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

David Reyes Samblas Martinez david at tuxbrain.com
Fri Jul 30 11:17:51 EDT 2010


I must agree with Ron that we don't have to save in "poka yokes" on
the power sourcing on SACK
+1 to the  +/- protection
+1 to the +5V collide protection

and how much cost and space is for the power regulator?

2010/7/30 Ron K. Jeffries <rjeffries at gmail.com>:
> Please make sure that the design protects
> against plus and minus being plugged in wrong.
> I think that implies a zener diode.
> the extra cost of a 5V supply that accepts a fairly
> wide range of input voltage say 12v or less
> is probably worth it IMO
> SAKC is prolly less price sensitive than Nanonote.
> ---
> Ron K. Jeffries
> http://ronkjeffries.posterous.com
>
>
>
>
>
>
>
>
> On Fri, Jul 30, 2010 at 07:44, Carlos Camargo <cicamargoba at gmail.com> wrote:
>>
>> Hi Adam
>>
>>
>>
>> On Fri, Jul 30, 2010 at 8:53 AM, Adam Wang <adam at sharism.cc> wrote:
>>>
>>> Hi,
>>>
>>> 1, I made a mistake on D10 footprint confirmation, It must be 0805 to
>>> meet MSCD104H. Pls change this to 0805 package.
>>
>> ok, I'll fix it
>>
>>
>>>
>>> 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.
>>
>> Agree
>>
>>>
>>> 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.
>>
>> Yes, I'm trying to solve this issue, I think that we can use a single
>> circuit Power On Reset + Transistor:
>>                             TRANSISTOR
>> USB_VCC-------------|S|           |D|----------- 5V
>>                                                        |
>>                                      |G|              |
>>                                        |               |
>> DC_WALL------|  POR |----------------------
>>
>>
>> When DC_WALL = 0V  Transistor is ON so 5V = USB_VCC
>> when DC_WALL >= POR's threshold => Transistor is OFF =>  5V = DC_WALL
>>
>>>
>>> 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.
>>
>> We can't provide all the possible voltages for all the possible
>> applications. We can add an additional 5v regulator with a wide input range,
>> but this increase the cost & the size.
>> Carlos
>>
>>
>> --
>> Carlos Iván Camargo Bareño
>> Profesor Asistente
>> Departamento de Ingeniería Eléctrica y Electrónica
>> Universidad Nacional de Colombia
>> cicamargoba at unal.edu.co
>>
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-- 
David Reyes Samblas Martinez
http://www.tuxbrain.com
Open ultraportable & embedded solutions
Ben NanoNote, Arduino, Openmoko
Hey, watch out!!! There's a linux in your pocket!!!




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