Wednesday 4 January 2012

Step-down AC without using a transformer.


High everyone!!!!
In this article, I will show how to step-down AC for higher current output without using a transformer.

This circuit is meant to work for only AC operating motors!
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This is a common question, being asked by many newbie (even by me also) but answers are hard to find. One day I sort out the possibility when I looked a scrap circuit. That circuit is very common to all of us.
In this method, I will use a triac to minimize the voltage. This circuit can be used for a power consumption of about 100W or more, depending on the size of heat sink you are using.

TRIAC or Triode for Alternating Current is an electronic component that can conduct current in both directions when it is triggered (turned on). These are considered as an AC switch. The gate current to trigger the triac can be as low as 10mA to 50mA and increase in gate current will increase the voltage output. The output voltage can be as low as 5V AC and as high as 220V AC.

Below is the schematic of a voltage controller:


Here DB3 is a DIAC which can only supply a voltage greater than 30V. It is used to make an operational limit for the output of the triac. If mains voltage falls from 220V and the gate voltage is lower than 30V, the circuit will break. However, you can remove the diac if you are working in a low mains voltage or want to drop the triac’s output very low. R5 is a current limiting resistor and is optional.
To increase the output, you have to decrease the value of R2 or R4, and vice versa.

Component details:
3.       Triac = BT136 or equivalent
4.       Diac = DB3
5.       R1 = 68Ω 1/4W
6.       R2 = 5.6KΩ 1/4W
7.       R3 = 750KΩ 1/4W
8.       R4 = 600kΩ potentiometer
9.       L1 = 100uH

Note: This schematic is designed by me and I will not guarantee for any malfunctioning and damages of components. This is a high voltage application and proper precautions should be taken.