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HELP!! TRANSFORMLESS power supply

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Boncuk

New Member
Hi,

I'm afraid you will have to use a transformer.

2A of current flow gained by a capacitor (used as AC resistor) makes that kind of power source unaffordable, because of the huge capacitor which will be involved.

Boncuk
 

SPDCHK

Member
Simply Google for it, but I'm afraid the current requirements will not be met.

These types of power supplies usually supplies in the range of 50mA. More than that and the components becomes too big as Boncuk said.
 

crutschow

Well-Known Member
Most Helpful Member
You could build a line powered switching regulator (which does require an inductor) but it would be dangerous, since it wouldn't be isolated from the line.
 
There have been a lot of previous posts for transformerless power supplies, most including dire safety warnings cuz it's dangerous. Check out this post and this website.

But I think 2A may be a dream too far.

Originally Posted by Crutshow
You could build a line powered switching regulator (which does require an inductor) but it would be dangerous, since it wouldn't be isolated from the line.
That sounds interesting (dangerous, but interesting) - is there a schematic online somewhere to look at?
 
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tcmtech

Banned
Most Helpful Member
What are you powering that takes two amps at 12 volts?

A capacitive power supply can easily do 2 amps.
You guys must not work with AC motor run/ power factor correction capacitors much. You would need only need a 25 uf 370 volt AC capacitor.
The modern ones of that value are about the size of a camera film can.

Heres a basic schematic of what you would need.
 

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Sceadwian

Banned
And once again, if the capacitor fails short circuit the entire projects explodes into a ball of plasma, and anyone touching something electrically connected to the device will have their heart stopped. The size benefit is negligible. Weight can't be a problem as it's a mains powered device. There's no point from the begging for it. If you want small/light still use a switch mode supply which has a tiny transformer.
 
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desmondlai

New Member
i use it for my router adapter that need 3.3v 2A
i have 2 part of the circuit 1st part is the rectifier part and 2nd part is my lm317 regulator part
 

tcmtech

Banned
Most Helpful Member
if the capacitor fails short circuit the entire projects explodes into a ball of plasma, and anyone touching something electrically connected to the device will have their heart stopped.
Modern AC capacitors all have internal fusing standard. Most have well over 100K hours life expectancies at room temps too.;)

Sometimes I just like to give people people what they ask for. No complicated lectures about safety or anything! :eek::D

Heres a knife. It great for many uses. One end is sharp, you figure it out.
Your bleeding! I guess you just figured out which end is the sharp one!:D

At least this shows my posts are still being read!:p
 

goofeedad

New Member
What are you powering that takes two amps at 12 volts?

A capacitive power supply can easily do 2 amps.
You guys must not work with AC motor run/ power factor correction capacitors much. You would need only need a 25 uf 370 volt AC capacitor.
The modern ones of that value are about the size of a camera film can.

Heres a basic schematic of what you would need.
Whoa! Did I miss something? I have been trying to make a circuit like the one you showed but, EVERYONE says don't do it, it's dangerous. I need a circuit like this one that changes 120VAC to 36VAC or 48VDC at 0.66amps, if I bypass the internal bridge rectifier. It looks like I could build several of these to run my seperate driver boards. I believe I could put these circuits in a seperate box to keep everyone safe.
 

Boncuk

New Member
There was a sufficient number of warnings in every reply.

Here is another circuit which might suit your needs after minor modifications.

Boncuk
 

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goofeedad

New Member
There was a sufficient number of warnings in every reply.

Here is another circuit which might suit your needs after minor modifications.

Bink
I agree with you. You have always (that I've read anyway) given sufficient warnings to CYA (cover your A**). That wasn't my concern.

Thanks for the additional circuit diagram but, I guess it's a little too advanced for me. I don't understand some of the symbols.

Right now I'm having some transformer problems that I would like to bypass, so I'm reconcidering the switching supply idea. Just need 36VAC or 48VDC supply at .66A or better, there will be 4 drivers each requiring 0.66A.
 

crutschow

Well-Known Member
Most Helpful Member
Note that reducing the voltage with a series capacitor normally requires a shunt regulator for voltage regulation. Thus it always draws maximum current from the line and is only efficient at near its maximum rated load.
 

tcmtech

Banned
Most Helpful Member
Whoa! Did I miss something? I have been trying to make a circuit like the one you showed but, EVERYONE says don't do it, it's dangerous. I need a circuit like this one that changes 120VAC to 36VAC or 48VDC at 0.66amps, if I bypass the internal bridge rectifier. It looks like I could build several of these to run my seperate driver boards. I believe I could put these circuits in a seperate box to keep everyone safe.
I am feeling generous today! here you go!
120 VAC to 40 - 48 VDC at .75 Amps peak.
Dont hurt yourself, line powered, use caution, Blah, Blah, Blah.
You were warned!;):D
 

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goofeedad

New Member
I am feeling generous today! here you go!
120 VAC to 40 - 48 VDC at .75 Amps peak.
Dont hurt yourself, line powered, use caution, Blah, Blah, Blah.
You were warned!;):D

Thank you and all your generousity! I will use caution. Ok, now that I have it, I feel a sense of doom. Other than keeping this circuit dry and keeping all hands off, do I really need to keep any other precautions. For example fuses, isolators, insulation, etc...

I feel like I've been given Padoras box and I don't want to let any demons out that might bite me or others.

Thanks.
 

tcmtech

Banned
Most Helpful Member
Depends on who you ask! A one amp fuse and a GFI should cover the basics. Put it in a weather tight box if its possibly going to get wet.

For a three wire cord with built in GFI on the cheap stop by garage sales or thrift stores and pick up a modern hair dryer for a couple of dollars. The cord has that built in GFI all wired up for you!

I often buy outdoor circuit breaker boxes for things that need to work in damp or wet environments. Mount the heat sink on the side some place and use silicone sealer to make it leak proof and your basically weather proof and tamper resistant and
the fuse and GFI cover everything else as far as the NEC code rules are concerned.

Pandora be dammed! Go have some almost educational fun! :D
 
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goofeedad

New Member
Depends on who you ask! A one amp fuse and a GFI should cover the basics. Put it in a weather tight box if its possibly going to get wet.

For a three wire cord with built in GFI on the cheap stop by garage sales or thrift stores and pick up a modern hair dryer for a couple of dollars. The cord has that built in GFI all wired up for you!

I often buy outdoor circuit breaker boxes for things that need to work in damp or wet environments. Mount the heat sink on the side some place and use silicone sealer to make it leak proof and your basically weather proof and tamper resistant and
the fuse and GFI cover everything else as far as the NEC code rules are concerned.

Pandora be dammed! Go have some almost educational fun! :D
Thank you. Please indulge me and let me please ask something else. The variability between 40v and 48V, is that dependant on R2 or the zener (am I suppose to use 4 1W zeners if I can't get a 4W) and (as if I wasn't allreay too anoying) why is R1 optional?

Again, THANKS!
 
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