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I'm working on a prototype product(Wifi motion sensor) that will be powered from a battery source, it has a mega328(arduino bootloader, with sleep mode on and wake on interrupt,and WDT in case it hangs up), a PIR motion sensor , and a CC3000 break out board.

Power saving is done in software, but what type of battery should I use? I initially used 2AA with LT1302-5 boost converter, but I think it was not able supply enough current for the CC3000 module, it could not start the SSID scan also the LED on the break out board dimmed out a bit.

Now I'm thinking of using 4AA and using a 5v LDO regulator.

How do I go about it?, what other options I have, I need 5V to operate the circuit. I've never designed a battery powered project before. Should I use different type of battery,LiPo perhaps?

Peak current of 150mA is drawn when communication is going on, draws and 10mA when its asleep. Let me know if you need more details.
Circuit Diagram enter image description here The LT1302 IC is soldered exactly as in its data-sheet.
Source code
https://github.com/hemalchevli/Sketchbook/blob/master/PIR_LP/PIR_LP.ino

This is how to looks

enter image description here

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  • \$\begingroup\$ Any chance that you could add your current circuit diagram, there might be some minor problem with your circuit that is causing it to draw more current than you expect. \$\endgroup\$
    – Mark Booth
    Sep 20, 2013 at 17:59
  • \$\begingroup\$ CC3000 can draw up to 300mA at times, perhaps at startup. I would design with a larger booster. \$\endgroup\$
    – Gustavo Litovsky
    Sep 20, 2013 at 19:04
  • \$\begingroup\$ @ Mark Added the circuit diagram, @GustavoLitovsky I didn't see that spike, perhaps my multimeter is not fast enough, can you suggest the lager booster IC? \$\endgroup\$
    – Hemal Chevli
    Sep 21, 2013 at 5:45
  • \$\begingroup\$ @HemalChevli: You will only see it on an oscilloscope as a dip in voltage if you don't have enough current to the device. \$\endgroup\$
    – Gustavo Litovsky
    Sep 21, 2013 at 14:56
  • \$\begingroup\$ Just a general comment, that a AA is good for ~ 2500 mA/Hr, so 2 of them will be good for 5000 mA/Hr. If you're currently drawing 10 mA in sleep mode, then you'll have about 3 weeks of battery life if all this does is sleep. Any actual motion sensing and communications will decrease this, possibly substantially. Do you have any battery life requirements? \$\endgroup\$
    – rfdave
    Sep 22, 2013 at 1:50

1 Answer 1

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You need to be certain on your voltage and current specifications.
You say 150 ma peak load.

If properly configured The LT1302-5 will easily meet your stated need. If it is failing to do so there is either something wrong with your circuit or your load is far greater than you state. The Digikey parametric selector suggests that there are 150 mA and 600 mA Iout versions but this does not appear to be suppoted by the datasheet.

The LT13o2-5 will provide up to 600 mA at 5V out. The graph below (from page 1 of the LT1302 data sheet shows that peak efficiency with vIN = 2v is achieved at Iload ~= 200 mA - above your stated requirement. and they show results up to Iout = 600 mA.

The battery current will be ~+ Iout x Vout/Vin x 1/Z
where Z = converter efficiency (0 <= Z <= 1).
For say 80% efficiency, 2V in and 5V out and 150 mA load, I battery
~= 150 mA x 5V/2V x 1/0.8 =~ 500 mA.
That is well within the capabilities of Alkaline AA cells or of rechargeable NimH cells.
Battery life at 150 mA ~= Battery_Capacity / Battery_Current x K
where K is a derating factor 0 ...1 which drops as load increases and as the battery is used (due to rising internal resistance).

enter image description here

4 x AA cells will provide 5V for only a small part of an Alkaline battery's life and not at all with NimH.
5V/4 = 1.25V
You need at least 1..25V/cell to regulate it down to 5V. Alkaline and Nimh can be considered to be 'dead' at 1V.
So 5 cells and an LDO (low dropout regulator) would be a minimum.
Valkaline_new ~= 1.65V, so initially 5 cells would give you 1.65 x 5 = 8V +.

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  • \$\begingroup\$ Yes, I was very confident that it will work with LT1302-5 because, it works perfectly fine with the USB port that supplies max 500mA, I measured the current with my analog multimeter, I'm using CC3000 breakout board from adafruit, and they also said it consumes about 130mA when communicating to router. The PIR sensor take few milliamps, so I'm quite sure about the load. \$\endgroup\$
    – Hemal Chevli
    Sep 20, 2013 at 13:00

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