Lowering Voltage to 3.3 from 5

[copterrichie]

I heard one way to reduce voltage from 5 to 3.3 volts is to use a 1K resistor, is this true?

[tovrin]

any voltage divider circuit would work. generally requires 2 resistors.

[copterrichie]

Thank you.

[QuadBow]

I heard one way to reduce voltage from 5 to 3.3 volts...

The topic is more complex. Therefore, my question is: why do you need to lower the voltage?

[copterrichie]

I heard one way to reduce voltage from 5 to 3.3 volts...

The topic is more complex. Therefore, my question is: why do you need to lower the voltage?

I have a device that requires 3.3 volts power supply but the Arduino output 5 volts. I will use a 3.3 voltage regulator to error on the side of being safe. Thank you.

[Peter]

To lower voltage of power supply you need a voltage regulator. If you want to convert a signal from an high voltage you can use a voltage divider. A voltage divider would prevent current flow in the power supply scenario.

In an other thread it was was mentioned you could just use a resistor on the signal wire to prevent current flow. I have to sort out if that works in every situation.

[QuadBow]

I have a device that requires 3.3 volts power supply but the Arduino output 5 volts.

Are you talking about an I2C device?
They should be 5V compatible. You only have to take care not to mix up 3,3V and 5V i2c-devices at one i2c-bus and not to switch on the internal pull-ups.

In case you have to mix up 3,3V and 5V i2c-devices at one i2c-bus you have to connect a special chip in between.

[EOSBandi]

I have a device that requires 3.3 volts power supply but the Arduino output 5 volts.

Are you talking about an I2C device?
They should be 5V compatible. You only have to take care not to mix up 3,3V and 5V i2c-devices at one i2c-bus and not to switch on the internal pull-ups.

In case you have to mix up 3,3V and 5V i2c-devices at one i2c-bus you have to connect a special chip in between.

Or a fet and two resistors per line.... resistor based voltage divider is not recommended on I2C bus. Schematic is here : https://www.sparkfun.com/datasheets/Bre ... er-v10.pdf use the TX part only..... (or but this blob from sparkfun it's 2usd)

[copterrichie]

Are you talking about an I2C device?
They should be 5V compatible. You only have to take care not to mix up 3,3V and 5V i2c-devices at one i2c-bus and not to switch on the internal pull-ups.

In case you have to mix up 3,3V and 5V i2c-devices at one i2c-bus you have to connect a special chip in between.

What I am actually doing is, connecting a USR-WIFI232-X to the Arduino serial port. Reading the manual of the USR-WIFI232-X, the power supply voltage does not appear to be 5 Volt tolerant. I did not think about using one of the Sparkfun logic leveler which I have two just sitting around. Thank you EOSBandi.

[copterrichie]

Here is what I ended up doing because the Sparkfun logic leveler does not supply 3.3volt power.