[sdiy] Newbie Voltage requirements question

[m.bareille at free.fr]

Hi,

Very simple :

1) Vintage DS7 :
  It contain a 7805/ to92 case, and no external PSU plug . This module accept no
more than a 9V battery. If more voltage is applied ( say 12V...) the DS7/8
become noisy ( background noise) , because the 7805 is overvolted and start to
do 'strange' things , but it still work... I did not try with more than
12VDC...


2) Vintage DS8 : Contain a 7805/ TO220 case and an external PsU plug . So This
module can accept up to 35V DC . The DC limit of the 7805/to220 input is 35V if
i remind well...)


3) Clones DS7/DS8 : Both are supposed to be assembled with 7805 TO220  even if
some of my protos are fitted with TO92 rgulator ... You can put a To92 one ,
but this will hardly limit the PSU voltage to a clean 9VDC max...


Now , if you forget the voltage regulator , it is clear that the internal
circuits of the DS7/8 are working under 5V , like most of the Logic ics ;) So if
you have a clean 5V source , you can forget the 7805 ( any cases ...)and connect
the +5V directly at the output pin of the 7805 on the DS7/8 pcb.

So my advice are:
1) remove the +5V reg and use a clean +5V DC source
or
2) use a 7805-TO220 1A ...


Cheers,

Marc B.


Selon Sam Ecoff <secoff at execpc.com>:

> Hullo again...
>
> Back with another newbie question, this time about voltage
> requirements. I'm considering building some of Marc Bareille's DS8
> clones (http://m.bareille.free.fr/ds7clone/ds7.htm) but I am somewhat
> put off by the fact that they require 5V. My modular has Modcan and
> Frac in it right now, so I'd love to be able to run them off of the
> 15v blacet supplies I have. So... I looked at the DS8 schematic, and
> it was immediately clear that 15v is out of the question as the 7805
> 5v voltage regulators can handle 7.5v max according to the spec sheet
> I read. So, this gets me thinking, why couldn't I replace the 7805's
> with 7815's? Obviously, the 16v caps would become 25v, but from what
> I saw in the spec sheets, the other components can all handle 15v.
> So, is it as easy as swapping out the Voltage regulators, or is there
> a lot more to it? I understand the principle of Ohm's law, V= I x R,
> but I am so new to electronics that I don't yet understand the
> ramifications on a circuit.
>
> At the end of the day, would it just be a heck of a lot easier to
> build the circuit as designed and buy a Rat shack 5V wall wart to
> power it? Also... there's some note about using 9v to power the
> circuit here http://m.bareille.free.fr/ds7clone/ds7wiring.gif at the
> bottom left, but it's in French and www.freetranslation.com was of no
> help. In fact, the pic of his prototype shows a 9 volt battery
> connector. This confuses me b/c the data sheet I saw for a 7805 said
> that 7.5v was the max.
>
> Thanks for the help or advice.
>
> Sam E.
> _______________________________
> Sam Ecoff
> Secret Society Productions
> 5307 S. 92nd St. Suite 105
> Hales Corners, WI 53130
> (414) 427-0615
> www.samecoff.com
>
>
>