I have a circuit composed of Arduino Mini Pro 3.3V and GY-GPS6MV2 (GPS Ublox NEO-6M). I have tried to power it with 3 different sources:
- 3xAA NiMH in serie connected to RAW pin of Arduino and using its VCC pin to power GPS
- DC/DC Step-up power converter powered by 2x2 serial-parallel NiMH AA connected to VCC of the Arduino
- (high current) USB via FT232RL FTDI 3.3V
If GPS module is not attached then measured VCC is in all three cases almost 3.3V but once I attach the module then it drops again in all cases to around 3.0V (it varies a bit depending on how much current does GPS module just need).
If I was powering it with USB then in some cases GPS module was restarting repeately because it had not enough voltage. I've fixed this by bypassing built-in voltage reglator of the GPS module.
Input current of the GPS module is measured max 70mA which I think is not that much. Input current of the whole circuit is then around 100mA (so it is 30mA for Arduino + some other parts).
Why is there that big voltage drop and why I observe it in all three cases? I don't think that 100mA is that big current for any of the three powering solutions.
Answer
My circuit is built on breadboard. I have found out that breadboard itself has pretty high contact resistance and this is one of the main reasons of the voltage dropout when supplying power by DC/DC regulator (2).
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