I am thinking of using 2 x CR2032 (for space considerations and increased mAh) which would give me 6v to run a 328p chip.
I was wondering if this would be the right approach?
NO.Voltage dividers are ok for signals or analog input but not for power input voltage reduction.You would be better to use 3 batteries and use the external dc barreljack as the input.Also, I would not choose a 2032 coin cell to run a microprocessor , even if it is only an ATMega328.Find some other battery, like litheum-ion. Two 18650 batteries in series is 2*3.7=7.4V which is ideal input voltage for a 5V regulator.So get a 5V regulator, two 18650 batteries , a dual series battery holder, one or two TP4056 lithium-ion battery chargers and then your set.
It is going to be hard to get enough current through 1 megohm and 100 kohm resistors unless you are planning to put very many in parallel. Of course I don't know what you are planning because you did not explain. Remember that your Arduino acts similar to an additional resistor except that it is variable.The voltage divider approach is not practical using batteries as an input.A series diode (e.g. 1N4001) may be a more practical approach.
+1 for a single CR2032 if you really want to go low power. Use the internal 8 MHz clock; sleep most of the time; and indeed your project will be able to run for a really long time. Use an RTC with alarm for the countdown part; super low power use, accurate countdown and the MCU can sleep until it's time to sound the buzzer. Well, it doesn't even have to wake up for that, the alarm output of the RTC can activate the buzzer.2x LiPo makes you lose LOTS of power. About 32% over the regulator - not counting its quiescent current (which can be much higher than what the ATmega328p uses while asleep).
Hi,I am thinking of using 2 x CR2032 (for space considerations and increased mAh) which would give me 6v to run a 328p chip. I was thinking of using a voltage divider (1MΩ and 100KΩ resistors) that would drop it to 5.45v. The project would be for a simple countdown timer that would then trigger two 5V active piezo buzzers.
Thanks for any guidance in advance.
For rough timing use WDT. For precise timing may be used Timer2 clocked by a watch crystal.I have no idea how loud the buzzers need to be but driving a passive piezzo directly from ATMega pins may do decent sound even at 3V.This is also interesting low power "tutorial".