V G <x.solarwind.x <at> gmail.com> writes:

>=20
> Hey all,
>=20
> Here's my very simple guitar tuner board.
>=20
> Schematic: http://postimage.org/image/yqrtiyh0/
> Unrouted PCB: http://postimage.org/image/yqth2ays/
> Routed PCB: http://postimage.org/image/yqq5zlz8/
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> I'm planning to get it made with DorkbotPDX. $5/sq in and you get 3 copie=
s
> of the board.
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> The board is powered from 3V (2 x 1.5V alkalines), has 2 push buttons for
> picking string/other function, has a slide switch for power, crystal with
> capacitors, ICSP header, 6 surface mount LEDs for staus/string choice, tw=
o
> high brightness LEDs for oscillating.
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> Just realized - those high brightness LEDs take 30mA, but the PIC can't
> provide 30mA on each pin. I'll probably stick a couple of small BJTs on
> there. Maybe two MMBT2222 type.


1. Transistors to drive LED: it's easier to tie LED to Vcc and use BJT as l=
ow
side switch;
2. Capacitors: recommend a larger caps (in addition to decoupling 0.1uF tha=
t you
already have) to handle high LED current and prevent large volt drop on the
battery.  It might be a non-issue with fresh cells, but as they are used up=
, the
internal resistance will increase. =20

Sergey Dryga
http://beaglerobotics.com


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