Hi! Recently I purchased a 12V, 300mA transformer which has three terminals (Black, yellow, Black) for its output. I have used transformers which has 2 terminals. I like to know what these terminals represents and which terminals to use when using it to obtain 12V DC.
If there is a low resistance between the black terminals and the yellow one, it is a centre tapped transformer, you will have to put mains on its primary to see if its a 6-0-6 =12V with a bridge rectifier across the black terminals. Or its a 12-0-12, which will give you 12 V with two diodes on black terminals with the output on the common diode connection and the yellow terminal.
Frank
If you insist on using a bridge rectifier, connect the black terminals to the AC input terminals of the bridge, use the + terminal as your + output use the yellow terminal as the - output. You are only using 1/2 of the bridge.
Frank
That's a different solution. The two-diode fullwave rectifier suggested by chuckey will be slightly better in two regards
- symmetrical loading of transformer windings
- less rectifier voltage drop and power dissipation
I tried it with use of a 2200uF and its working. But I can hear a very low noise from the transformer (Kind of a humming). Is it some kind of fault or is it usual to hear it?