Are they mains transformers with two equal voltage center tap secondaries ( 6 terminals at the secondaries ) ?
Or a variant four equal voltage secondaries ( 8 terminals at the secondaries ).
This is just to know wether this is popular or asks for a custom winding.
Or a variant four equal voltage secondaries ( 8 terminals at the secondaries ).
This is just to know wether this is popular or asks for a custom winding.
It's a bit hard to understand your question for me, but if understand you right: you ask about whether to order a transformer with center tap or isolated windings? The answer is usually - It is almost the same for manufacturer, so you may order a variant you need.
With center tap it is only a one wire cheaper for a manufacturer.
(As for me - I prefer isolated windings).
With center tap it is only a one wire cheaper for a manufacturer.
(As for me - I prefer isolated windings).
If I understand you want to know if 4 winding transformers are common - either 4 individual windings or 2 center tapped windings.
I would say no. Most are 2 windings, or 1 center tapped. If you pull up something like Farnell all their parts are 2 windings. If you want 4 custom would be the way to go.
Also idividual windings are more flexible than a center tapped type.
I would say no. Most are 2 windings, or 1 center tapped. If you pull up something like Farnell all their parts are 2 windings. If you want 4 custom would be the way to go.
Also idividual windings are more flexible than a center tapped type.
This means: To make a dual rail PSU,
+V Ground -V, using two identical regulated PSU, with a common transformer....The only way is a two windings transformer with two diode bridges.
The extra cost of a custom transformer is likely more than the saving on 4 diodes instead of 8.
+V Ground -V, using two identical regulated PSU, with a common transformer....The only way is a two windings transformer with two diode bridges.
The extra cost of a custom transformer is likely more than the saving on 4 diodes instead of 8.
You can use two winding transformers with 1 bridge rectifier, just join the two windings together to give you the center tap (observing phasing), use the connection between windings as 0V/ground, then the other ends go to the AC connections on the bridge rectifier, then just one set of capacitors.
However two bridge rectifiers should be better, you can get a lot of current flowing in the "center tap" (where you join the two windings, allegedly, i've never measured it). Then join the + and - of the two bridges to give 0V.
Drawing schematics might be clearer, too many
though...
However two bridge rectifiers should be better, you can get a lot of current flowing in the "center tap" (where you join the two windings, allegedly, i've never measured it). Then join the + and - of the two bridges to give 0V.
Drawing schematics might be clearer, too many
though...
You missed the requirement: Using two identical regulators.
In other words, I do not want to use a positive regulator and a negative regulator. I want to use two regulators of the same polarity.
Then you cannot join the + and - of the two bridges to give 0V.
In other words, I do not want to use a positive regulator and a negative regulator. I want to use two regulators of the same polarity.
Then you cannot join the + and - of the two bridges to give 0V.
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