https://crcomp.net/arpanet/index.phpRich S wrote:
Don wrote:
Many consumer grade USB power banks come with a built-in
automatic shutdown circuit. Light loads, such as the nominal
6.8 μA drawn by a portable MP3 player, are not enough to
prevent shutdown. To compensate, this project uses
a 555 to nominally pull 100 mA every 5.5 seconds.
( excerpt - read more at https://crcomp.net/mp3mod/index.php )
Hello Don, you\'re obviously a handy guy, so
why not just open up the power bank, and
bypass that \'auto-shut-off\' circuitry?
Maybe you use this power back for other uses?
So you still want the auto-shut off?
I don\'t see the logic why that feature is needed
in the power bank, anyway. Any electronic device (beyond
a simple thing like a light) is likely to have its own auto-shut
-off function.
But you do want to preserve it, then I\'d install a simple
SPST switch to select bypassed- or native-behavior
as you like.
One reason for me to leave the Power Bank unopened is it may open a can
of worms. Especially if it uses an undocumented, expoxied, exposed-lead
chip to control its charge cycle /and/ perform an automatic shutdown.
Also, my tear-down of the MP3 player to remove its battery and USB-B
port already sated my appetite to take things apart (for now).
You didn\'t comment on my MP3 player. Muchas Gracias. After all, the
player\'s merely an available adjunct to test my keepalive with a field
trial.
Although the keepalive functioned as originally intended, the prospect
to double its efficiency tempted me to replace R2\'s original 150 K ohm
value with a 300 K ohm. So my page now reflects R2\'s new value:
https://crcomp.net/mp3mod/index.php
The keepalive successfully functions on two distinct Power Banks
with different capacities, marketed under separate brands. Besides auto-
shutdown, both Power Banks also share similar design language [1], as if
they both originate from the same factory in China.
Note.
[1] https://encyclopedia.thefreedictionary.com/design+language
Danke,
--
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.