I'm new here but have searched these archives and don't see a 555
based inverter. I'm trying to design a very specific circuit which
has and input of about 9vdc, battery or adapter, that outputs 30vac
16 hz preferably sign wave but square will probably works just fine,
but the current must be limited to less than 1mA at all times. I
have managed to get a nice square wave out of the 555 chip with less
than .46% difference in T1 and T2 ( time for the pos. and neg. wave)
and filtered it to a fair sine wave. I had hoped that by limiting
the input to a step-up transformer (to get 30v) I could get the
current limiting on the other side, wrong. It limits both voltage
and current on the output side. A resistor in parallel with the load
won't do because the load varies. So, having said all the above I
guess my question is does anyone know of a current limiting circuit
for the above conditions? Or, am I taking the wrong approach
entirely in the circuit design. Also, does anyone know a good source
for a 1 to 4 or 3 step-up transformer (small).
Help!, U4ia

On Sun, 25 Apr 2004 16:18:10 -0000, genteelu4ia <vortex_9x@...> wrote:

I'm new here but have searched these archives and don't see a 555
based inverter. I'm trying to design a very specific circuit which
has and input of about 9vdc, battery or adapter, that outputs 30vac
16 hz preferably sign wave but square will probably works just fine,
but the current must be limited to less than 1mA at all times. I
have managed to get a nice square wave out of the 555 chip with less
than .46% difference in T1 and T2 ( time for the pos. and neg. wave)
and filtered it to a fair sine wave. I had hoped that by limiting
the input to a step-up transformer (to get 30v) I could get the
current limiting on the other side, wrong. It limits both voltage
and current on the output side. A resistor in parallel with the load
won't do because the load varies. So, having said all the above I
guess my question is does anyone know of a current limiting circuit
for the above conditions? Or, am I taking the wrong approach
entirely in the circuit design. Also, does anyone know a good source
for a 1 to 4 or 3 step-up transformer (small).
Help!, U4ia

current limiting does imply voltage changes.
If you have a given load and limit the current the voltage will adjust
according to U=R*I if the current limit is exceeded.

You want never more than 1mA at the 30V output side?
then you need to limit the input to 4 or 3 * 1A.

You could try to limit the supply to the 555, but i am not sure what will happen if the
load varies a lot.
Best idea might be to limit the 555 output.
You only need to limit the on-time, because the transformer will only take the AC.
There are many methods, using a transistor or a fet and some sort of sense resistor.

There are circuits for 50% duty cycle for the 555.

A small stepup transformer you might find in telephone applications.
these are small transformers for audio (2khz but i reckon a bit more is possible).
they have different windings, i think you can very well combine them to your needs.
most time they have one primary and two secondary.

good luck

ST

Thanks for your prompt reply, Stefan;

Your right I suppose actually I only need a 30v potential and I
already have what I need. Actually the out-put of the 555 goes to
the base of two transistors one PNP and the other NPN which in turn
control the input to the transformer. Right now (on the breadboard)
there is a pot. that controls both in-put and out-put of the
transformer I just have to feed the trans. out-put back to the bases
to make it automatic-- inversely that is. Probably get some kind of
hysterisis going and the thing will blow-up in my face.<grin> Next
is the holding circuit. I did find a Hammond audio transformer with
1 to 3 ratio but they want $75.00 for it (WOW) and I'm looking for
something much cheaper.
Thanks again, U4ia

From: Stefan Trethan <stefan_trethan@g...>
Date: Sun Apr 25, 2004 11:41 am
Subject: Re: [Electronics_101] Help! 555 inverter

On Sun, 25 Apr 2004 16:18:10 -0000, genteelu4ia <vortex_9x@h...>
wrote:

I'm new here but have searched these archives and don't see a 555
based inverter. I'm trying to design a very specific circuit which
has and input of about 9vdc, battery or adapter, that outputs 30vac
16 hz preferably sign wave but square will probably works just

fine,

but the current must be limited to less than 1mA at all times. I
have managed to get a nice square wave out of the 555 chip with

less

than .46% difference in T1 and T2 ( time for the pos. and neg.

wave)

and filtered it to a fair sine wave. I had hoped that by limiting
the input to a step-up transformer (to get 30v) I could get the
current limiting on the other side, wrong. It limits both voltage
and current on the output side. A resistor in parallel with the

load

won't do because the load varies. So, having said all the above I
guess my question is does anyone know of a current limiting circuit
for the above conditions? Or, am I taking the wrong approach
entirely in the circuit design. Also, does anyone know a good

source

for a 1 to 4 or 3 step-up transformer (small).
Help!, U4ia

current limiting does imply voltage changes.
If you have a given load and limit the current the voltage will
adjust
according to U=R*I if the current limit is exceeded.

You want never more than 1mA at the 30V output side?
then you need to limit the input to 4 or 3 * 1A.

You could try to limit the supply to the 555, but i am not sure what
will
happen if the
load varies a lot.
Best idea might be to limit the 555 output.
You only need to limit the on-time, because the transformer will
only take
the AC.
There are many methods, using a transistor or a fet and some sort of
sense
resistor.

There are circuits for 50% duty cycle for the 555.

A small stepup transformer you might find in telephone applications.
these are small transformers for audio (2khz but i reckon a bit more
is
possible).
they have different windings, i think you can very well combine them
to
your needs.
most time they have one primary and two secondary.

good luck

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

On Sun, 25 Apr 2004 16:18:10 -0000, genteelu4ia <vortex_9x@h...>
wrote:

I'm new here but have searched these archives and don't see a 555
based inverter. I'm trying to design a very specific circuit

which

has and input of about 9vdc, battery or adapter, that outputs

30vac

16 hz preferably sign wave but square will probably works just

fine,

but the current must be limited to less than 1mA at all times. I
have managed to get a nice square wave out of the 555 chip with

less

than .46% difference in T1 and T2 ( time for the pos. and neg.

wave)

and filtered it to a fair sine wave. I had hoped that by limiting
the input to a step-up transformer (to get 30v) I could get the
current limiting on the other side, wrong. It limits both voltage
and current on the output side. A resistor in parallel with the

load

won't do because the load varies. So, having said all the above I
guess my question is does anyone know of a current limiting

circuit

for the above conditions? Or, am I taking the wrong approach
entirely in the circuit design. Also, does anyone know a good

source

for a 1 to 4 or 3 step-up transformer (small).
Help!, U4ia

current limiting does imply voltage changes.
If you have a given load and limit the current the voltage will

adjust

according to U=R*I if the current limit is exceeded.

You want never more than 1mA at the 30V output side?
then you need to limit the input to 4 or 3 * 1A.

You could try to limit the supply to the 555, but i am not sure

what will

happen if the
load varies a lot.
Best idea might be to limit the 555 output.
You only need to limit the on-time, because the transformer will

only take

the AC.
There are many methods, using a transistor or a fet and some sort

of sense

resistor.

There are circuits for 50% duty cycle for the 555.

A small stepup transformer you might find in telephone

applications.

these are small transformers for audio (2khz but i reckon a bit

more is

possible).
they have different windings, i think you can very well combine

them to

your needs.
most time they have one primary and two secondary.

good luck

ST

On Sun, 25 Apr 2004 18:24:56 -0000, genteelu4ia <vortex_9x@...> wrote:

Thanks for your prompt reply, Stefan;

Your right I suppose actually I only need a 30v potential and I
already have what I need. Actually the out-put of the 555 goes to
the base of two transistors one PNP and the other NPN which in turn
control the input to the transformer. Right now (on the breadboard)
there is a pot. that controls both in-put and out-put of the
transformer I just have to feed the trans. out-put back to the bases
to make it automatic-- inversely that is. Probably get some kind of
hysterisis going and the thing will blow-up in my face.<grin> Next
is the holding circuit. I did find a Hammond audio transformer with
1 to 3 ratio but they want $75.00 for it (WOW) and I'm looking for
something much cheaper.
Thanks again, U4ia

not sure about your schematic, and the requirements...

Can't you find such a telephone transformer?
They can be found in old modems, and some old phones.
I think i pulled a couple out of a very old answering machine.

they are about an inch to two inches wide cube.
current and voltage rating would be about what you need.

ST

Thanks again, Stefan;

Isn't it always true that one saves piles of electonic junk and the
part one needs isn't there-- well it is for me.<grin> I'll find one
I'm sure but I may need a wholesale source for lot's of them.

Thanks Again, U4ia

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

On Sun, 25 Apr 2004 18:24:56 -0000, genteelu4ia <vortex_9x@h...>
wrote:

Thanks for your prompt reply, Stefan;

Your right I suppose actually I only need a 30v potential and I
already have what I need. Actually the out-put of the 555 goes to
the base of two transistors one PNP and the other NPN which in

turn

control the input to the transformer. Right now (on the

breadboard)

there is a pot. that controls both in-put and out-put of the
transformer I just have to feed the trans. out-put back to the

bases

to make it automatic-- inversely that is. Probably get some kind

of

hysterisis going and the thing will blow-up in my face.<grin>

Next

is the holding circuit. I did find a Hammond audio transformer

with

1 to 3 ratio but they want $75.00 for it (WOW) and I'm looking

for

something much cheaper.
Thanks again, U4ia

not sure about your schematic, and the requirements...

Can't you find such a telephone transformer?
They can be found in old modems, and some old phones.
I think i pulled a couple out of a very old answering machine.

they are about an inch to two inches wide cube.
current and voltage rating would be about what you need.

ST

Been casually following this thread and .....

Curious how the 555 goes to the "NPN and PNP transistor". I'm guessing
you have it hooked up as a complementary/symmetry (like the output of a
audio amp)??

Second, what do you mean by, "I just have to feed the trans. out-put back to
the bases to make it automatic-- inversely that is"?? Feeding back to the
bases would imply that you're making a transistor-astable-oscillator.
<Thinking>But why would you need to have the tranny's oscillate .... when
it's the 555 that does the "oscillating"?? Aren't the trannys just for
power out's??

Curtis

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

On Sunday 25 April 2004 02:24 pm, genteelu4ia wrote:

I did find a Hammond audio transformer with 1 to 3 ratio but they want
$75.00 for it (WOW) and I'm looking for something much cheaper.

It's been some time since I looked in one of their catalogs, but I seem to
recall that Mouser has some fairly inexpensive audio transformers. *WAY*
cheaper than the figure you mention... :-)

Curtis;

Don't know beans about an audio amp. but the 555 square wave at pin
3 is hook to the bases of the transistors whos emitters are
connected. The collector of the NPN goes to + source, the collector
of the PNP goes to ground, the wave out-put is taken from between
the two transistors at the emitters. That's off the top of my head.
I could send you a .gif circuit diagram if that's not clear.
As far as the feed back; I don't know what I'm talking about-- I
invisioned using the out-put of the transformer to control it's
current by feeding it back to control it's in-put-- havent worked
that out yet. But, so far the circuit is working fine as calculated.

U4ia
--- In Electronics_101@..., "Curtis Sakima"
<csakima@m...> wrote:

Been casually following this thread and .....

Curious how the 555 goes to the "NPN and PNP transistor". I'm

guessing

you have it hooked up as a complementary/symmetry (like the output

of a

audio amp)??

Second, what do you mean by, "I just have to feed the trans. out-

put back to

the bases to make it automatic-- inversely that is"?? Feeding

back to the

bases would imply that you're making a transistor-astable-

oscillator.

<Thinking>But why would you need to have the tranny's

oscillate .... when

it's the 555 that does the "oscillating"?? Aren't the trannys

just for

power out's??

Curtis

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




----- Original Message -----
From: genteelu4ia <vortex_9x@h...>
To: <Electronics_101@...>
Sent: Sunday, April 25, 2004 1:24 PM
Subject: [Electronics_101] Re: Help! 555 inverter

Thanks for your prompt reply, Stefan;

Your right I suppose actually I only need a 30v potential and I
already have what I need. Actually the out-put of the 555 goes to
the base of two transistors one PNP and the other NPN which in

turn

control the input to the transformer. Right now (on the

breadboard)

there is a pot. that controls both in-put and out-put of the
transformer I just have to feed the trans. out-put back to the

bases

to make it automatic-- inversely that is. Probably get some kind

of

hysterisis going and the thing will blow-up in my face.<grin>

Next

is the holding circuit. I did find a Hammond audio transformer

with

1 to 3 ratio but they want $75.00 for it (WOW) and I'm looking

for

something much cheaper.
Thanks again, U4ia

From: Stefan Trethan <stefan_trethan@g...>
Date: Sun Apr 25, 2004 11:41 am
Subject: Re: [Electronics_101] Help! 555 inverter

On Sun, 25 Apr 2004 16:18:10 -0000, genteelu4ia <vortex_9x@h...>
wrote:

I'm new here but have searched these archives and don't see a

555

based inverter. I'm trying to design a very specific circuit

which

has and input of about 9vdc, battery or adapter, that outputs

30vac

16 hz preferably sign wave but square will probably works just

fine,

but the current must be limited to less than 1mA at all times.

I

have managed to get a nice square wave out of the 555 chip with

less

than .46% difference in T1 and T2 ( time for the pos. and neg.

wave)

and filtered it to a fair sine wave. I had hoped that by

limiting

the input to a step-up transformer (to get 30v) I could get the
current limiting on the other side, wrong. It limits both

voltage

and current on the output side. A resistor in parallel with the

load

won't do because the load varies. So, having said all the

above I

guess my question is does anyone know of a current limiting

circuit

for the above conditions? Or, am I taking the wrong approach
entirely in the circuit design. Also, does anyone know a good

source

for a 1 to 4 or 3 step-up transformer (small).
Help!, U4ia

current limiting does imply voltage changes.
If you have a given load and limit the current the voltage will
adjust
according to U=R*I if the current limit is exceeded.

You want never more than 1mA at the 30V output side?
then you need to limit the input to 4 or 3 * 1A.

You could try to limit the supply to the 555, but i am not sure

what

will
happen if the
load varies a lot.
Best idea might be to limit the 555 output.
You only need to limit the on-time, because the transformer will
only take
the AC.
There are many methods, using a transistor or a fet and some

sort of

sense
resistor.

There are circuits for 50% duty cycle for the 555.

A small stepup transformer you might find in telephone

applications.

these are small transformers for audio (2khz but i reckon a bit

more

is
possible).
they have different windings, i think you can very well combine

them

to
your needs.
most time they have one primary and two secondary.

good luck

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

On Sun, 25 Apr 2004 16:18:10 -0000, genteelu4ia

<vortex_9x@h...>

wrote:

I'm new here but have searched these archives and don't see

a 555

based inverter. I'm trying to design a very specific circuit

which

has and input of about 9vdc, battery or adapter, that outputs

30vac

16 hz preferably sign wave but square will probably works

just

fine,

but the current must be limited to less than 1mA at all

times. I

have managed to get a nice square wave out of the 555 chip

with

less

than .46% difference in T1 and T2 ( time for the pos. and

neg.

wave)

and filtered it to a fair sine wave. I had hoped that by

limiting

the input to a step-up transformer (to get 30v) I could get

the

current limiting on the other side, wrong. It limits both

voltage

and current on the output side. A resistor in parallel with

the

load

won't do because the load varies. So, having said all the

above I

guess my question is does anyone know of a current limiting

circuit

for the above conditions? Or, am I taking the wrong approach
entirely in the circuit design. Also, does anyone know a good

source

for a 1 to 4 or 3 step-up transformer (small).
Help!, U4ia

current limiting does imply voltage changes.
If you have a given load and limit the current the voltage will

adjust

according to U=R*I if the current limit is exceeded.

You want never more than 1mA at the 30V output side?
then you need to limit the input to 4 or 3 * 1A.

You could try to limit the supply to the 555, but i am not sure

what will

happen if the
load varies a lot.
Best idea might be to limit the 555 output.
You only need to limit the on-time, because the transformer

will

only take

the AC.
There are many methods, using a transistor or a fet and some

sort

of sense

resistor.

There are circuits for 50% duty cycle for the 555.

A small stepup transformer you might find in telephone

applications.

these are small transformers for audio (2khz but i reckon a bit

more is

possible).
they have different windings, i think you can very well combine

them to

your needs.
most time they have one primary and two secondary.

good luck

ST

Yahoo! Groups Links

why not use a small mains transformer?

Your talking to a novice here, what's a mains transformer and where
would one find one?

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

why not use a small mains transformer?

On Sun, 25 Apr 2004 15:45:50 -0400, Roy J. Tellason
<rtellason@b...> wrote:

On Sunday 25 April 2004 02:24 pm, genteelu4ia wrote:

I did find a Hammond audio transformer with 1 to 3 ratio but

they want

$75.00 for it (WOW) and I'm looking for something much cheaper.

It's been some time since I looked in one of their catalogs,

but I seem

to
recall that Mouser has some fairly inexpensive audio

transformers. *WAY*

cheaper than the figure you mention... :-)













Yahoo! Groups Links

Why not wind your own..

Coming from a radio background I make use of the ferrite cores that
everyone puts in the bin. The type used on monitor cables and power
cables.
A role of copper coated wire and abit of time and you on your way..

Gary

开云体育

i meant a small power transformer, e.g. 110V to 25V.
use it reverse, and of course overdimensioned for the low frequency and dc dissipation.

ST

thought he said 16Hz.... ferrite ain't no good, low saturation flux.

ST

Don't know if this helps, but I made a high voltage supply with a 555,
power NPN, and small transformer. Since it just had to charge and hold
(for a Xenon flash circuit), the voltage feedback was just a 120V
zener to the enable input of the 555.

It was wired to generate a voltage negative with respect to ground. It
reaches Zener breakdown, it pulls the Enable input of the 555 low and
stops oscillation.

I did sort of a delayed hysteresis. The zener had a resistor in series
with it to limit current, and there was a capacitor from the 555
Enable input to ground. The delay created by that series resistor and
the capacitor meant it kept charging for a fraction of a second after
reaching zener breakdown.

It's very important to note that there were two diodes on the Enable
input wired to limit voltage there so it was always between ground and
V+, within a diode drop.

All designed to be extremely low current, it rarely had to turn on
again to top off the High Voltage capacitor when not being "fired".

This was for a Sci Fi prop blaster. I just left it on all weekend at
conventions.

It could be isolated by using an optoisolator.

You could wind your own transformer. I have always found Amidon's info
to be very helpful.


Alien Steve

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

Been casually following this thread and .....

Curious how the 555 goes to the "NPN and PNP transistor". I'm

guessing

you have it hooked up as a complementary/symmetry (like the output of a
audio amp)??

Second, what do you mean by, "I just have to feed the trans. out-put

back to

the bases to make it automatic-- inversely that is"?? Feeding back

to the

bases would imply that you're making a transistor-astable-oscillator.
<Thinking>But why would you need to have the tranny's oscillate ....

when

it's the 555 that does the "oscillating"?? Aren't the trannys just for
power out's??

Curtis

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




----- Original Message -----
From: genteelu4ia <vortex_9x@h...>
To: <Electronics_101@...>
Sent: Sunday, April 25, 2004 1:24 PM
Subject: [Electronics_101] Re: Help! 555 inverter

Thanks for your prompt reply, Stefan;

Your right I suppose actually I only need a 30v potential and I
already have what I need. Actually the out-put of the 555 goes to
the base of two transistors one PNP and the other NPN which in turn
control the input to the transformer. Right now (on the breadboard)
there is a pot. that controls both in-put and out-put of the
transformer I just have to feed the trans. out-put back to the bases
to make it automatic-- inversely that is. Probably get some kind of
hysterisis going and the thing will blow-up in my face.<grin> Next
is the holding circuit. I did find a Hammond audio transformer with
1 to 3 ratio but they want $75.00 for it (WOW) and I'm looking for
something much cheaper.
Thanks again, U4ia

Except they are extremely inefficient at higher frequencies, and very
large and heavy. Actually they are even inefficient at 50/60Hz, that
frequency was a trade off as higher frequencies meant smaller more
efficient transformers, but much higher transmission losses due to
things like capacitive and inductive losses.

Alien Steve

--- In Electronics_101@..., "Gary Anderson (G)"
<andersg@t...> wrote:

A mains transformer is that kinda that you find in all your electrical
appliances.. eg Video machines, DVD players etc.. The heavy goodie
where the wire from the plug from the wall connects to and drops the
voltage down from 220V to 12 or 9..
Normal has a piece of plastic over the terminal warning you.. DANGER
HIGH VOLTAGE.. << Funny how a person reads it and still shocks
HAHA>>

Gary

On Sunday 25 April 2004 03:59 pm, Gary Anderson (G) wrote:

Why not wind your own..

Coming from a radio background I make use of the ferrite cores that
everyone puts in the bin. The type used on monitor cables and power
cables.
A role of copper coated wire and abit of time and you on your way..

Why not start with a lump of copper and draw your own wire while you're at it?
This is getting silly...

Oh Ok, a what I call power transformer, that's what I'm using now
but it's hard to find one with the right ratio because the power
transformers run off of 120v so lets see that's a 40v to make 3 to 1
or 30v at 4 to 1 ratio. I'm using a CT 8X8/120X230 now but it kinda
big. But, with the current limiting it cuts down the voltage nicely.
Thanks, U4ia

--- In Electronics_101@..., "Gary Anderson (G)"
<andersg@t...> wrote:

A mains transformer is that kinda that you find in all your

electrical

appliances.. eg Video machines, DVD players etc.. The heavy goodie
where the wire from the plug from the wall connects to and drops

the

voltage down from 220V to 12 or 9..
Normal has a piece of plastic over the terminal warning you..

DANGER

HIGH VOLTAGE.. << Funny how a person reads it and still shocks
HAHA>>

Gary




-----Original Message-----
From: genteelu4ia [mailto:vortex_9x@h...]
Sent: Sunday, April 25, 2004 9:58 PM
To: Electronics_101@...
Subject: [Electronics_101] Re: Help! 555 inverter

Your talking to a novice here, what's a mains transformer and

where

would one find one?

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

why not use a small mains transformer?

On Sun, 25 Apr 2004 15:45:50 -0400, Roy J. Tellason
<rtellason@b...> wrote:

On Sunday 25 April 2004 02:24 pm, genteelu4ia wrote:

I did find a Hammond audio transformer with 1 to 3 ratio but

they want

$75.00 for it (WOW) and I'm looking for something much

cheaper.

It's been some time since I looked in one of their catalogs,

but I seem

to
recall that Mouser has some fairly inexpensive audio

transformers. *WAY*

cheaper than the figure you mention... :-)













Yahoo! Groups Links

_____

Yahoo! Groups Links
* To visit your group on the web, go to:


* To unsubscribe from this group, send an email to:
Electronics_101-unsubscribe@...
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subject=Unsubscrib

e>

* Your use of Yahoo! Groups is subject to the Yahoo! Terms

of

Service <> .

--- In Electronics_101@..., "Roy J. Tellason"
<rtellason@b...> wrote:

On Sunday 25 April 2004 03:59 pm, Gary Anderson (G) wrote:

Why not wind your own..

Coming from a radio background I make use of the ferrite cores that
everyone puts in the bin. The type used on monitor cables and power
cables.
A role of copper coated wire and abit of time and you on your way..

Why not start with a lump of copper and draw your own wire while

you're at it?

This is getting silly...

If you think it is silly, you don't -have- to enter every discussion.

This list is about learning electronics.

Alien Steve

Now, Now, Roy,

In the radio days that's what it took to get the job done and those
guys didn't have it handed to them on a silver platter like we do.
My hat is off to them. But, today your right <grin>
U4ia
--- In Electronics_101@..., "Roy J. Tellason"
<rtellason@b...> wrote:

On Sunday 25 April 2004 03:59 pm, Gary Anderson (G) wrote:

Why not wind your own..

Coming from a radio background I make use of the ferrite cores

that

everyone puts in the bin. The type used on monitor cables and

power

cables.
A role of copper coated wire and abit of time and you on your

way..

Why not start with a lump of copper and draw your own wire while

you're at it?

This is getting silly...