Hello,
I bought BT module BTM-112 working at 3.3V. Although Arduino has both 5V and 3.3V power output I need to switch between 3.3V and 5V, so I made a voltage divider from TTL 5V to CMOS 3.3V on serial link with R1=1.8k an R2=2.2k and the same divider on power line. Voltage divider on serial link works fine, but on the power line is low voltage. When I replace 2.2k by 3.9k (R1=1.8k, R2=3.9k leads to ground) is 1.7V? How is it possible, when Uout=R2/(R1+R2)*Uin? What values of resistor should I use?
Thanks.