Sim800 power isolation

[aiannar974]

Hello Everyone- I have a project where I will be using an Arduino to let a process run and then send an sms to log who triggered the process.  I know the sim800 draws a lot of current.  I plan on using a 5v 3A power supply.  When the sim800 kicks in, will this effect the Arduino?  Both will be on the same supply.  The Arduino is not posing the Sim800.  Do I need any to make sure I do not hurt one of the pieces in the circuit?

Thank you,
Anthont

[SteveMann]

5V would be too much for the SIM800 which wants a low of 3.3v, nominally 3.7V.
If you have a decent supply than the high-current burst of the SIM800 should not be a problem.  The worst that can happen is a reboot of the Arduino. If that happens put something like a 47uF capacitor on the 5V pin of the Arduino.

[aiannar974]

Great - thank you for the help

[chopsuwe]

If you do have problems add a large capacitor in parallel with the SIM800 power pins, as close to the module as possible. Around 1000uF should do.