I am using a sim900 module in the following link and I connect it to my laptop using USB to TTL converter and the module works properly. But, when I connect the same module to 9V DC battery the module keeps restarting, and also if I power the module from my laptop via usb cable it also keeps restarting. So, please, help me out.
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\$\begingroup\$ yeah i think it is, evelta.com/image/cache/data/Manish/M3/… this is the one im using. But it also restarts when i power it by laptop via usb cable \$\endgroup\$– sp39Commented Mar 7, 2014 at 8:02
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\$\begingroup\$ That's probably only good for 100mA or so. It doesn't have a USB port that I can see are you just connecting to the USB power pins directly? That's only 100mA as well if connected that way. \$\endgroup\$– PeterJCommented Mar 7, 2014 at 8:14
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\$\begingroup\$ I'm just connecting the USB power pin directly. So what can i do to get it to work on battery? \$\endgroup\$– sp39Commented Mar 7, 2014 at 8:18
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1 Answer
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A USB device can only draw 100mA by default, during enumeration you need to request the maximum of 500mA for USB 2 and below during device enumeration. So when connected directly to the power pins you can only draw 100mA. I couldn't see a current specification for that board but most GSM modules are closer to 500mA than 100mA.
For a Energizer 522 Alkaline battery the maximum current draw appears to be around 500mA so that might be one option although the lifetime will be relatively short. PP3 batteries generally don't have very good current draw characteristics, personally I'd probably look at using something rechargeable like 6 x AA NiMH cells, or maybe AAA if size is a bit of an issue. LiPo packs that are commonly used in remote controlled cars etc may be another option.
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\$\begingroup\$ Ill check it out and let you know if it worked \$\endgroup\$– sp39Commented Mar 7, 2014 at 8:37
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\$\begingroup\$ GSM modules that I've used in the past have stated a maximum peak current draw of around 1A. I'd suggest a bank of 6xAA batteries instead of 1xPP3 would be a good starting point. \$\endgroup\$– marktCommented Mar 7, 2014 at 9:41