### Author Topic: 9V to 6v ac adapter  (Read 2707 times)

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#### vipulan12

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##### 9V to 6v ac adapter
« on: July 15, 2013, 08:51:26 PM »
how can you convert a 9v AC adapter to a 6V ac adapter?
would i need to use a regulator?
what are the calculations i should consider?

#### waltr

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##### Re: 9V to 6v ac adapter
« Reply #1 on: July 15, 2013, 09:25:32 PM »
In general just run the 9VDC through a 6V regulator. An LM7806 is the easiest to use.
http://www.fairchildsemi.com/pf/LM/LM7806.html
Provided you don't need more than 1A of current.

Next option is to use an LM317, an adjustable linear regulator. This take a few more parts to set the output Voltage but may be easier to find than the LM7806.
http://www.mouser.com/Search/Refine.aspx?Keyword=LM317&gclid=CInmveyHs7gCFY2Z4AodAjcA1w

The calcs needed is the heat dissapated by the regulator which is: heat (Watts) = (Vin - Vout) * current (Amps).
For the LM317 you need to calculate the resistor but the info for this is in the data sheet.

How much current does your 9V adapter output?
How much current does your circuit require?

#### newInRobotics

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##### Re: 9V to 6v ac adapter
« Reply #2 on: July 16, 2013, 12:29:09 AM »
In general just run the 9VDC through a 6V regulator. An LM7806 is the easiest to use.
OP asked how to convert 9V AC adapter to 6V AC adapter. Your suggestion might cause some undesirable outcome
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#### jwatte

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##### Re: 9V to 6v ac adapter
« Reply #3 on: July 16, 2013, 09:51:57 AM »
Assuming you actually have a 9V AC output, and you want a 6V AC supply, then you should use a power transformer with a 3:2 winding ratio. Supply 9V AC to the "3" side, receive 6V AC on the "2" side. Magic! :-)

Btw: Some people call anything that plugs into the wall an "AC" adapter, because it adapts the "AC" from the wall, even if it generates DC. If the supply generates 9V DC, and you want 6V DC, then the best way to do that is with a switching DC DC converter (step-down converter, typically "buck" converter.) Pololu sells some decent ones. Hobby stores also sell them as "UBECs."

#### johnwarfin

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##### Re: 9V to 6v ac adapter
« Reply #4 on: July 16, 2013, 10:34:35 AM »

http://www.societyofrobots.com/robotforum/index.php?topic=17051.0

are you having fun or just lonely?

#### vipulan12

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##### Re: 9V to 6v ac adapter
« Reply #5 on: July 16, 2013, 01:56:16 PM »
so could either create a transformer or buy a 6v regulator
i guess the regulator should be the better choice since i would to convert the dc back to ac to use the transformer than back to dc
thanks

the ac adapter provides 210 ma and i think 1 A should be enough
« Last Edit: July 16, 2013, 01:59:10 PM by vipulan12 »

#### johnwarfin

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##### Re: 9V to 6v ac adapter
« Reply #6 on: July 16, 2013, 04:20:44 PM »
dc to ac then back to dc makes little sense. you need to clearly describe your goals and applications to make more sense and get better help.

also note that common linear regulators like 7806 (you can make one with a 7805 and diode) will not supply anything close to 1a w/o a heat sink. a BIG one. even 210ma is borderline w/o one. it will run hot. you need to use a dc-dc converter. assuming there is a real application here which is not clear.

#### waltr

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##### Re: 9V to 6v ac adapter
« Reply #7 on: July 16, 2013, 05:29:32 PM »
In general just run the 9VDC through a 6V regulator. An LM7806 is the easiest to use.
OP asked how to convert 9V AC adapter to 6V AC adapter. Your suggestion might cause some undesirable outcome

Beginner question are confusing.
I took it to mean an AC to DC adapter (wall wart) with 9V output (DC). These are very common so went with that. 9VAC output adapters are less common these days.
Guess I should have had the OP explain exactly what he/she has first.

#### jwatte

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##### Re: 9V to 6v ac adapter
« Reply #8 on: July 16, 2013, 10:05:03 PM »
so could either create a transformer or buy a 6v regulator

No.

If you are talking about an AC adapter that outputs AC voltage, then you have to use a transformer; a regulator will not work.
If you are talking about a wall wart that actually outputs DC voltage, then you have to use a regulator, either linear (7806, LM350, etc) or switching (something from http://www.pololu.com/catalog/category/131 perhaps.)

Transformers are used to change the voltage of an alternating current signal.
Regulators are used to change te voltage of a direct current signal.
You need to know which one it is you're dealing with.

#### vipulan12

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##### Re: 9V to 6v ac adapter
« Reply #9 on: July 17, 2013, 03:09:14 PM »
sorry for the confusion, i meant i wouldn't want to use a transformer since i would have to convert the DC back to AC then to DC again,the regulator is the better choice

#### waltr

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##### Re: 9V to 6v ac adapter
« Reply #10 on: July 17, 2013, 07:36:08 PM »
Quote
If you are talking about an AC adapter that outputs AC voltage, then you have to use a transformer; a regulator will not work.
This is not completely true.
It would be easier (and is more common) to rectify the 9VAV to DC, Filter with a large cap, then regulate to 6VDC with either of the linear regulator I listed in post #2.

#### jwatte

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##### Re: 9V to 6v ac adapter
« Reply #11 on: July 17, 2013, 11:06:09 PM »
Quote
It would be easier (and is more common) to rectify the 9VAV to DC, Filter with a large cap, then regulate to 6VDC with either of the linear regulator I listed in post #2.

You are trying to accomplish something else with that statement. You are trying to *both* do AC-DC conversion, and voltage regulation.

If you have 9V AC out, and want 6V AC out, then a linear regulator will not work. At all. If you read the original question literally, that's actually what's being asked.

#### vipulan12

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##### Re: 9V to 6v ac adapter
« Reply #12 on: July 18, 2013, 11:52:23 AM »
no i want 6v DC out

#### jkerns

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