Tapping a main toroidal

akis · 7th May 2011, 10:23 PM

I have an 80VA 2x25V / 1.6A mains toroidal which I am planning to use for a simple bench PSU. The panel instruments need 5V and so I thought of winding some enameled copper wire around the toroidal aiming for 5V DC under moderate load (big LED segment displays).

I pulled out a random length of wire and wound it around, did not count the turns, and measured approx 3.8V DC after rectification + filter. I unwound the wire, measured the length, and then cut a new piece twice as long. This gave me 4.2V DC. I cannot understand this. I pulled it out and re-wound it the other direction, much more carefully and more evenly than before, and measured 4.4V DC.

How can double the length of wire (hense double the turns) not give me double the voltage?

phaselag · 8th May 2011, 02:51 AM

First measure the ac voltage, not dc, for comparison.

Second it is the number of turns, not the length. The circumference may not be constant.

paul

akis · 8th May 2011, 07:42 AM

I added another length and I have gone over 5.5AC. Happy now.

7th May 2011, 10:23 PM	#1
akis diyAudio Member Join Date: Jul 2008	Tapping a main toroidal I have an 80VA 2x25V / 1.6A mains toroidal which I am planning to use for a simple bench PSU. The panel instruments need 5V and so I thought of winding some enameled copper wire around the toroidal aiming for 5V DC under moderate load (big LED segment displays). I pulled out a random length of wire and wound it around, did not count the turns, and measured approx 3.8V DC after rectification + filter. I unwound the wire, measured the length, and then cut a new piece twice as long. This gave me 4.2V DC. I cannot understand this. I pulled it out and re-wound it the other direction, much more carefully and more evenly than before, and measured 4.4V DC. How can double the length of wire (hense double the turns) not give me double the voltage?

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
tapping differential outputs	belgiangenius	Digital Line Level	4	8th July 2010 07:25 PM
Amplimo Main TX toroidal typ 2N1357	dvb-projekt	Swap Meet	1	29th November 2009 09:06 AM
Tapping master clock	habsrock93	Digital Line Level	10	8th November 2008 01:41 AM
Best Transformers (Encapsulated Toroidal or Open Frame Toroidal)	Rixsta	Pass Labs	10	23rd April 2004 03:41 AM
drilling/tapping aluminum	elizard	Parts	32	6th March 2004 06:18 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

8th May 2011, 02:51 AM	#2
phaselag diyAudio Member Join Date: Nov 2010 Location: N.E. PA	First measure the ac voltage, not dc, for comparison. Second it is the number of turns, not the length. The circumference may not be constant. paul

8th May 2011, 07:42 AM	#3
akis diyAudio Member Join Date: Jul 2008	I added another length and I have gone over 5.5AC. Happy now.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)