Hi, I am currently doing a project that involves ESP8266 and SIM900a GSM module.
I tested the system and was able to send SMS to my phone. However on one time, the MAX232 IC on the GSM module suddenly heated up drastically, which I unplugged the SIM900a immediately, after that incident, the GSM module would either have the IC heat up or successfully send the SMS, there were no changes other than plugging and unplugging the power supply. I would like to know any possible causes that would cause this.
Here are the connections:
Vcc and Gnd -> External power supply 5v 2a
3VT and 3VR -> D7 and D8 (I'm using Software Serial)
SIM900a GND -> ESP8266 GND
Please post complete schematics. Pen and paper is usually good enough.
Could You provide a link to the datasheet for the board equpped with the SIM900A module?
I am assuming these are the datasheets you are looking for?
NodeMCU 1.0 ESP-12E
0A-ESP8266__Datasheet__EN_v4.3.pages
SIM900A
SIM900A-Datasheet.pdf
Good!
The first glance show Vbat maximum is 4.5 volt. Applying 5 volts might be the reason for the problem.
I need more time to check things up. The bus is leaving shortly.
Page 17 in the datasheet shows data for both Vbat and Vrtc. Consider them.
Page 22 suggest a powersupply for the board.
Figure 4 shows additional data.
Section 3,3,1 tells important things.
Check page 24, "Hardware design"
Page 33 shows the serial connections.
Some things to consider....
This might be a speculation, but when I connect the 3VR pin to D8 after the GSM module is powered and has signal, it would not heat up and the SMS is sent out. Not sure if there's any correlation though but I tried a few times and it did not heat up.
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