5v instead of 3.3v

Hello, this is a noobish question but i have an Arduino Pro Mini 5v and i want to connect a Rayson BTM-182 module which feeds with a 3.3v supply. I am no expert so i would like to know what are the consequences of feeding with 5v instead of 3.3v.

Thnx.

what are the consequences of feeding with 5v instead of 3.3v.

Unexpected failures, shortened life, overheating...the usual.

Thank for reply. One more doubt... would it be possible to supply 3.3v forming a potential divider? for example a 150 resistor at the top and 300 resistor at the bottom (resulting in 3.333v)? If so would it look something like this:

Pro Mini 5v BTM 3.3v GRD-------------------GRD TX---------------------RX RX---------------------TX VCC---150R-----300R--GRD | ----- VCC

rinator: Thank for reply. One more doubt... would it be possible to supply 3.3v forming a potential divider? for example a 150 resistor at the top and 300 resistor at the bottom (resulting in 3.333v)? If so would it look something like this:

Pro Mini 5v BTM 3.3v GRD-------------------GRD TX---------------------RX RX---------------------TX VCC---150R-----300R--GRD | ----- VCC

No, because the load resistance of the Rayson BTM-182 attached to the VCC point on your divider changes the parameters of the whole calculation. Proper way is to use a small 3 terminal fixed 3.3vdc regulator to cut down the 5vdc to 3.3vdc for the Rayson BTM-182. http://parts.digikey.com/1/parts/1101885-ic-reg-ldo-lp-100ma-3-3v-92-lp2950acz-3-3g.html

Your Tx signals will also be 5v and not 3.3v, you will fry your module even if you supply it with 3.3v to Vcc

So i will have to use 2 of those 3 terminal regulators then? one on Vcc pin and another on the Tx pin? Thnx

another on the Tx pin?

No, you don't use a regulator for changing signal levels. You use a transistor or two.

As Mike says, you need to understand the difference between power supply level and signal level.

You need the regulator for power supply. There are then numerous options for signals. If you have a 5v signal going into a 3.3v device, a potential divider will probably work. Alternatively, a transistor or a mosfet. In the opposite direction (3.3v signal into a 5v device), in theory, the 3.3v is enough to give a logic high - it's 66% of 5v after all.

If all else fails, have a Google for 'mosfet level shifter' or 'signal level shifter' - or buy the board of a similar name from Sparkfun.

Thanks for the replies now i get the idea. So could this be a solution then? http://www.sparkfun.com/products/8745

Thnx

Yes, together with a 3V3 low-dropout regulator. Its a shame that board doesn't have one on it (except it can work at lower voltages too).

(except it can work at lower voltages too).

True but it might not work at 16MHz at a voltage of 3v3, but then again it might just but it is outside the recommended operating conditions. However it is not harmful to try.

Why not just use the 3.3V cpu instead of the 5 volt one? You're jumping through a lot of hoops just to use the wrong part.

Then throw a LiPo battery and a charger on there and call it a project.