Multitap transformer question

In the things that I build I often need a mains transformer with multiple secondary windings, the first a center tapped 30V winding to give me +/- 15 Volt rails, and a second 9V winding to give me a +5 Volt supply. These Xformers come from Farnell and are expensive, so I was wondering if it would be possible to use a cheaper transformer that has only one secondary winding but lots of taps? there is a relatively cheap one at Jaycar with 0, 9V, 12V, 15V 18V, 21V, 24V and 30V taps.

Can I for instance use the 0 - 15 - 30 taps for my +/- 15 supply and at the same time use the 9V tap for the 5V supply, or will this cause symmetry and loading problems within the transformer?

I would think that those "cheapies" are an either/or choice, I can't imagine that they would stand up to multiple tap use !!
If the overall ratings were high, like 30Va then they get more expensive ..right ?
MM.

Why not get a 30v CT Transformer to get your +/-15v and then regulate the +15 volt to +5v , as long as there is enough current available for all parts of the curcuit then there shouldn"t be any Loading problems....

[quote author="Steve Jones"]Can I for instance use the 0 - 15 - 30 taps for my +/- 15 supply and at the same time use the 9V tap for the 5V supply, or will this cause symmetry and loading problems within the transformer?[/quote]
The 15 will be ground, so the 24 could be your 9v.

[quote author="walter"][quote author="Steve Jones"]Can I for instance use the 0 - 15 - 30 taps for my +/- 15 supply and at the same time use the 9V tap for the 5V supply, or will this cause symmetry and loading problems within the transformer?[/quote]
The 15 will be ground, so the 24 could be your 9v.[/quote]
The 15 to 21V tap with halfwave rectifier giving 8.5V - 1 diode drop might also fit if heat is an issue.

[quote author="walter"][quote author="Steve Jones"]Can I for instance use the 0 - 15 - 30 taps for my +/- 15 supply and at the same time use the 9V tap for the 5V supply, or will this cause symmetry and loading problems within the transformer?[/quote]
The 15 will be ground, so the 24 could be your 9v.[/quote]


Oops, well spotted!

[quote author="Harpo"][quote author="walter"][quote author="Steve Jones"]Can I for instance use the 0 - 15 - 30 taps for my +/- 15 supply and at the same time use the 9V tap for the 5V supply, or will this cause symmetry and loading problems within the transformer?[/quote]
The 15 will be ground, so the 24 could be your 9v.[/quote]
The 15 to 21V tap with halfwave rectifier giving 8.5V - 1 diode drop might also fit if heat is an issue.[/quote]

Good point, keep the voltage drop down across the 5V regulator to keep the heat down.

That transformer should work just fine. How much current are you going to be pulling off the 5V supply?

[quote author="BYacey"]That transformer should work just fine. How much current are you going to be pulling off the 5V supply?[/quote]

Not sure yet, I am still designing things at the moment. Bet it's cold in Canada now, I just spent a lot of time there working over the last 2 years, hope you are keeping warm...

[quote author="Steve Jones"][quote author="BYacey"]That transformer should work just fine. How much current are you going to be pulling off the 5V supply?[/quote]

Not sure yet, I am still designing things at the moment. Bet it's cold in Canada now, I just spent a lot of time there working over the last 2 years, hope you are keeping warm...[/quote]

Naw, it's nice here today, it warmed up to about -6C.