external power supply for arduino and sim900d gsm module

Hello! I use 12V, 2A external power supply for arduino. +5V from arduino powers the LCD and a 6V buzzer. I also have a servo motor connected to digital pin 5 of and powers it from another external source which is 6V, 500mA. Of course both GND of servo and arduino are connected.

I'd like to power the sms module using the source from the arduino. Can I just use the Vin and GND pins to connect it to the gms module? I just measured the voltage from the Vin pin and instead of getting 12V I only get 11.40V.

I also noticed that the capacitors slowly get hot after a few minutes! Is it okay?

The 11.4 is due to the drop across the reverse protection diode. If the caps are getting hot that probably indicates a lot of AC ripple on your DC line. Heat is never good.

Can you get a Y-cable and not run the current for the SMS thru the arduino components? http://www.bgmicro.com/ycable21mmpowerconnectorto2-21mmbarrelconnectors.aspx

not run the current for the SMS thru the arduino components?

How's that?

You said it needed 12V, you had 11.4 after the diode. Use the Y cable and give it 12V.

It's ok if its only 11.40V, Im just saying how the voltage drops in Vin.. I'd like to know if its ok to use that 11.40V from Vin to power up the gsm module? If I use Vin as a source to the gsm module, will the current I get still be the same as 2A which is the current rating of the external source?

Got a spec for the gms module?

The power supply won't care how its 24W is split up across the various loads.

Internally the GSM module runs on 3,9 volts or 5 volts, and i'm pretty sure that any low dropout regulator or small switcher will run happily on everything over 6 volts, so 11,40 volts is not a problem in any way.

// Per.

Sir i have 9 V power supply with a current rating of 0.4 A. i tried to split the supply, one at atmega arduino with 9 V, and the other was 5 V which i regulated to supply GSM module. But it didn't work, the GSM module did not turn on. can you help me hoe can i troubleshoot this matter tnx?. :)

A 400 mA supply is NOT enough unless you have a kind of swithcing mode regulator that can transform the high voltage, low current to low voltage, high current.

Try with a 9V 1A supply or bigger.

// Per.