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Post by Magsy on Feb 22, 2005 16:18:53 GMT
I'm using a few plugtops at the moment but the next amp I build will require more juice. I've toyed with Tangents STEPS but its not going to be that cheap. He offers up the Velleman K1823 kit as a cheap substitue. The manual for the kit is here www.velleman-kit.com/Downloads/0/Manual_K1823.pdf (200kb pdf) Maplin have the kit but it needs a transformer to go with it. This is the bit that confuses me! The transformers have two outputs, so if one is rated at 2x18v I assume this to mean 18v per secondary? The velleman kit only has two points for input, not four. Do I just use one of the secondaries? or can I pair them into one? (36v?) The manual seems to say, that fed 28vac it can produce 35v dc, how is that possible? I thought the LM317 incurred a small drop.. Help? What transformer should I buy to get a ~24-30v dc output? ( www.maplin.co.uk/Module.aspx?ModuleNo=36677&TabID=1&source=15&WorldID=&doy=22m2 )
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Alick
<100
The Fife Panther strikes again!
Posts: 41
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Post by Alick on Feb 22, 2005 20:43:24 GMT
Many transformers have dual secondary windings. You can connect them in series ( 2x18V would give 36V) or in parallel (2x18V would give 18V). The VA rating stays the same so you can draw twice the current from the parallel arrangement as from the series.
There's a typo in the transformer table in the Velleman manual. It should say 22 - 25V not 22 - 35V.
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Post by Magsy on Feb 22, 2005 22:22:10 GMT
Thanks Alick, its clear now ps. I've mailed both of your accounts, from different addresses. If you haven't got any mail then just send me your address please!
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Post by dogstar on May 6, 2005 19:00:44 GMT
it is also worth adding that many power supplies are for dual rail +/- circuits therefore the transformer can be configured thus by making a centre rail by joining together two of the secondary wires to create a 0 volt line connected to earth, then you have when rectified a +V rail and a -V rail from the other ends of the secondaries. Be sure not to connect the same secondary to itself
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