Transformer less power supply

C1 = 0.22uF,400V
R1 = 1M ohm, 1/4 watt
Diodes = 1N4007(D1,D2,D3,D4)
C2 =220 uF,25V
R2=330 ohm,1/4 watt
R3=680 ohm,1watt

Generating Low voltage DC, from the 220v or 110v AC mains, is very useful and necessary in the field of electronics. Low voltage DC, like 5v, 6v, 9v, 12v, is used in electronics circuits, LED bulbs, toys and many household electronics items. Generally batteries are used to power them, but they need to be replaced time to time, which is not cost effective and also takes our time & energy. So the alternative is to generate the DC from AC mains, for which there are many AC-DC adapters are available, but what circuitry they are using inside?

The easy and straight forward approach is to use step-down transformer to low down the AC, but the disadvantages of using transformer are that they expensive in cost, heavy in weight and big in size. We have already covered this type of AC to DC conversion, using Transformer in this article Cell Phone Charger Circuit. And yes, we can also convert the High voltage AC into Low voltage DC, without using the Transformer, this is called Transformerless power supply. The main component of a Transformerless power supply circuit is Voltage dropping capacitor or X-rated capacitor, which are specially designed for AC mains. This X rated capacitor is connected in series of Phase line of AC, to drop the voltage. This type of Transformer less power supply is called Capacitor Power Supply.

X-Rated Capacitor

As mentioned they are connected in series with phase line of AC to lower down the voltage, they are available in 230v, 400v, 600v AC or higher ratings.

Selection of voltage dropping capacitor is important, it is based on Reactance of Capacitor and  the amount of current to be withdrawn. The Reactance of the capacitor is given by below formula:

X = 1 / 2¶fC

X = Reactance of Capacitor

f = frequency of AC

C = Capacitance of X rated capacitor

We have used 474k means 0.47uF capacitor and frequency of AV mains is 50 Hz so the Reactance X is:

X = 1 / 2*3.14*50*0.47*10-6 = 6776 ohm (approx)

Now we can calculate the current (I) in the circuit:

I = V/X = 230/6775 = 34mA

So that’s how the Reactance and Current is calculated.

List of Parts: 
light-emitting diodes (http://amzn.to/2oKv9eS)
Resisters
Capacitors
soldering iron(http://amzn.to/2oxTJNS)
multimeter(http://amzn.to/2oBLSRb)
screwdriver(http://amzn.to/2p4XDkn)
solder(http://amzn.to/2oy1kMn)
hot glue.(http://amzn.to/2oy4GPL,http://amzn.to...)
Try and assemble by yourself this very promising and cost-effective light source.

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