Jeez this stuff drives me nuts. My understanding is that some transformers step it down to 12V AC and others to 12V DC. Half of the ads for transformers don't specify if the output voltage is AC or DC. I mean please, why isn't something that important specified?

Am I ignorant here? I mean there is of course a difference between 12V AC and 12V DC isn't there?

For example, this ad doesn't specify:

https://www.amazon.com/Watt-120V-Voltage-Ballast-KTET-75-1-SCP-DIM-HV-AL/dp/B004VW6Y4O/ref=sr_1_4?s=movies-tv&ie=UTF8&qid=1483222128&sr=8-4&keywords=12+volt+step+down+transformer

This one does:

https://www.amazon.com/150-Watt-Transformer-Halogen-BSET150/dp/B00905TLLU/ref=sr_1_1?s=movies-tv&ie=UTF8&qid=1483222851&sr=8-1&keywords=12+volt+step+down+transformer

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1986 300SDL, 362K
1984 300D, 138K

Try going to the manufacturer website for more info?

What you trying to do?

Internet shopping drives me nuts too.

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You don't need a weatherman to know which way the wind blows - Robert A. Zimmerman

Umm, one is a ballast resistor and the other is a transformer.

The 120V AC - 12V DC "transformer" is actually a rectifier since it doesn't actually transform anything. It merely isolates unwanted pulses and passes the selected currents.

The alternator on a car is an AC generator. The voltage is converted using diodes to only allow the "positive" flow of electrons.

How Power Supplies Turn AC into DC in Electronic Circuits - dummies

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“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now

Until we find out his application, he may want ac or dc.

https://www.youtube.com/watch?v=PiZHNw1MtzI

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1987 560SL
85,000 miles

The alternating current changes the magnetic field and is a requirement for a normal transformer to work. Alternating current in and alternating current out.


To get direct current the output of any transformer must be processed.


Now to add some clarity. There are all kinds of items available that can do whatever you want to do. Direct current to direct current. Alternating current to direct current. Direct current to alternating current.


With a lot of items today being really voltage specific you may also need to seek out a device that also gives a regulated output. Or you can damage things.


Fortunatly most of the simple needs can be serviced quite cheap with Chinese built devices on ebay.


There are several things you must know before ordering though. The expected load the device services is really an important one. Plus of course both the voltage output and input required for the device.


I keep an assortment of alternating current to direct regulated voltage units on hand. They are less than 10.00 each delivered for the lower current ones and fully regulated and protected internally.


I was thinking just the other day that I grew up in the more mechanical world than exists today. The transformer is far from obsolete but has been passed over in your application to some degree. They have always had a problem inherent with them. The amount of load determines the output voltage. For example. If you purchased a 110 to 12 volt transformer. with very light loading 15-17 volts output may be present.


What is interesting in many ways a totally uneducated English man for all practical purposes discovered most things that enabled what I grew up with to exist. Then sometime in the 1960s an electronic revolution started and seems to be continuing.


Things like cellphones than are taken for granted today are really pretty complex devices.


Back in the day when I was sitting at my bench repairing the early transistorized equipment I could not have forcast the amount of evolution that has occurred. It was so easy back then I could repair about four items an hour at times.


What is equally amazing with no electronic knowledge other than how to use a meter today. Many people can repair their flat screen televisions. At the same time periodically I open up other current electronic devices occasionally and for all practical purposes they are not repairable.

I dread getting into discussions about electronics here, but I'll make it very simple:

A transformer is ALWAYS AC to AC. ALWAYS. Anything that produces 12v dc output is properly referred to as a power supply, and usually is built from a transformer and a rectifier, or it can be all solid state.

Thank you. I didn't want to get into the explanation of the difference. It is like trying to describe the difference between a "motor" and an "engine".

And the reverse (DC to AC) is an inverter.

__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now

Just to pass along some buying info......

I needed a 12vdc power supply for my work bench. My wife thought that with the kind of money I make I could do better than using an old 12v battery that I kept on a charger.

But I had the charger and someone gave me the battery. Yeah, I'm cheap.

So I went shopping on Ebay for a 12vdc power supply. I found that those that put out some amps, like 30 or so, cost a great deal. But those that put out 30 amps or so and didn't have a meter or two on them went for less than $20.

I have a voltmeter. I can check the output before I hook up a radio or a clock to test. I don't need a meter on the unit.

So if you choose this route then look for a power supply without a meter and buy it cheap. Mine is almost twenty years old, gets used at least twice a week, and works great.

Idle - am I missing something? For years when I need DC, say to run the little compressor for a tire, I just hook up my Sears charger and put the alligator clips on the two poles of the compressor's cigarette lighter plug - instead of plugging the little compressor into the cigarette lighter itself.

Are you saying you bought a battery for this?

Sounds like he needs clean DC power and a charger wont provide that.

Some reclaimed computer tower power supplies can be used but not at the amperage level he seems to need.

If we knew what you wished to power. I think we could locate a cheap enough device for you. Unless it is something with a really heavy draw. Also it would give an indication of the refinement of the direct current needed. Not all applications are equal.


Old free or almost free computer power supplies as mentioned are many times all that is required. As power supplies go they are very good if useful for your needs.