Knockoff Arduino Pro Mini not giving 3.3V

[cslauritsen]

I did my first build using one of the chinese knockoff arduino pro mini 3.3V from aliexpress. During the assembly process I powered the circuit thru an arduino uno connected to laptop USB. It also worked fine from a battery. Now the build part is done, I want to "deploy" the sensor with wall-wart power. On a wall wart, the sensor came up and successfully presented to the gateway. I got one or 2 readings transmitted from the sensor, but almost immediately thereafter, the radio traffic seemed to come to a halt. I noticed this only happened when powering from a wall wart.

I suspected voltage ripple was affecting the radio and noticed I hadn't added a 4.7uF cap to the radio power pins. I added it, but it made no difference. Since it worked fine with battery power or arduino uno power, I did some voltage checks of 2 different cheap pro minis. When fed 5V on RAW, they output something like in the range of 4 to 4.8V on VCC. So I added a spare 3.3V regulator to my build and now everything works fine, even when powered with the wall wart.

Has anyone had a similar experience? Am I missing something--I thought the 3.3V pro minis had a 3.3 regulator on them??

PS The Pro Mini 3.3V from sparkfun I bought a while back ($10/each) puts out a steady 3.3V on VCC.

[gerritv]

I would check the part number on the regulator. Just because it is sold as 3.3V mini doesn't mean that it is :-(
Feeding >3.3VDC to the radio potentially made it give up its magic smoke.

[cslauritsen]

Thanks. I'll try to figure out where the regulator is on these things. It wan't patently obvious to me. Agreed, I may have hosed this radio.

[gerritv]

The regulator has 3 terminals, on one side, 2 on the other. Usually near 2 'large' capacitors