Limiting current consumption of the device

[paddy_p]

Hi,

Greetings of the day!!!

I have to design portable battery operated device. Battery is from Tadiran make TLL 5902. The device containing micro controller,sensor, LED's, Buzzer and vibrator and LCD display.
The battery should work for 20,000 hours is the major requirement. To achieve this battery life my circuit consumption should be approximately 100uA. With all such components how do I achieve the battery life of 20,000 hours.
I have attached battery datasheet for reference.
Also suggest LCD for this application.
Please advice!!

View attachment TLL-5902.pdf

 

[Audioguru]

The battery datasheet shows a load current of 100uA makes its life only 10,000 hours. You must reduce the load current to only 50uA for a battery life of 20,000 hours. If you cannot reduce the current then the battery is too small.

 

[paddy_p]

It will be great if anyone suggest how do I reduce load current.
Suggest some ultra low power consuming components like LCD,LED's, Buzzer, Vibrator if available.

 

[BradtheRad]

Flash led's briefly at a slow rate. Same for the buzzer and vibrator.

 

[Audioguru]

I designed and built some LED chasers that have 10 LEDs in a circle and a blink of light goes around and around. Chasers with 1.8V red LEDs are powered from two AA alkaline battery cells and chasers with 3.2V blue and bright green LEDs use four AA alkaline cells. The batteries run the chasers all the time day and night and last for 3 months even though the LEDs are bright at 27mA when the batteries are new.

How?
1) I used Cmos logic that draws no current when stopped and when running slowly.
2) The sequencer IC is a 74HC4017 that always has one LED lighted but I added a circuit that blinks each LED for only 30ms.
3) Instead of the chase going around and around continuously I added a circuit to allow it to chase around for 3 times then a pause for two seconds before chasing again.
4) The circuit draws no current from the battery during the pauses.

The chasers work fine until the total battery voltage drops to less than 1.5V for the chasers with red LEDs and less than 3V for the others.

3 months is 2160 hours. The AA alkaline cells have a capacity of 3000mAh. The LEDs have a current of 27mA when the battery is new but a current of maybe 5mA after 3 months so their average current is 16mA.
If the circuit allowed one LED to always be lighted then the battery must have a capacity of 16mA x 2160 hours= 34,560mAh.

So I reduced the average current and the size of the battery to 1/12th. If I slow down the chase then the average current will be less and the batteries will last longer.