# Step Down Transformer from 230 to 0-6 V 1A

#### mukund_bm

Joined Aug 24, 2014
21

#### Dodgydave

Joined Jun 22, 2012
10,586
Your measuring the voltage without a load which will be approximately 6*1.414 = 8V.

#### LesJones

Joined Jan 8, 2017
3,897
There a a few reasons.
1 You are probably testing the voltage with no or very little load on the transformer so the transformer output will be a bit higher than when it is supplying the design load.
2 The capacitor tends to charge to the peak voltage of the waveform. The peak voltage of a sine wave is root 2 (1.414) times the RMS voltage. so 6 volts RMS has a peak value of 8.48 volts. The capacitor will charge to this value less two diode forward volts drops (0.6 to 0.7 volts per diode.) When the output is loaded the voltage on the capacitor drops during the time between the peaks so the average DC output voltage drops. The amount it drops on load depends on the load current, capacitor value, transformer resistive losses and transformer leakage inductance.

Les.

Joined Feb 20, 2016
4,251
Depending on how critical your load is to voltage variation, and how much the current will vary, it is probably a good idea to add a voltage regulator to your circuit. And, if that is the case, an increase of the AC out of the transformer will be needed. Generally, a regulator needs an input voltage a minimum of a few volts larger then the output voltage to operate.
And just a small point, the "-8V" should be changed to 0V. This is the point that the voltage is referred to.
Otherwise, it would normally be read as a +8V supply, and a -8V supply, giving a total of 16V.
That is not what your circuit is producing.

It may be worth your while reading up on a bit of theory.
and the power supply post starts here... https://www.learnabout-electronics.org/PSU/psu10.php

There is also this forum's education section... https://www.allaboutcircuits.com/textbook/