, wat s goin on in here ??? 
i checked my first schematic several times , and i didn t understand where the problem is ! , if any body saw my first schematic can explain it easier for me to understand what s wrong in that plzzz ?????
u r posting and posting and just say not to use a transformerless supply ! can any body tell me why ?? why i cann t ????
and i m still looking for a transformerless circuit ! if any body can help me with that i ll be so gratefull thanks all .
Ahmad_tbp said:
yes indeed
www.google.com
find switched power supply
try it for hi-voltage either.
i advise you to get to know them and understand them.
like i did
you should be able to get or make a really small tansformer for this kind of psu.
just tear apart an 'old' cell phone charger... the smallest one you could get. there you will see how small things can be.
i uzed one of those psu for a digital headfone equalizer + headfone amp. but... i found a full made one ^^
do as i do. loose LOTs of time learning this little things... it may be uzefull later.
Ahmad_tbp said:
i checked my first schematic several times , and i didn t understand where the problem is ! , if any body saw my first schematic can explain it easier for me to understand what s wrong in that plzzz ?????
u r posting and posting and just say not to use a transformerless supply ! can any body tell me why ?? why i cann t ????
thanks all .
You're unlikely to find answers to such questions, the reason people may be saying not to do it transformerless is because it is unsafe to work off the mains directly, especially when you're less than a professional. So because of the danger, and your need to be asking for a schematic because of a lack of understanding, they will not be willing to help you put yourself in danger, giving you such a schematic would be a green light towards endangering yourself.
As firefart pointed out the transformer that you'd need in a smps can be very small and cost effective, so there's really little reason not to use one.
Also as firefart pointed out, your best bet is to increase your level of understanding through research so that eventually you won't have to be asking for schematics and will have the ability to work safely.
Regards
Chris
Many switch mode power supplies have an isolation transformer inside them. It may be small due to the high operating frequency. There are switchmode supplies (the classic boost or buck designs) that offer NO isolation and do NOT belong in any equipment with exposed metal pieces that are connected to the internal circuitry.
Basically it comes down to this. If there is ANY path from the power lines anything that can be touched by the user you can be FRIED! This is electrically the same as standing barefoot in a puddle of water and sticking a metal fork in a light socket while holding it tightly. A transformer has no electrical connection between the primary and secondary. It relies on magnetic coupling to transfer the energy.
If you don't understand these concepts, please find someone to help you who does. Getting fried by 230 volts really doesn't sound like much fun to me.
Hi,
The keyword here is "galvanic isolation". Both transformers and opto-couplers/isolators accomplish this.
You're quoting tubelab, but he seems to be aware of all this already, so there's little point in debating with him.
"have you wonder why a PC PSU does not blow away fuses and etc when its connected to other systems ?
they have total insulation. "
Really? What of the earth line? This is a very common problem area when it comes to soundcards and ground loops!
When you have a common connection (such as with the ground) it by no means qualifies as having "total insulation".
The rails and control circuitry are no doubt galvanically isolated, at least until something shorts to ground, then you'll have your blown fuse
The keyword here is "galvanic isolation". Both transformers and opto-couplers/isolators accomplish this.
You're quoting tubelab, but he seems to be aware of all this already, so there's little point in debating with him.
"have you wonder why a PC PSU does not blow away fuses and etc when its connected to other systems ?
they have total insulation. "
Really? What of the earth line? This is a very common problem area when it comes to soundcards and ground loops!
When you have a common connection (such as with the ground) it by no means qualifies as having "total insulation".
The rails and control circuitry are no doubt galvanically isolated, at least until something shorts to ground, then you'll have your blown fuse
if the transformerless schematic had been left there, it would only be a matter of time before someone copy&pasted it, without reading the thread and without text, onto
www.1000awesometubedesigns.com
www.1000awesometubedesigns.com
I guess he is allowed an opinion the same as I am.
The missed point here is that people do not, will not learn when someone tells them you cannot make this because I said so. This attitude does not teach anyone anything.
Any power supply is dangerous period. I believe the main objection seems to be that of exposure to 120volts or 220v or what ever the hell your mains voltage is. Is there any less exposure to say a 250volt DC supply? A misplaced hand or finger will still fry your *** won't it?
Want isolation? Throw a damn 600-600 transformer in there.
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