, it is reactive too.

Then where does the reactive power in a triac circuit go? in a capacitive or inductive setup you
have some sort of energy storage. i don't see that in a triac circuit.

if you only take the first part of the fourier analysis of the signal (the first AC)
you get for the voltage the line voltage sine (if we assume it is not loaded down much
by the circuit) and for current you get the first sine approximation of the current the triac uses.
if we switch on at 50% of the sine this is definitely offset quite a bit.


i know the things you say about reactive power already, i'm just not seeing where it is going
in a triac circuit.
It looks to me like if at any given moment all the power =U*I in the load and thermal losses in the
triac. i just can't get reactive power here.


It seems a bit unlikely to me to convert reactive power to active power, this should be impossible.
So it seems there should not be any reactive power consumed by a triac circuit.
But if i look at the input it seems so..

ST

Hello Everyone,

I'd like to build a signal generator that is not too professional but good
enough for general use i.e. that can produce sine, sawtooth and square
waveforms in 1-50kHz range or so with reasonable reliability. Do you happen
to have any schematics, suggestions, assembly tips etc.?

Many thanks in advance,
Murat

--
NEU : GMX Internet.FreeDSL
Ab sofort DSL-Tarif ohne Grundgeb???hr:

I had a need to program some 64Kx8 Flash devices so I decided to hook
up an ATmega16 and use it to read and write the Flash. I put
together a quick web page describing what I did including links to
schematics and code which can be found at the link below.

The AVR code was written in C and compiled using the GNU C compiler
that is part of WinAVR. The other software component is a Win32
console app written in C and compiled using MSVC.

Members,
Can you pls let me know that on practical basis -when do we use servo
otors,and when stepper motors...What is the exact difference in both with
the dc motors?cost wise(INR)

I had gone through a few pages and this is what I came to know-please
correct me-

Servo for angular motion only,contain gears too inbuilt..
steppers for step and digital motions only...

Regards
Swapan

Can anyone direct me to a 4 to 8 digit UP/DOWN counter, preferably
with LCD display, needing only a 5 VDC supply? Red Lion made
a "Super Sub-Cub" which met these requirements, but they appear to
have dropped that one for a "new design" with a HUGE $tag, which must
have at least 9 VDC supply. Thanks, Jan Rowland

--- In Electronics_101@..., Stefan Trethan
<stefan_trethan@g...> wrote:

On Wed, 14 Apr 2004 19:18:18 -0400, Roy J. Tellason
<rtellason@b...> wrote:

On Wednesday 14 April 2004 06:59 pm, manifold wrote:

That would mean that the output would always have a notch out of the
of the applied voltage waveform and that notch height would be equal
to the threshold voltage. The notch location would be determined by
the value of the DC gate voltage up the limit of 10V.

Seems to me that with any kind of a triac circuit you're *always*

going

to
have a bit of a notch, in that the applied voltage has to rise to a
certain
point before triggering can take place...

This is why there are times when I'll get interference from a lamp

dimmer

here, no matter where it's set -- even "full on".

yes, true, the effect is not that much compared to 240Veff line

voltage...

also you need sufficient inductance and maybe filtering for EMC.

One thing to keep in mind is that a system using phase angle control

(like

a triac)
can produce a phase offset between voltage and current and you draw
reactive power.
the interesting thing is you have nothing to store this energy in so it
seems to be converted
to heat/light which is efective power. this seems a bit odd to me

because

it should not be possible
tu "use" reactive power to gain energy. another thing is that the kWh
meter which measures how much
you will pay does not seem to measure reactive power.

This is one point i need to think about some day... It's in the back of
the mind but i never
really thoght it through if it is correct.

ST

A TRIAC is a switching device which will generate harmonics in the
power drawn from the mains. Some of the power may be reactive power
but most is real power that light your bulb. The voltage and current
are both in phase even if waveform is a distorted.

A motor will cause a phase offset between voltage and current because
it is a reactive load. So will a transformer, it is reactive too.

No, you are not charged for reactive power. You never get to use
reactive power, you always have to give it back, so you don't get
charged for it. Reactive power is not converted into light or heat, if
it were than it becomes real power and you get charged for it. There
are a lot of jokes about reactive power and how to make money from
generating reactive power instead of real power.

You may get charged for reactive power if you are a big industry and
the utility has to put in new equipment to cover your reactive power
needs. Remember the transformers, conductors, capacitive compensators,
etc., all have to be able to deliver the total amount of power, real
and imaginary (reactive).

(2) Varying only two resistors (one for frequency and the other for
offset) is a very optimal solution already. You may not be able to
do better.

You are probably right. One thing to watch out for is the stray
capacitance of digitally variable resistors and multiplexers which can
affect your filtering.

Keith.

On Wed, 14 Apr 2004 19:18:18 -0400, Roy J. Tellason <rtellason@...> wrote:

On Wednesday 14 April 2004 06:59 pm, manifold wrote:

That would mean that the output would always have a notch out of the
of the applied voltage waveform and that notch height would be equal
to the threshold voltage. The notch location would be determined by
the value of the DC gate voltage up the limit of 10V.

Seems to me that with any kind of a triac circuit you're *always* going to
have a bit of a notch, in that the applied voltage has to rise to a certain
point before triggering can take place...

This is why there are times when I'll get interference from a lamp dimmer
here, no matter where it's set -- even "full on".

yes, true, the effect is not that much compared to 240Veff line voltage...
also you need sufficient inductance and maybe filtering for EMC.

One thing to keep in mind is that a system using phase angle control (like a triac)
can produce a phase offset between voltage and current and you draw reactive power.
the interesting thing is you have nothing to store this energy in so it seems to be converted
to heat/light which is efective power. this seems a bit odd to me because it should not be possible
tu "use" reactive power to gain energy. another thing is that the kWh meter which measures how much
you will pay does not seem to measure reactive power.

This is one point i need to think about some day... It's in the back of the mind but i never
really thoght it through if it is correct.

ST

On Wed, 14 Apr 2004 22:59:36 -0000, manifold <manifold_1@...> wrote:

You're right, A DC voltage applied to the gate will allow the TRIAC to
conduct in both directions as long as the applied voltage gets over
the threshold voltage. I guess I have just never used one like that
and did not think through the analogous SCR circuit well enough (duh).

That would mean that the output would always have a notch out of the
of the applied voltage waveform and that notch height would be equal
to the threshold voltage. The notch location would be determined by
the value of the DC gate voltage up the limit of 10V.

Is that right?

dunno...

will have to actually try it when i need it.

i thought a scr is current triggered, not voltage triggered, is that right?

If you think it through with two seperate SCRs it looks like it will not work
but a triac is not exactly only 2 scrs, like a bipolar transistor is not only two diodes.

It might just be that with the opposite polarity of the trigger pulse the other PN junction
might be used, which would mean with DC trigger always the same junction is used to trigger,
no matter which direction the main current is...


not sure myself...

ST

Not sure if a triac "creates" a phase offset between voltage and current.
AFAIK, a triac only PWM's the input voltage/current ... and that's what
"controls" the brightness of the lamp (heat from the heating element).

I thought only capacitive/inductive elements creates angle shifts .......??


Curtis

Dazzle Mom this coming Mother's Day season with flowers!

I think THAT part is because even at "full brightness" ... the phase shift
mechanism of most dimmers *still* does not have enough shift to shift the
trigger point all the way to "zero" (IE: the lamp is a 95% ... but the pot
is banged all the way to "full". Can't increase the pot any more.).

Curtis

Dazzle Mom this coming Mother's Day season with flowers!

On Wednesday 14 April 2004 06:59 pm, manifold wrote:

That would mean that the output would always have a notch out of the
of the applied voltage waveform and that notch height would be equal
to the threshold voltage. The notch location would be determined by
the value of the DC gate voltage up the limit of 10V.

Seems to me that with any kind of a triac circuit you're *always* going to
have a bit of a notch, in that the applied voltage has to rise to a certain
point before triggering can take place...

This is why there are times when I'll get interference from a lamp dimmer
here, no matter where it's set -- even "full on".

You're right, A DC voltage applied to the gate will allow the TRIAC to
conduct in both directions as long as the applied voltage gets over
the threshold voltage. I guess I have just never used one like that
and did not think through the analogous SCR circuit well enough (duh).

That would mean that the output would always have a notch out of the
of the applied voltage waveform and that notch height would be equal
to the threshold voltage. The notch location would be determined by
the value of the DC gate voltage up the limit of 10V.

Is that right?

--- In Electronics_101@..., "Curtis Sakima" <csakima@m...>
wrote:

I dunno. If I recall correctly, a DC signal should work just fine.

You

just won't be using one of the quadrants that "every other Joe"

usually uses

(the negative MT/negative gate). You'd be using the negative

MT/POSITIVE

gate quadrant.

Curtis

Dazzle Mom this coming Mother's Day season with flowers!




----- Original Message -----
From: manifold <manifold_1@y...>

No, A DC gate signal will not 'turn on the TRIAC' it will only

rectify the

current to the load if the power source is from the AC mains. A

TRIAC is the

same as two reverse parallel SCRs. If a DC gate signal is applied,

only one

of the 'SCR halves' will ever turn on.