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

use the 555 to switch a small relay with two sets of change over contacts or use 4 transistors in a full bridge configuration

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. : : >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.) : 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. :

I want to change the polarity from positive to negative every 15 minutes in a continuous cycle.

K2813--Discovery Series Kit Multi 555 Timer for $20.

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--

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 snipped-for-privacy@trap.ozemail.com.au

I want to change the polarity from positive to negative every 15 minutes in a continuous cycle.

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.

K2813--Discovery Series Kit Multi 555 Timer for $20.

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

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 :)

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?

David L. J> > Hi,

and I want to change the polarity from positive to negative every 15 minutes in a continuous cycle.

K2813--Discovery Series Kit Multi 555 Timer for $20.

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--

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 :)

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

Cheers, Alf

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.

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!

: : Cheers, : Alf

cheers dickwad : :

What are you trying to drive?

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

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 ...

snipped-for-privacy@cool.com.au 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.

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

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 any> snipped-for-privacy@cool.com.au wrote:

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

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.

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'?

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.

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

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

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=3D K3435 Can be used in a variety of ways as either a single or dual supply =B7 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.

snipped-for-privacy@tpg.com.au wrote:

ver

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:

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 snipped-for-privacy@trap.ozemail.com.au

On Tue, 25 Jul 2006 23:18:27 GMT, snipped-for-privacy@trap.ozemail.com.au (Andy Wood) put finger to keyboard and composed:

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

The bloke who started it all?

[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.

1. 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.

2. 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.

1. 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.

2. 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.

1. 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.

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

1. 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

--
Please remove one 'i' from my address when replying by email.

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 :)