change polarity@15 mins on DC transformer<total beginner--single project>

[[email protected]]

Hi,

I have a little transformer putting out 3 volts DC from 240 volt AC mains and I want to change the polarity from positive to negative every 15 minutes in a continuous cycle.

This is the first time for me and it's a one off project. I would

like to do it as easily as possible--with instructions a child could
follow if that's ok. Is it possible to do it with a 'plug in'
'breadboard' ? (I don't even own a soldering iron--or meter).

Dick Smith Electronics has a kit called the 'Discovery series' K2813--Discovery Series Kit Multi 555 Timer for $20.

<Circuit uses a 555 timer IC as a building block for timer projects.
Supplied with components and PCB.>

Is this what I need to buy? --should set the time interval...

But to change the polarity? I wouldn't have a clue. I read you need a capacitor. [the transformer has a little pot that you turn with a screwdriver] I can unscrew its case--but its very fiddly and fragile-looking inside--maybe I should start over and get a kit transformer too--I found these on the DSE catalogue... but I'm not sure if they're AC to DC--

1.) <General Purpose Transformer 12-0-12V @ 3.6VA
Secondary output: 12-0-12 volts. Secondary current: 150mA.
Terminations: flying leads.>
Related Searches: transformer | transformer 12 volt M2854$4.98>2.) < Transformer 0-24V @ 3A
Secondary output: 0-24 volts. Secondary current: 3 amps. Terminations:
solder lugs.> M2158.
Sorry I don't know more. Thanks for your help.

 

[Andy Wood]

Hi,

I have a little transformer putting out 3 volts DC from 240 volt AC mains and I want to change the polarity from positive to negative every 15 minutes in a continuous cycle.

This is the first time for me and it's a one off project. I would

like to do it as easily as possible--with instructions a child could
follow if that's ok. Is it possible to do it with a 'plug in'
'breadboard' ? (I don't even own a soldering iron--or meter).

Dick Smith Electronics has a kit called the 'Discovery series' K2813--Discovery Series Kit Multi 555 Timer for $20.

<Circuit uses a 555 timer IC as a building block for timer projects.
Supplied with components and PCB.>

Is this what I need to buy? --should set the time interval...

But to change the polarity? I wouldn't have a clue. I read you need a capacitor. [the transformer has a little pot that you turn with a screwdriver] I can unscrew its case--but its very fiddly and fragile-looking inside--maybe I should start over and get a kit transformer too--I found these on the DSE catalogue... but I'm not sure if they're AC to DC--

1.) <General Purpose Transformer 12-0-12V @ 3.6VA
Secondary output: 12-0-12 volts. Secondary current: 150mA.
Terminations: flying leads.>
Related Searches: transformer | transformer 12 volt M2854$4.98>2.) < Transformer 0-24V @ 3A
Secondary output: 0-24 volts. Secondary current: 3 amps. Terminations:
solder lugs.> M2158.
Sorry I don't know more. Thanks for your help.

DSE M2854 and M2158 are transformers and nothing more - AC in and AC
out. And since you admit you don't have a clue, I suggest you steer
clear of them because to connect them you have to work with mains
wiring - dangerous if you don't know what you are doing.
Andy Wood
[email protected]

 

[David L. Jones]

Hi,

like to do it as easily as possible--with instructions a child could
follow if that's ok. Is it possible to do it with a 'plug in'
'breadboard' ? (I don't even own a soldering iron--or meter).

Not easily. You'll almost certainly have to do some soldering.
"Breadboards" are just a temporary way to trial a circuit, it's not a
permanant solution.

<Circuit uses a 555 timer IC as a building block for timer projects.
Supplied with components and PCB.>

You'll need some sort of timer like this, yes.

But to change the polarity? I wouldn't have a clue. I read you need a capacitor. [the transformer has a little pot that you turn with a screwdriver] I can unscrew its case--but its very fiddly and fragile-looking inside--maybe I should start over and get a kit transformer too--I found these on the DSE catalogue... but I'm not sure if they're AC to DC--

You could use a DPDT relay to reverse the contacts to the DC plug.

Dave

 

[[email protected]]

use the 555 to switch a

small relay with two sets of change over contacts
or use 4 transistors in a full bridge configuration

Thanks--but I need specific help--on circuit design and exactly which
components to buy. Ideally I would use a pre-bought transformer and
just add the polarity switching circuit at the dc end--that way it's
idiot-proof 240 volt-wise. Is this possible?

Hi,

like to do it as easily as possible--with instructions a child could
follow if that's ok. Is it possible to do it with a 'plug in'
'breadboard' ? (I don't even own a soldering iron--or meter).

Not easily. You'll almost certainly have to do some soldering.
"Breadboards" are just a temporary way to trial a circuit, it's not a
permanant solution.

<Circuit uses a 555 timer IC as a building block for timer projects.
Supplied with components and PCB.>

You'll need some sort of timer like this, yes.

But to change the polarity? I wouldn't have a clue. I read you need a capacitor. [the transformer has a little pot that you turn with a screwdriver] I can unscrew its case--but its very fiddly and fragile-looking inside--maybe I should start over and get a kit transformer too--I found these on the DSE catalogue... but I'm not sure if they're AC to DC--

You could use a DPDT relay to reverse the contacts to the DC plug.

Dave

 

[David L. Jones]

small relay with two sets of change over contacts
or use 4 transistors in a full bridge configuration

Thanks--but I need specific help--on circuit design and exactly which
components to buy. Ideally I would use a pre-bought transformer and
just add the polarity switching circuit at the dc end--that way it's
idiot-proof 240 volt-wise. Is this possible?

Yes.
Didn't you say you already had the 3V DC supply?
In that case you'll probably need another supply to power the timer.
Output of the timer drives a DPDT relay coil, DPDT relay contacts are
wired so the polarity gets swapped when the contact changes.
I failed ASCII ART at school.

It is possible to use plugpacks for both so there is no mains wiring
involved.

Dave

 

[Alf Katz]

Hi,

I bet you don't! Transformers do not put out DC.

Cheers,
Alf

 

[[email protected]]

Yes.
Didn't you say you already had the 3V DC supply?
In that case you'll probably need another supply to power the timer.
Output of the timer drives a DPDT relay coil, DPDT relay contacts are
wired so the polarity gets swapped when the contact changes.
I failed ASCII ART at school.

It is possible to use plugpacks for both so there is no mains wiring
involved.

Dave

OK thanks, yes, I have one 3V DC supply--so I need to buy another one
to power the timer. Can anyone draw me a wiring diagram or suggest a
site to find one on?
Thank you.

 

[The Real Andy]

OK thanks, yes, I have one 3V DC supply--so I need to buy another one
to power the timer. Can anyone draw me a wiring diagram or suggest a
site to find one on?
Thank you.

What are you trying to drive?

There should be tons of info on google. Do a search for h-bridge.

 

[[email protected]]

What are you trying to drive?

I want to switch a 3 VDC current from a plug in AC/DC transformer from positive to negative every 15 min. It's only for a hobby application. I thought of getting a kit for the timer--but don't know how to switch the polarity from positive to negative. If you can't help, that's

ok, I just thought I'd ask. Will search for h-bridge ...

 

[[email protected]]

[email protected] wrote:
Oh--I see--the H-bridge is for driving a motor--no, I don't need to
drive a motor, I just need the raw current. 15min positive--15 min
negative in a continuous cycle.

 

[[email protected]]

found this power supply at DSE: K3435
Features:
Can be used in a variety of ways as either a single or dual supply
Designed so that constructors can obtain many different voltages: +15V,
-15V, +/-15V, +18 to 22V, or less than 15V [I need 4.5V]
Power source required: Power adaptor or transformer (depending on
individual requirements)
Supplied with PCB and instructions only
Case optional (use H-2853)
PCB size:53mm x 71mm
Cat No. K3435

If anyone thinks this would work, good--just need to work out how to
switch it from positive to negative every 15min-- or maybe use 2 of
them through an AC to DC transformer--of course that may be easier
said than done...

 

[Kevin Martin]

:
: I bet you don't! Transformers do not put out DC.


they do if they are a plug pack transformer

most mobile phone chargers output "current limited" and "regulated" DC

you can buy one for a couple of bucks

you should open one and have a look, you might learn somthing!

Except there not transformers, they are power packs. Quite a difference
in fact.

--
Regards

Kevin Martin

To reply - delete what is "not required" (Abbrev) from my address.

 

[Guest]

There's something odd about this. The application (which he won't explain to
us) is fairly sophisticated yet the basic knowledge is about nil. Sorry
mate, not trying to be unhelpful but what exactly are you trying to do? Why
do you want to 'switch polarity'?

 

[Guest]

message : I bet you don't! Transformers do not put out DC.


they do if they are a plug pack transformer

Alf is right. No they absolutely DO NOT. NO transformer 'puts out DC'! Never
has done, never will do. You mean a plug pack power supply, which may
include a transformer and rectification circuitry. A pure transformer can
only ever put out AC.

most mobile phone chargers output "current limited" and "regulated" DC

you can buy one for a couple of bucks

Yes, right to a point, but they are NOT transformers per se!

:
: Cheers,
: Alf

cheers dickwad
:

Oh, that figures... Knowledge replaced by bad language. Usual replacement
when all fails. Good sign.

 

[[email protected]]

It's for a biomeditating device. Sorry I don't have a knowledge of
electronics. I saw a power supply kit at DSE. If I got 2 of them, set
them to 4.5V, made one positive and one negative, then used a timer kit
and a switch to alternate them, might that work?

power supply kit= K3435 Can be used in a variety of ways as either a
single or dual supply
· Designed so that constructors can obtain many different voltages:
+15V, -15V, +/-15V, +18 to 22V, or less than 15V [I would be setting it
to 4.5V]
thank you.

 

[Andy Wood]

It's for a biomeditating device. Sorry I don't have a knowledge of
electronics. I saw a power supply kit at DSE. If I got 2 of them, set
them to 4.5V, made one positive and one negative, then used a timer kit
and a switch to alternate them, might that work?

Sorry I don't have a knowledge of biomeditating (hey, who does?), so
I can't comment about whether the DSE power supply would be suitable.
How much current is required, and how close to 4.5V does it have to
be?

You don't need two power supplies to allow the polarity to be
reversed. Dave told you you could reverse the output with a DPDT relay
- perhaps you don't believe that? Look at the section on 'phase or
polarity reversal' here: http://www.1728.com/project2.htm

True, Dave did talk about two power supplies, but that was because you
first mentioned 3V DC and that might be too low for the timer
circuit..

This is starting to sound like a RGH thread.


Andy Wood
[email protected]

 

[Franc Zabkar]

Sorry I don't have a knowledge of biomeditating

You're in good company. Google doesn't know much either.

(hey, who does?)...

The bloke who started it all?
http://buryl.com/about.html

[Some of] Dr. Payne’s most important discoveries and writings
-------------------------------------------------------------

1. Discovered that the nearly regular cycles of international battles,
observed by previous researchers, is in phase with solar activity.

3. Conducted a 3 1/2 year experiment, with the assistance of many
participants. It consisted of 18 meditations/prayers for world peace
(or six meditations a year) to demonstrate that a sufficient number of
people meditating (several million) can apparently decrease solar
activity.

4. Rediscovered, by accident, (so often the case in science) a way to
detect and measure a rotational force, named the Biofield, around the
human body and other living things.

5. Validated Dr. Ron Hruby's breakthrough experiment, which
demonstrated that a small group of people, at a distance of ten miles,
could measurably alter the Biofield of a subject who was the object of
their distance healing.

9. Discovered a way to detect emanations from planets, which can alter
the taste of water. When this water is taken internally, it causes
psycho-physiological effects to occur.

12. Designed a simple electronic instrument to help synchronize brain
hemispheres to eliminate jet lag, and enhance telepathy. Made
instruments made for couples and groups to synchronize brain waves.

14. Author of 4 books on magnetism and its effects on living
organisms, BioMeditation: The scientific way to use the energy of your
mind ...

16. Currently writing a book on Fifth Dimensional Consciousness. Buryl
admits he doesn't understand it; that's why he's writing the book!

- Franc Zabkar

 

[David L. Jones]

found this power supply at DSE: K3435
Features:
Can be used in a variety of ways as either a single or dual supply
Designed so that constructors can obtain many different voltages: +15V,
-15V, +/-15V, +18 to 22V, or less than 15V [I need 4.5V]
Power source required: Power adaptor or transformer (depending on
individual requirements)
Supplied with PCB and instructions only
Case optional (use H-2853)
PCB size:53mm x 71mm
Cat No. K3435

If anyone thinks this would work, good--just need to work out how to
switch it from positive to negative every 15min-- or maybe use 2 of
them through an AC to DC transformer--of course that may be easier
said than done...

We have already told you how to do it, but I'll re-cap.

You need:
1) A power supply for your "device"
2) A timer that can switch on/off at the 15min interval you want.
Connect the output of the timer to the relay coil.
3) A DPDT relay. See the link Andy posted on how to wire it up to
reverse the polarity when the relay switches.
4) A second power supply (probably 12V or 5V) to power the timer and
relay. This is only required if the voltage of your other supply is not
suitable for this.

Dave

 

[[email protected]]

Thank you for your kind and patient help. I will look at the link. BTW,
The price of these things varies from between $250 and $3000 US--and
as to the power output, I'm not sure, but they normally run on D cell
batteries--but I had an old 'plug pack' ...

found this power supply at DSE: K3435
Features:
Can be used in a variety of ways as either a single or dual supply
Designed so that constructors can obtain many different voltages: +15V,
-15V, +/-15V, +18 to 22V, or less than 15V [I need 4.5V]
Power source required: Power adaptor or transformer (depending on
individual requirements)
Supplied with PCB and instructions only
Case optional (use H-2853)
PCB size:53mm x 71mm
Cat No. K3435

If anyone thinks this would work, good--just need to work out how to
switch it from positive to negative every 15min-- or maybe use 2 of
them through an AC to DC transformer--of course that may be easier
said than done...

We have already told you how to do it, but I'll re-cap.

You need:
1) A power supply for your "device"
2) A timer that can switch on/off at the 15min interval you want.
Connect the output of the timer to the relay coil.
3) A DPDT relay. See the link Andy posted on how to wire it up to
reverse the polarity when the relay switches.
4) A second power supply (probably 12V or 5V) to power the timer and
relay. This is only required if the voltage of your other supply is not
suitable for this.

Dave

 

[[email protected]]

Thanks for this most interesting reply--would like to follow this
amazing stuff up when I get a chance--have bookmarked it.

Sorry I don't have a knowledge of biomeditating

You're in good company. Google doesn't know much either.

(hey, who does?)...

The bloke who started it all?
http://buryl.com/about.html

[Some of] Dr. Payne's most important discoveries and writings
-------------------------------------------------------------

1. Discovered that the nearly regular cycles of international battles,
observed by previous researchers, is in phase with solar activity.

3. Conducted a 3 1/2 year experiment, with the assistance of many
participants. It consisted of 18 meditations/prayers for world peace
(or six meditations a year) to demonstrate that a sufficient number of
people meditating (several million) can apparently decrease solar
activity.

4. Rediscovered, by accident, (so often the case in science) a way to
detect and measure a rotational force, named the Biofield, around the
human body and other living things.

5. Validated Dr. Ron Hruby's breakthrough experiment, which
demonstrated that a small group of people, at a distance of ten miles,
could measurably alter the Biofield of a subject who was the object of
their distance healing.

9. Discovered a way to detect emanations from planets, which can alter
the taste of water. When this water is taken internally, it causes
psycho-physiological effects to occur.

12. Designed a simple electronic instrument to help synchronize brain
hemispheres to eliminate jet lag, and enhance telepathy. Made
instruments made for couples and groups to synchronize brain waves.

14. Author of 4 books on magnetism and its effects on living
organisms, BioMeditation: The scientific way to use the energy of your
mind ...

16. Currently writing a book on Fifth Dimensional Consciousness. Buryl
admits he doesn't understand it; that's why he's writing the book!

- Franc Zabkar