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[on:]

Hi all, in order to improve the durability of the batteries I was studying the possibility to replace the 7805 with a boost converter or with a step up-step down converter. The project I'm working on uses a microprocessor 1284, lcd dispaly, a rtc, a adc 12-bit, a pressure sensor and three oxygen sensors. And I would feed the device with a maximum of 2 batteries of 3.6 V. The device is in sleep as long as you do not press a button that wakes up via interrupt the microprocessor and the display lights up. In sleep mode, the all-consuming as few mA when lit consumes about 90mA.

Boost converter
http://www.pololu.com/catalog/product/798

StepUp-stepdown coverter
http://www.pololu.com/catalog/product/2119

and the battey
http://www.atbatt.com/product/3443.asp

Obviously using the boost converter would use only a battery.
What do you recommend? I wish it had at least 50 hours of operation and sleep mode in a few months.

Best Regards

Marco

[Reply #1 on:]

I think I'd go with the first regulator. Nice low current drain for the part itself.
If you  can switch off power to the other devices before into power down sleep mode that should cut down on current draw.

[Reply #2 on:]

I too would recommend the boost regulator and the use of a single Li-po cell. Using a single cell makes the li-po charger requirement simpler as there is no worry about a two cell battery going 'out of balance' or requiring a special 'balancing' charger set-up. Just size the single cell mAH rating for the run time duration the project requires. In this day and age with inexpensive switching regulators no one should be using old fashion linear voltage regulators with battery powered projects.

Lefty