On 27-08-2012 23:50, Anand P. Paralkar wrote: > Hi, >
Hi Everybody,
Firstly, thanks a lot for your detailed replies. Although this started-off as a thread on my doubts on the transformer, this thread got (unintentionally) drawn to another topic. One that I was planning to post here anyway.
The reason I said that getting both - the positive and negative source from a transformer without a center tap is difficult is that I tried what a lot of people have recommended here. I built a circuit that had the two diodes connected to the transformer secondary. One diode had its anode while the other had its cathode connected to the transformer secondary. The other end of these diodes were connected to a capacitor each. These capacitors had a common point which we could call the ground.
I was surprised to find that this ground actually drifted! When I measured the voltage across the ends of the capacitors (the end connected to the diodes), the voltage measured was constant. However, when I measured the voltage across the ground and the other end of the capacitors, I saw that this voltage changed. So the V+ source and V- source with respect to the ground was not constant!
I don't know the exact reason what causes this drift. But as a remedy, I put a resistor in parallel to each of the capacitors. (P. E. Schoen has posted this).
This stopped the ground from drifting but I don't think one could use this solution in a practical circuit. A resistor in parallel at the output of a voltage source will not hold up in case of a heavy load (low load resistance).
That's why it seemed difficult.
There are ofcourse many other circuits that have been suggested here. Thanks a ton gentlemen.
Thanks, Anand