Electric shock through simple series capacitor mains power supply

[Willen]

Hi,
Look at the attached sample circuit (from the internet) first below. Many cheap devices are being controlled by such power supply like some mains LED lamps, simple colorful flashing LED lamps, torch lights etc. As my experience, in a tourch the power supply was charging its 6V battery of a tourch. I was touching battery's poles but during turning ON and OFF the switch was making little loud sparking and noise (actually all the such power supply makes sparking and noise always during switching ON and OFF or during plugging IN or OUT). And exactly as sparking, I was feeling shocks in my fingers! What and how was that shocking?

 

[Nigel Goodwin]

As the entire circuit is live to the mains, then you were getting mains shocks - as you would expect.

 

[Willen]

Ops, then what happels if the LEDs or some IC are getting power through the circuit? Probably the load circuit may not be alive more than few months, specially in the place like mine where mains power failure is more than 50 times every day.

 

[JimB]

How many times does it have to be stated here and on other electronic forums, that transformerless mains power supplies are dangerous.

Such power supplies must only be used when there is NO POSSIBILITY of touching the wiring or components.

JimB

 

[Willen]

I am not making these supplies but many cheap devices I bought have such power supply. So I am worrying about them. If their output is very rough and not stable, it's dangerous to human but also dangerous to its load circuit/device? Probably the device powered by such supply won't be working more. So feeling like to add some components before and after the power supply like mains filter etc. What you prefer to add specially before the power supply as mains filter? (I have fuse, NTC, power resistors and inductors )

 

[schmitt trigger]

You mentioned it correctly: cheap devices.

The only reason that transformerless supplies exist is the low cost. They are dangerous, they are unreliable, they have poor performance, but hey! who can't resist a bargain?