Seeeduino MEGA: The 3V3_VCC_5V switch


What the main “function” of this switch? It is supposed to change the reference voltage for the AD conversion?
When I switch it to 3V3 the conversion of 3.3v is not 1023!



PS.: Sorry for my bad English.

I too wondered what the purpose of the 3.3/5 volt switch was. After reviewing the schematic, it is only to change the voltage applied to the AVCC pin of the processor, which is used to set the upper range reference. I tested mine and I do get 1023 counts if I apply 3.3 volts to the analog input pin with the switch in the 3.3 volt position. Of course when the switch is in the 5V position, 1023 counts requires 5 volts to the analog input pin.

So what counts are you getting? Have you measured your 3.3 volt pin to see what it’s actual voltage is?


Ok, the problem is that the 3v3 “reference voltage” is @ 4.10V when the switch “3V3_VCC_5V” is on 3V3… :confused: