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I know there is a similar question but it did not solve my doubts, I will be clear and concise.

I recently bought the SIM800L module and then I started to try it, at the beginning it restarted itself and I realized it was due to voltage problems. After this I decided to make my own voltage regulator, using an LM317T and some other components. This worked well and placed the voltage in 4v, this way the module stopped re-starting if it was not used with a SIM but if you put one the voltage went up and down and the module was reset logically since its voltage parameters were exceeded. My question is what can I do to have a stable voltage? And if this will be my problem?

I made a video to show the problem, from minute 2:30 I put the SIM.

This is the regulator diagram: enter image description here

Thanks in advance!

P.D: The battery provides the required amperage, that is if the regulator can not affect it.

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  • \$\begingroup\$ Connect a capacitor and a 4V Zener diode across Vout and GND \$\endgroup\$ – MaNyYaCk Mar 16 '18 at 5:10
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You can't really read the voltage during the current spikes, the multimeter is not quick enough.

GSM modules induce a large current spike during transmission and even larger during network registration (~2A) for ~500uS. The regulator might not to be able to provide it that quickly. Put a ceramic capacitor (1uF) in parallel with a bigger electrolytic one, like 1000uF on the output. Don't forget to put them as close as you can to the module's pins, especially the smaller one. Good jumper wires will help too. Not sure why it goes up to 5v though, you might want to try to use a different regulator/power supply. If you're using a 3.7V lithium battery, you can just feed the module directly without the regulator.

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the solution is simple. The module is poorly designed to run from other sources than the battery. There are 2A spikes at the VCC level. Changing the C3 capacitor will most likely fix module from restarting. I used 2200uF cap, but try experimenting with less capacity. I just had this one at reach.

Connect the capacitor as pictured

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