dual voltage transformer?

Parts Questions
1

http://uk.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=1214645

would this work for a psu for my SID? it outputs 7VAC and 17VAC. i’d regulate them to 5VDC and 15VDC. i’m just a bit unsure whether or not it would work being that it is a flyback transformer allegedly…

cheers

2

Looks pretty good. But there are a few things to consider:

  • Use low-drop voltage regulators - this way you´ll certainly be on the right side (dropping 7 V to 5 V with a standard 78xx *might* be a little on the edge).

  • SHIIIIIELDING - these standard trafos certainly bring in a BUNCH of hum. Either put it into a external box (best way perhaps) and shield it (e.g. just use a metal box) or shield it thoroughly within your box (metal plates everywhere - pulled to ground).

  • Working with high voltage (125 V AC) is NOT FUNNY AT ALL. It´s kinda dangerous (I talk about something I do know … two times … *cough*) and dammit it hurts! So only work on that if you KNOW what you´re doing and be extra-super-doopa-ultra-color careful.

3

thanks for the reply!

i went with a different one in the end. it outputs 4x7VAC. i’ll connect two in series for 14VAC and two in parallel for 7VAC at twice the current capacity of one secondary.

7*1.42=9.94VDC how much will the rectifier and 7805 take away? i have almost 5V to play with, right?

cheers

4

If sheilding is an issue (which it will be, if it’s in the same box), try finding a toroidal transformer instead.

5

it is a toroidal one, why is that better? do they give out less hum?

6

Yep, and they have better efficeny, too. Overall .. they’re just better…  ;D

With a heatsink attached, the 7805 will take the 10 V easily.

7

nah i meant ‘would it be enough’? you said dropping 7V to 5V would be a close call for a 7805.

8

aaaahhh, ok.

-> yup…  ;D