Transformelesss power supplies are useful lighting LEDs.Before I go any further I would like to point out that this is the most dangerous circuit I've ever made so far.It is definitely not for amateurs.The shock risk is very high because of the design of this circuit.For more info on this read the Danger section of this post.
I've reproduced the circuit found in this site to power a 10watt LED.
Some of the specs
input power 240 AC/50hz
output 15 volts DC
driving a 10 watt LED that draws 220 milliamps
output current 1.2 amps according to the designer of this circuit
Here are the parts I've used.
two 2uF/250Volts film capacitors in parallel (the output depends on this cap-more caps in parallel more amps.Higher voltage rating-higher DC output)
10M resistor in parallel with the caps above.This resistor acts as a bleeder.It discharges-it bleeds- the caps after you turn the circuit off.Otherwise they can remain charged for a very long time making them a shock hazzard.
four 6 amp diodes (four amp or more are needed-double the outpout amperage which is 2 amps) as a rectifier bridge.This rectifies -turns the AC to DC.
3700uf/16volts electrolytic capacitor (I should have used higher voltage rating but that's what I had)
one 15volt zener diode to limit DC output.This one filters the ripple on the rectifier bridge output making the DC wave smoother
one 100ohm/10watt resistor in series with one of the mains lead to protect the circuit
one 10ohm/5watt resistor
5Amp fuse-always use a fuse.If something goes wrong- and I wish it won't-some of excessive current will go to the fuse not the circuit or even worse you!!
Danger
Remember this circuit is VERY DANGEROUS.The mains is not isolated from the circuit in any way like it would when using a transformer.Furthermore spark gaps appear because of connections being too close to each other.This happens mainly around the mains input points where power is high.
DON'T build this if you are an amateur and do not know exactly what you are doing.
DON'T touch the circuit while connected to the mains.You will get ELECTROCUTED.
Did you notice the LED is still on even though the plug is disconnected?That's because of the capacitor still having power stored.
Take a look at the spark gaps created in my circuit because the strips are too close to each other and had solder on them.
Tesla's rule of thumb was working with one hand when dealing with high voltage.
Look at the spark gaps!!
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