I made a transformarless power supply with capacitor. When i connect it on ac, it light the leds. But after some second the 100ohm resistor and 470uf capacitor get too hot. Its too hot that i could not touch it then. What's the problem . Pls help me.
Answer
- With 12Vdc drawn from 230Vac, you have a current-limit by 100Ω and 2.2uF @ 100Hz = -j800 Ohms for an apparent current of ~170 mA .
- with 230mA rms thru 100 Ohms the power dissipation is I^2R-Pd=5.3W exceeding its rating and operating a finger burning max temps of 150'C+
Conclusion
You must use an e-Cap rated for > .4A ripple current with low ESR for safety or reasonable life.
- Don't use Chinese Caps with no specs ( Japanese are far better)
- example Rubycon Manufacturer Part Number 25ZLH470MEFC10X12.5 730 mA ripple @ 120Hz
Proof with SIM 
- Always derate power resistors at least 33% and pre 50% - so use a 10W resistor or add another 100 OHm 5W in series. which only reduces overall current by 5mA.
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