[sdiy] PSU problem

[Carlos Portela]

Thanks all.


2014-05-28 22:01 GMT+02:00 Donald Tillman <don at till.com>:
>
> On May 28, 2014, at 12:40 PM, Carlos Portela <carlosrochaportela at gmail.com> wrote:
>
>> Don - The transformer only has 2 cables, not ground. the ground its
>> the dashed line.
>
> And that's exactly the problem; you are missing a ground.
>
> For a transformer without a center tap secondary, you should ground one of the secondary wires and run the other wire into two half-wave rectifiers for your positive and negative regulators.
>
> Dashed line for ground?  Ground should be the most important concern.  Note that in the drawing the transformer never makes it to ground.)
>
>
>> Julien - the transformer its 16VAC but I measured 18.6VAC. Also tried
>> with 18VAC tranformer (measured around 21V)and got the same problem.
>
>
> 18.6 Vac is a reasonable no-load voltage for a 16 Vac transformer.
>
> 16 Vac will peak at 22.4 V, with a little droop and rectifier drop, that will come down to about 20 Vdc which is completely fine for the 15 V regular chips.
>
>   -- Don
>
> --
> Don Tillman
> Palo Alto, California
> don at till.com
> http://www.till.com
> 650 888-9632
>
>
>