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Power Consumption of Circuit/ battery life calculation

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aksh217

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I'm using 3 Alkaline batteries()3450mAH to power my circuit, In my circuit Microcontroller consumes 300uA Current in active mode and 0.1uA current in power down mode and RF IC consume 11.5mA current in supply mode and 1uA current in shutdown mode so I want to know how much power my circuit consumes and how many days my battery takes to discharge.
 

Are you surprised when I tell that you need to know the duty cycle of each device, percentage of µC and RF IC active operation?
 
Hi,

or in other words:
how many % in one hour does the ciruit draw xx current? then multiply the current with the % and get the average mA for thiis situation.
one line per each situation until you get the sum of 100%.
then add all average currents.


Example:
95% it is idle with 0.1mA --> 95% x 0.1mA = 0.095mA
4% it is active with 10mA --> 4% x 10mA = 0.4mA
1% power burts with 50mA --> 1 % x 50mA = 0.5mA

now add up: 0.095mA + 0.4mA + 0.5mA = 0.995mA

If your battery can suply 3450mAh then: time = mAh / mA = 3450mAh / 0.995mA = 3467h

Klaus
 
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    d123

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Also....
does the microcontroller drive anything else?

LEDs? Switches with pullups? Displays? Buzzers?
 

Hi,

or in other words:
how many % in one hour does the ciruit draw xx current? then multiply the current by the % and get the average mA for this situation.
one line per each situation until you get the sum of 100%.
then add all average currents.


Example:
95% it is idle with 0.1mA --> 95% x 0.1mA = 0.095mA
4% it is active with 10mA --> 4% x 10mA = 0.4mA
1% power burts with 50mA --> 1 % x 50mA = 0.5mA

now add up: 0.095mA + 0.4mA + 0.5mA = 0.995mA

If your battery can suply 3450mAh then: time = mAh / mA = 3450mAh / 0.995mA = 3467h

Klaus

My circuit also drives 2 switches, 3 LED's and 1 0.5 W speaker so can I also add this devices power consumption into this.
 

Hi,

how many % in one hour does the circuit draw xx current?
I clearly speak about circuit current, this means all current that drains out the battery..

Klaus
 

Also....
does the microcontroller drive anything else?

LEDs? Switches with pullups? Displays? Buzzers?
Switch takes 10mA of Current and it takes 5ms to contact bounce so how much current it consumes in 1 press.
also led takes 30mA forward current with power dissipiation 100mW so how much current it takes for glowing 1 to 3 Sec.

How could I know duty cycle for all of these?
 

Hi,

How could I know duty cycle for all of these?
If you don´t know ... nobody knows.


Klaus
 

Did you consider that the battery voltage starts at 4.5V but continues to drop? Will your circuit work when the battery is 3V? 2V?
 

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