Battery pack to power GSM, GPS, servo, loadcell, fingerprint, keypad, and lcd

Using Arduino Motors, Mechanics, Power and CNC
1

Hi. I'm new here. I'm making a project using an atmega328 microcontroller with the components stated above. I plan to power all these devices with one rechargeable battery pack that will allow the system to last for 2 days.

This is my tentative design for a 12v supply for testing my system:

  1. I will connect the servo motor, load cell, gps and gsm to an SPX2815 low drop out voltage regulator to draw 5v from the supply.
  2. The fingerprint reader will be connected to a separate SPX2815 to draw 3v from the supply.
  3. The microcontroller will power the lcd and keypad and will be connected to a LM7805 regulator.

What battery pack should i use? What capacity should i use that will last for 2 days?

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2

Without knowing even remotely what the current draw is it's going to be hard to say. Also, is there a space limit for this battery?

You'll also be wasting a fairly significant amount of power using linear regulators, especially if you're looking at 12v feed. Do you actually have something that needs 12v? If not I'd be looking at some of the 2S Lipo packs from the R/C stores. Something between a 2200mah and 5000mah pack will probably get you somewhere close, but that's very much a guess.

I would expect the biggest power draw will be the LCD backlight so you can probably make some savings by managing when the backlight is on i.e. turn it off 30 seconds after the last keypress

3

What will happen to your five volt supply if the gsm modem tries to draw 2 amp? In addition to the power that the other peripherals are using?

4

I don't know how much current my whole system draws. Yes there is a space limit for the battery, approximately 21 sq.inch.
I don't really have something that uses 12V. I just want something that's rechargeable and can power my system for 2 days.

5

dannable:
What will happen to your five volt supply if the gsm modem tries to draw 2 amp? In addition to the power that the other peripherals are using?

Im supplying it with an external power supply at the moment. I'm wondering if a 12V rechargeable battery pack is better than 12 1.2V NiCad rechargeable batteries soldered together. Or lighter. I want something that will not weigh too much.

6

If you have it mounted and powered by power supply already you should measure current draw whkile putting the system through all it's functions. See the average and max current draw.