# Home Night Led Lamp

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this circuit lits 25 leds connected in serial using mains supply...

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## 12 Discussions

I'm not good at electric & electronic circuits, It's probably not the right place to ask, but just by curiosity: what's the purpose of the resistors and the capacitor?

Dear Joliveira,
To be more generic resisters act as current limiters and capacitors as a kind of DC filters (capacitors block DC current through them).

I think you can go on and add 25 more leds in the series but im not sure of the brightness its gonna offer... for more help on LEDs' you can refer this link http://www.allaboutcircuits.com/vol_3/chpt_3/12.html which covers most of the basics to deal with LEDs' their current ratting, peak reverse voltage, etc

Somebody needs to do an instructable on how you calculate the values for this type of circuit. With variables like number of LEDs, mains voltage and frequency, and current. If you stole this circuit or just fooled around until it worked, that's not you.

Jim, it is very basic stuff one can get from textbooks. The impedance of the capacitor is:
1/(2PiFC) = 1/(2 x 3.14 x 50 x 0.000000022) = 16k (impedance).
That renders a current of 14 mA (RMS) and 14x1.4 peak (20mA)
But since there is a phaseshift, the energy that is stored in the capacitor during half cycle will be reed during the other half. Therefore the capacitor, though functioning as an impedance, will hardly dissipate any energy.

So why the 22 Ohm.
It acts as a fuse should the capacitor fail.
It takes care of harmonics and other imperfections of the mains waveform
It buffers the LEDs against transients and the like.

Just as a safety note: The circuit is at full and half electrical mains potential.!!
So would be recommended that all wiring and components be safely isolated from end users.
the area from the Diode Bridge is at Half mains potential (in this case 115V).
The area before the Diode bridge is from half to full mains potential. And while
Anyone wishing to use this circuit will need to take this into account for their safety.
The risk current here will be in the order of 15mA RMS (~22mA Peak).. this is at the recognised human "Let Go Current..

Please take care with direct mains circuits.