transformer wiring

happysacbrewing · Joined: 20 Jan 2011 Posts: 34 Location: Edgewater, MD

I got my 120V - 12V transformers in the mail today and am walking through how to hook them up. I have two blue wires coming out on the primary side and two smaller black wires coming out on the secondary side. There is no documentation with them or that I can find online and the place I bought them is not helpful. I was wondering if someone here could verify whether my understanding of how these work is correct and help with a few questions.

I think on the primary side it does not matter which wire goes to hot and which goes to neutral, as long as AC is flowing through the coil it should work. On the secondary side, I understand that both of the secondary wires are going to be connected to the variable DC power supplies (which I haven't gotten yet), is one positive and one negative? I would think they would have to be, but I don't know how to tell which one. There is a dot on one side of the transformer, does that usually indicate the positive output?

Thanks for the help.

rosenjm · Joined: 21 Dec 2010 Posts: 249 Location: Ballston Spa, NY

Don't confuse a transformer with a rectifier. Both the in and the out of your transformer will be AC and therefore polarity is not important. All it is doing is stepping down the voltage from 120V to 12V. Once the power leaves your DC power supply (rectifier), you now have a positive and a negative and polarity makes a difference. Hope that helps.

happysacbrewing · Joined: 20 Jan 2011 Posts: 34 Location: Edgewater, MD

That is exactly what I was confusing. It is all clear now. Thanks.

crush · Joined: 28 Dec 2010 Posts: 706 Location: Telemark, Norway

Just to add to what rosenjm wrote, the rectifiers are the AC/DC coverters that Kal has used in the control panel. (I got mine here http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=300508921400&ssPageName=STRK:MEWNX:IT[)

In our application, they take AC as input and produce DC, so the connection order between the transformer and these rectifiers does not matter. On the transformers, you only need to worry about which is in and which is the out side. The polarity on either side is not important.

Polarity is only important on the output side of the rectifier, because it is DC.

EDIT: Ah, I wrote this before I saw your reply. Glad that it's all clear for you now!

happysacbrewing · Joined: 20 Jan 2011 Posts: 34 Location: Edgewater, MD

Thanks Crush. That is very helpful. I am trying to make sure I understand how everything flows before I start touching any wires. I could never do this on my own, but between the detailed directions and the helpful folks in the forum, I think I might actually be able to figure it out. Cut all the 22 mm holes in the panel yesterday. Still a bunch more cutting to do, so I have some time to work through all the wiring stuff. Thanks again.