Prevent damaging more SIM800s

Other Hardware General Electronics
1

Hi everyone,
I am going to develop a GPS tracker for cars that sends its location via GPRS, similar to many of the projects available online. I'm using 12v DC power supply, two MP1585 step down regulators (one for SIM800L and one for the other components), an Arduino pro mini, a SIM800L, a Ublox Neo 6m and a few other smaller components.

I placed each component in the circuit and tested it alone (along with the regulators). Vcc voltages of all components were in the suitable ranges, they all turned on and were fine.

After a while for the second time, I placed SIM800L and MP1585 in the circuit and it did not turn. While the DC power supply was turned on, I measured the voltage between the Vcc and Gnd pins of SIM800L. It was 0.4v! I quickly turned off the power supply. However SIM800L seems damaged as multimeter says the Vcc and Gnd pins have been shorted.
I checked the circuit for another time. I found no errors but a few doubts. Can any of the below be the cause of this event?

Thank you

  1. I connected power supply leads to regulator input by hand and there were some small sparks.
  2. I've connected the Vcc and Gnd pins of SIM800L by a 1000uF capacitor.
  3. I used an Aluminium electrolytic capacitors as did not knew I must use the ones with a low ESR.
  4. I used a multimeter while the circuit was on.
  5. I used a multimeter in the continuity mode to test if any of the SIM800L pins were shorted.
2

GSM modules assume 3.7V LiPo cells for power, and pull large current spikes (over 2A). If the supply wasn't able to do that the module or the supply are likely to shutdown.

The MP1585 seems only to be rated 2A or so, so will probably be tripping out sporadically with a phone module
(the current draw is determined dynamically by the module according to signal strength reports, and is very spikey so cannot be measured with a multimeter at all).