> So, will 10v-ratings work or will it be a too narrow margin?

No, it is way below what you need.

- 9V AC gives (at most, which is what you want to calculate with) 9 x
sqrt(2) = ~ 12.7 V
- an unloaded small 9V transformer can give much more than 9V (measure
or find the specs), calculate with at least 12V, maybe even 18V
- mains has a wide margin. I don't know your countries specs, but I
would calculate with at least -20 +20 %, maybe (much) more
- elco's don't like too high volatge. If my max-max calculations would
yield 15V I would never choose a 16V, maybe not even a 22V.

> The PSU will be connected to a 7805, so I'm not expecting too 
> much variations (except for perhaps inferior) in the voltage.

I don't get that. An 7805 will limit the output variations, but it can't
infuence its input voltage (except by doing weird things when it is not
decoupled, or too high, or too low).

Wouter van Ooijen

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Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: www.voti.nl/hvu
 
 

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