Harish Mekali

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11 years, 1 month ago.

what specification battery i need to use for mbed board it has LCD display,few resistor sensors?

specification of rechargeable battery by solar energy?

3 Answers

X M
11 years, 1 month ago.

You can power the mbed board with the least possible operating Voltage (4.5 V ) , since the excess voltage comes to heat at the on board power regulator chip .... So you just have to measure current drawn using a multimeter ( during full and sleep activity ) [[ http://mbed.org/blog/entry/New-Cortex-M0-mbed-having-a-snooze/

Regards , Christos

Accepted Answer
Ney Palma
11 years, 1 month ago.

Well Harish, i think that depends in two things:

  • Voltage needed
  • Current drawn by the componentes used

You need five volts to make the mbed and LCD(this only work at 5 volts generally) works. And for the current:

  • The mbed LPC1768 drawn according to the specs approximately 200mA
  • An LCD with backlight drawn approximately 240 mA

So with this information you need a battery that have:

  • 5 volts
  • At least 440 mAh

The battery capacity is measure in mAh (milliamps Hour). To know how much time your device will be operating, you use the formula

  • Hours of operation=(Battery Capacity/Current drawn by the device)

So if i have a 440 mAh battery and my device consume 440mA my device will be operating one Hour

  • 440mAh/440mA = 1 hour

I hope this info help you

Greetings

Harish Mekali
poster
11 years, 1 month ago.

Thank you Mr. Ney Palma, :)

I am planing to use a battery with 7.5v and 1.3Ah. I think this should work normally for 2.8hrs in continuous on state.

Our application is such that for every 30 mins controller will come out of sleep mode and logs the sensor data into *.csv file and goes back to sleep mode again. Then, Hours of operation = 1.3Ah / Current drawn by device in sleep mode + on mode

In such a case how to measure the current in sleep mode and on mode for total circuit? (apart from the specs, I wish to measure the current consumed directly from the circuit)

Hi Harish, is you plan to use 7.5 v battery just remember to use a 5v regulator for the LCD display (the maximum operation voltage of the LCD is 5.5 v so be careful). The operating voltage range of the mbed is 4.5 v to 9 v so there is no problem with the 7.5 v

And like X M said, you can measure the current drawn by your circuit with a multimeter. Here is a sparkfun´s link on how to use it (See section "How to Measure Current"):

https://www.sparkfun.com/tutorials/202

Greetings

posted by Ney Palma 31 Mar 2013