Hi - new to the forum. Very much appreciate the wealth of knowledge here!
Simple question:
I am working on a project, in which a breakout board needs separate power supply, and this needs to be 3.3V. My power supply for the project is 5V, so I figure I need a level changer for this particular component. I know how to make a two-resistor voltage divider to bring the voltage down, but I was looking at the commercially available multi-channel level changers, since they would do the trick simply and efficiently. However, when I read the instructions, it states that the level changer needs 5V at the high side and 3.3V on the low side ("as reference"). My question is this: Does this not defeat the purpose? If I already had a 3.3V power option, I would simply use that?!
"The level converter is very easy to use. The board needs to be powered from the two voltages sources (high voltage and low voltage) that your system is using. High voltage (5V for example) to the ‘HV’ pin, low voltage (3.3V for example) to ‘LV’, and ground from the system to the ‘GND’ pin."
What is the use if I need to give it the 3.3V that I need in the first place?
Level shifter is for converting signal lines between different voltages - you still have to supply power at the two voltages. It is not the same as a regulator or other power supply, which supplies power at the appropriate voltage.
DrAzzy:
Level shifter is for converting signal lines between different voltages - you still have to supply power at the two voltages. It is not the same as a regulator or other power supply, which supplies power at the appropriate voltage.
Different tools for different applications
Ok - I think I see the difference. However, my application is exactly that: shifting a serial signal voltage. The GPS unit I am working with has 5V Tx, but only 3.3V Rx (as seen from the GPS board). Therefore I want to shift the Arduino Tx (i.e. the GPS Rx) signal from 5 to 3.3V. If I use the sparkfun board linked to by vffgaston, I need to supply a 3.3V voltage from somewhere else, whereas if I create a voltage divider myself I don't. I found that strange..
Paul__B:
Sorry, there is an important rule here:
If you do not specify - with Web links preferably - exactly what components you are wanting to use, you cannot get a useful answer.
OK, well if you only need to level shift in one direction - downward - and your source is an Arduino then you can use a divider with relatively low values to achieve full speed - perhaps 560 Ohms in series and 1k to ground.
An alternative is to use a 1k in series, and a diode from that input to your 3.3 V supply. You will always have the 3.3 V supply handy since the level shifter is always wired directly at the input of the device which it is feeding.