[sdiy] PCB / Panel Manufacture

[John P Shea]

Fig 5 here

https://www.st.com/resource/en/datasheet/l79.pdf

shows how to do the protection diodes.

On Mon, 10 Feb 2020 at 1:11 pm, John P Shea <info at extrinia.com> wrote:

> Yes, in 6.1 here
>
> https://au.mouser.com/datasheet/2/389/l78-974043.pdf
>
> the fine print says the 100n “improves transient response”.
>
> 10u was for some additional filtering on the load. Some bus boards
> distribute this along the board (but do keep in rush currents in mind).
>
> Most modules would have local decoupling caps at entry.
>
> Whilst the 78/79xx has thermal and short circuit protection, your circuit
> does not have any protection should the +ve output be shorted to the -ve
> out. A 1N4002 across each output will protect against this.
>
> Also curious now, for bulk caps immediately following the full wave bridge
> rectifier, has anyone seen/used additional high frequency filtering caps on
> this side??
>
> Regards,
> JPS
>
> On Mon, 10 Feb 2020 at 12:17 pm, Shawn Rakestraw <shawnrakestraw at gmail.com>
> wrote:
>
>> John Shea, the design began with Electronotes. I decided to build one of
>> the power supplies I found in the Preferred Circuits book. When I laid out
>> the circuit, I changed the regulators to the 7812 and 7912. I left the
>> capacitors as they were in the original schematic. Having a look at my
>> datasheets just now shows 330 nF on the input of both regulators and yes it
>> is probably redundant. The positive regulator had a .1 uF "minimum" on the
>> output (I will probably leave my .22 uF on there) and the negative shows a
>> 1 uF on the output. None are electrolytic on the data sheets. I updated my
>> schematic and board so they are all the same now (like c5 and c6 on the
>> original. Not sure why Bernie drew his schematic with electrolytics on the
>> negative regulator.
>>
>> - Shawn
>>
>> On Sun, Feb 9, 2020 at 7:09 PM <rsdio at audiobanshee.com> wrote:
>>
>>> It seems that a larger via removes more copper, so it should be better
>>> to simply use more vias, each with the smallest drill supported, for the
>>> most copper connecting layers.
>>>
>>> Has anyone seen a writeup on the advantage/disadvantages comparing more,
>>> smaller vias versus fewer, larger vias?
>>>
>>> Brian
>>>
>>>
>>> On Feb 8, 2020, at 7:29 AM, Vesa Lahteenmaki <vjhl2000 at hotmail.com>
>>> wrote:
>>> > very tiny via on track to the negative regulator,  I would use much
>>> larger via because of current flowing through.
>>>
>>>
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