Power supply for SIM800

Hi Ravi,

I was looking at SIMCOM800 hardware desing and it includes a power on sequence.
I was wondering if I buy aGSM modem form market, they don’t do any such power on sequence. Is it ok not to have that?

Hi Dharmendra,
The power on sequence is normally controlled by an MCU using the PWRKEY pin. Some boards come with auto power on which just hold the PWRKEY pin to ground on boot up. So it depends on where you are interfacing the SIM800 to.


i have made one GPS tracker using arduino and sim808 ,it’s working file with 5v and 1amp supply,but when i have connect this device direct to car battery through 12v to 5v converter voltage regulator 7805 so when we pressing horn so fluctuation is going and device getting restart. so what i have to do for making power supply and which capacitor i need to use across input and output of 7805 voltage regulator ,by which it will not resetting and 3-4 sec power backup will generate.

Thank you…