Power from USB & DC Adapter (was Re: Design Files/Gerbers of SAKC V2)

Adam Wang adam at sharism.cc
Fri Jul 30 09:53:44 EDT 2010


Hi,

1, I made a mistake on D10 footprint confirmation, It must be 0805 to meet
MSCD104H. Pls change this to 0805 package.
2, maybe mark a concentric circles with central ring to mark "+" and outer
ring marked a "-" nearby DC Jack to suffer from mistakes by novices.
3, last but not least, current design of SAKC V2 have a condition that is it
can not use +5V power at the same time either from USB cable (0.5A) or DC
adapter(can be more). If using DC adapter fixed +5V in already,
you must _remember_ to take out mini-jumper on J18 first, then plug-in usb
cable to do s/w work. If you forgot that take out mini-jumper, after
plugging usb cable; There must be have power +5V "collide" together. This
UNSAFE condition will be happened once mindless to forget to take out
mini-jumper. And possibly let USB host device to be have damage or even DC
adapter source. Also if remove DC adapter, the SAKC it can only get 0.5A
from usb, unworthy a bit. so

1) remove the DC adapter reducing the hardware hacking usability of the
board a lot.
2) remove USB power, adding the need for an extra power adapter for every
user.
3) add additional circuitry to make both USB & DC power stable in all cases.
User should have the chance to update s/w from USB while still some h/w
parts connected to SAKC board's extendable 40pins header to get 3.3V supply(
actually comes from 5V) to outside application.

so I am wondering that we must solve this problem.

Also if SAKC comes with capability of having strong wide power range input,
this can make/let additional circuities connected to SAKC easiler and more
flexible with ONLY one DC adapter. Fg. real ROBOT industries works around
+12V or +9V supply. IMO if this can be true. SAKC will be more stronger.
Surely aside from cost evaluation.

How do you think?
Thanks,
Adam
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