Re: [oopic] Re: Single 6V battery constraint

You can make it work by powering the servos directly from the four
battery cells and powering the micro through a low-dropout 5 volt
regulator like so:

+6V--------+-----LP2954-----+--------micro
| | |
1uF C | C large cap (a few thousand uF)
| | |
battery | | |
ground-----+--------+-------+--------micro ground

The connection to the micro goes directly to the OOPic's 5V rail, NOT
to the OOPic's voltage regulator input. Make sure that the only
things being powered by this circuit are the micro and its EEPROM.

The large cap on the regulator's output keeps the OOPic running
during any brief dropouts (like heavily loaded servos starting up).

You could also try it like this and see which works better for you:

diode
+6V----->|---+-----LP2954-----+--------micro
| | |
large cap C | C 1 or 2 uF
| | |
battery | | |
ground-------+--------+-------+--------micro ground

The diode can be any general purpose diode (like a 1N4001), but if
you can get one with a lower voltage drop, it would be better.

Personally, I would go with the first circuit, since it will run on
lower battery voltage.

Links:

<http://www.national.com/mpf/LP/LP2954.html>

<http://www.mouser.com/search/refine.aspx?Ntt=5985-85-25V6800>

At 01:24 PM 11/4/2007, pvbeachdiver wrote:
>Clarification/additional information:
>
>Project will need only 2 standard servos, modified for continuous use,
>(for the drive train)
>
> e.g. HiTec HS 322 or 422,
>operating voltage 4.8 - 6.0 V,
>current drain 7.7 mA/idle and 180 mA no load operation;
>
>Batteries constrained to 4 "common, commercially available" cells
>
>==> Alkaline D cells x 4 = 6V
>
>
>Thanks!

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