Re: microcontroller circuit help

Oops! I just noticed you wanted 12V out of it.. in that case, you could
try doing the same thing without the inverter! Your 12V circuit will
get power from the car battery when the charger isn't getting power,
and it'll power from the charger otherwise.

- Eric A.

On Dec 7, 3:19 pm, "lain" <slax0r.ha...@xxxxxxxxx> wrote:
What you would want to do is build your own UPS of sorts. Get a
run-of-the-mill car battery charger and a car battery,and an inverter
(12VDC -> 120VAC). Make for damn sure the charger is nothing special
and it just outputs the voltage and current needed to charge the
battery, a smart charger will damage this rig... Hook up the battery to
the inverter, and hook the charger up to the battery as well, so they
are all in parallel. Use the outlet on the inverter as your power
source. If the power goes out, the inverter will continue to draw power
from the car battery w/o interruption, and when the power comes back,
the battery will charge until its full, meanwhile the inverter is
running off the charger. It's a very very simple circuit and design,
but again, no smart/special chargers!!

One last note on this design.. don't do it indoors. If you do, be sure
to put it near a window and at least passively vent the battery out the
window, try to enclose it in a plastic container for instance, and run
a vent out the window. The reason I say this is because car batteries
produce hydrogen as a byproduct of charging, which is fine when they're
in the open air, but inside a house it's a fire hazard!

Good luck,
Eric A.

On Dec 7, 1:42 pm, mookiewoo...@xxxxxxxxxxx wrote:

Hi all
I am trying to put together a circuit that selects between a battery
and outlet depending on voltage. Something similar to this:http://www.yourgreendream.com/diy_gp_bat_charger.php
but not as complicated. Here is a block diagram to illustrate
AC
------------!-----------
| |
Battery |
-----------|-------------
Chip
Now the battery outputs 12 V while the chip gets 110V from the outlet.
It should decide, in case the battery is running out, to switch to AC.
The chip should have an internal 110 to 12V DC converter as well. Any
help in getting me started will be appreciated.

.

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