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12 volt DC to 9 Volt AC

E

Eric

Jan 1, 1970
0
OK, did a search, didnt come up with anything. I'm wondering how
hard/easy it will be to make something that can convert 12 volt DC to
9 Volt AC. It needs to be fairly regulated and clean, as its for a
piece of audio equipment, but not super sensitive like a computer.

What im doing is trying to use an Alesis Nanoverb in my car. It has a
'wall wart' power supply of 120 volt in and 9 volt AC out. Not sure
what frequency AC out. Im assuming 60 hz. I dont really think using
a 12 volt to 120 volt setup up inverter will work that well. Maybe
thres another component that has 12 volt DC input... hmm. Im pretty
good at basic electronic projects. Not sure about this one, so thats
why I'm asking here. Any thoughts?
 
I

Ian Stirling

Jan 1, 1970
0
Eric said:
OK, did a search, didnt come up with anything. I'm wondering how
hard/easy it will be to make something that can convert 12 volt DC to
9 Volt AC. It needs to be fairly regulated and clean, as its for a
piece of audio equipment, but not super sensitive like a computer.

What im doing is trying to use an Alesis Nanoverb in my car. It has a
'wall wart' power supply of 120 volt in and 9 volt AC out. Not sure
what frequency AC out. Im assuming 60 hz. I dont really think using
a 12 volt to 120 volt setup up inverter will work that well. Maybe
thres another component that has 12 volt DC input... hmm. Im pretty
good at basic electronic projects. Not sure about this one, so thats
why I'm asking here. Any thoughts?

It will almost certainly do no damage to connect it directly to the
car battery.
9V AC at peak is some 13V or so.
On a +10% AC line, 14.5V.

It will almost certainly work just fine.
What current is it supposed to draw, and what is it?
Does it have any sort of motor?
 
J

John Woodgate

Jan 1, 1970
0
(in said:
OK, did a search, didnt come up with anything. I'm wondering how
hard/easy it will be to make something that can convert 12 volt DC to
9 Volt AC. It needs to be fairly regulated and clean, as its for a
piece of audio equipment, but not super sensitive like a computer.

What im doing is trying to use an Alesis Nanoverb in my car. It has a
'wall wart' power supply of 120 volt in and 9 volt AC out. Not sure
what frequency AC out. Im assuming 60 hz. I dont really think using
a 12 volt to 120 volt setup up inverter will work that well. Maybe
thres another component that has 12 volt DC input... hmm. Im pretty
good at basic electronic projects. Not sure about this one, so thats
why I'm asking here. Any thoughts?

You probably don't need to put in 9 V AC. The unit obviously has a
rectifier on board, and you can feed that with DC of either polarity.
The only way it won't work is if the unit has two rectifiers, one
producing positive DC and the other producing negative DC.

Since the peak voltage of 9 V r.m.s. AC is 12.7 V, you appear to be able
to just feed your 12 V vehicle supply to the unit, even though that is
about 13.8 V when the battery is being charged. BUT that 12 V supply has
lots of nasty transients on it and your unit won't be protected against
those. I suggest you put about 10 ohms in series with the feed from the
vehicle and a 12 V zener diode across the input to your unit.
 
J

j.b. miller

Jan 1, 1970
0
Ian makes the ASSumption that the device takes the AC and converts it to
ONLY one value of positive DC.
WRONG and very,very dangerous ASSumption.
Without schematics, no one KNOWS what's going on. Early modems converted the
AC into 2 or 3 DC levels(+12,+5,-12) for true RS-232 use.
I have a piece of proprietary equipment that does the same(+60,+5,-60).
So either open up the device or get schematics, just plugging in and turning
it on could be a very costly mistake.

jay
 
S

Spehro Pefhany

Jan 1, 1970
0
Ian makes the ASSumption that the device takes the AC and converts it to
ONLY one value of positive DC.
WRONG and very,very dangerous ASSumption.
Without schematics, no one KNOWS what's going on. Early modems converted the
AC into 2 or 3 DC levels(+12,+5,-12) for true RS-232 use.
I have a piece of proprietary equipment that does the same(+60,+5,-60).
So either open up the device or get schematics, just plugging in and turning
it on could be a very costly mistake.

jay

The wall wart also provides galvanic isolation. Really, just go buy a
cheap inverter and be done with it.

Best regards,
Spehro Pefhany
 
R

Roger Hamlett

Jan 1, 1970
0
j.b. miller said:
Ian makes the ASSumption that the device takes the AC and converts it to
ONLY one value of positive DC.
WRONG and very,very dangerous ASSumption.
Without schematics, no one KNOWS what's going on. Early modems converted the
AC into 2 or 3 DC levels(+12,+5,-12) for true RS-232 use.
I have a piece of proprietary equipment that does the same(+60,+5,-60).
So either open up the device or get schematics, just plugging in and turning
it on could be a very costly mistake.
Also, even if the system is wired as Ian assumes, if it is using 'full
wave', rather than half wave rectification, the average current through the
pair of diodes 'in use' when operating off DC, is higher than when running
on AC, which can again cause problems. Basic rule of thumb, is if you don't
know what is going on inside a unit, 'assume the worst'...

Best Wishes
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that j.b. miller
Ian makes the ASSumption that the device takes the AC and converts it to
ONLY one value of positive DC.
WRONG and very,very dangerous ASSumption.
Without schematics, no one KNOWS what's going on. Early modems converted the
AC into 2 or 3 DC levels(+12,+5,-12) for true RS-232 use.


This is a piece of audio gear. The most complication is that it has +
and - rails.
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog
DOTyou.knowwhat> wrote (in said:
The wall wart also provides galvanic isolation. Really, just go buy a
cheap inverter and be done with it.

Why would you need galvanic isolation for a bit of audio kit in a car?
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Roger Hamlett <rogerspamignored@tt
elmah.demon.co.uk> wrote (in said:
Also, even if the system is wired as Ian assumes, if it is using 'full
wave', rather than half wave rectification, the average current through the
pair of diodes 'in use' when operating off DC, is higher than when running
on AC, which can again cause problems. Basic rule of thumb, is if you don't
know what is going on inside a unit, 'assume the worst'...
This is a piece of audio processing gear. If it takes 100 mA that will
be tops. Risk to diodes - zilch.
 
S

Spehro Pefhany

Jan 1, 1970
0
I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog


Why would you need galvanic isolation for a bit of audio kit in a car?


Signal ground is connected to chassis ground at the audio input and
output jacks, so there's the possibility of ground loops with the rest
of the system.

I also think the likelyhood is high that they are generating +/-
rails, otherwise they would probably have designed in a DC-output
wall-wart.

Best regards,
Spehro Pefhany
 
I

Ian Stirling

Jan 1, 1970
0
John Woodgate said:
I read in sci.electronics.design that Roger Hamlett <rogerspamignored@tt

This is a piece of audio processing gear. If it takes 100 mA that will
be tops. Risk to diodes - zilch.

Plus, the RMS current through the diodes will probably be smaller.
Instead of conducting 1A for 10% of the time, any bridge diodes will
conduct 200ma continuously.
It's probable that they'd run cooler.
 
E

Eric

Jan 1, 1970
0
Ian Stirling said:
It will almost certainly do no damage to connect it directly to the
car battery.
9V AC at peak is some 13V or so.
On a +10% AC line, 14.5V.

It will almost certainly work just fine.
What current is it supposed to draw, and what is it?
Does it have any sort of motor?

To answer your questions- it is a signal processor for audio. It adds
reverb, delay, chorus etc. It draws probably less then 1 amp. It is
not a power amplifier and no it does not have any motor.

So you're saying I can plug 12 volt DC directly into the terminal that
calls for 9 volts AC?
 
T

Tim Mitchell

Jan 1, 1970
0
Eric said:
To answer your questions- it is a signal processor for audio. It adds
reverb, delay, chorus etc. It draws probably less then 1 amp. It is
not a power amplifier and no it does not have any motor.

So you're saying I can plug 12 volt DC directly into the terminal that
calls for 9 volts AC?

No, as others have said, it uses the AC to generate + and - rails. DC
won't work. I used to own one and occasionally mixed up its AC power
supply unit with DC ones.
 
I

Ian Stirling

Jan 1, 1970
0
Eric said:
To answer your questions- it is a signal processor for audio. It adds
reverb, delay, chorus etc. It draws probably less then 1 amp. It is
not a power amplifier and no it does not have any motor.

So you're saying I can plug 12 volt DC directly into the terminal that
calls for 9 volts AC?

I was saying it probably won't damage it, which is not quite the same thing.
However, as others have raised, you can't safely plug it into other car
audio stuff, as the grounding would be wrong.

However, I see that someone actually has owned one, and tried this without
it working, so no.
An inverter looks like your easiest option.
 
T

Tam/WB2TT

Jan 1, 1970
0
Go open up your Nanoverb, and see what it does with the 9VAC. If the 9V goes
into a diode rectifier, and nowhere else, you can power it from 9 - 10 VDC
as well, provided the case is negative (Like from a 7810).

Tam
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog
I also think the likelyhood is high that they are generating +/-
rails, otherwise they would probably have designed in a DC-output
wall-wart.

You may well be right. But using an AC wall-wart makes some safety
compliance issues simpler.
 
J

John Woodgate

Jan 1, 1970
0
(in said:
So you're saying I can plug 12 volt DC directly into the terminal that
calls for 9 volts AC?

It's possible. It MIGHT not work (if the unit generates + and - rails
internally), in which case disconnect at once. But you are *unlikely* to
cause any damage. The best thing to do would be to try to get
information form the manufacturer on the subject.
 
S

Spehro Pefhany

Jan 1, 1970
0
I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog


You may well be right. But using an AC wall-wart makes some safety
compliance issues simpler.

Interesting. Could you expand on that a bit?

Best regards,
Spehro Pefhany
 
T

Tam/WB2TT

Jan 1, 1970
0
As others have mentioned, make sure no (-) voltage is generated. They may
have one side of the AC grounded, and +/- half wave rectifiers, or some
other arrangement. They may even use a voltage doubler. You would have to
run the thing off the AC and see if there are any negative voltages with
respect to ground, or any voltages around 20 or so.

Tam
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog
DOTyou.knowwhat> wrote (in said:
Interesting. Could you expand on that a bit?

I'm thinking back to a project several years ago, involving CSA
certification. AC-output wall-warts were treated much less stringently
than DC output ones. I suppose the justification was that AC output
devices were just a 'transformer in a box', whereas DC output devices
would have additional electronics of unknown extent and raise unknown
safety issues.

I don't know whether the CSA requirements are still similar, nor whether
current UL requirements are similar or not.
 
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