Analog Signal scaling both directions

Using Arduino General Electronics
#1

Hi,
I'm looking for a solution that can scale a 0-5v Signal to 0-3.3v and also the other way around.

I read quite a lot actually about op amps, but still the question remains about scaling in both directions.

Basically I'm looking for a bidirectional logic level shifter for analog signals.

Is this possible ? Does somebody have schematics, maybe on easyeda?

I'm thankful for every help that I can get. Meanwhile I will keep reading about the functionality of op amps and what can be done with it.

Regards !

#2

Basically I’m looking for a bidirectional logic level shifter for analog signals.

A logic level is not analog.

Are you trying to turn a 0…5V analog voltage to a -3.3V…+3.3V signal?

#3

I know that logic level is not analog, but I mean functionality wise it's basically the digital thing of what I want to do.

I want to scale 0-5V to 0-3.3V and the other way around.

0-5v -> 0-3.3v
0-3.3v -> 0-5v

#4

Probably the best way to do this is with an Op Amp–like this:

OpAmp_3.3V_to_5V.png

OpAmp_5V_to_3.3V.png

Caveats:

  • Those resistor values might need to be different, depending on the application.
  • This assumes a frequency less than, probably around 500kHz.
  • The Op Amp supply voltage needs to be at least 1.5 to 1.75V higher than 5V [depending on how much current the Op Amp output needs to deliver [up to 5mA]. I indicated 12V, but it doesn’t need to be that high – but, the Op Amp will perform better at higher voltages [only a concern if you plan to push it to it’s limits]. I would use a voltage of at least 7V
  • The Op Amp of choice must include Ground in it’s Common-Mode Input Voltage Range.
  • The 0 - 5V to 0 - 3.3V case can be, in some cases, merely the voltage divider [i.e. R1 & R2]. The Op Amp provides buffering. And, buffering makes it possible to connect it to a lower impedance load, without the voltage sagging.
  • Hmmm…what did I forget…?
#5

Hi,
Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html .

What controller are/will you be using?
What is the application that needs the signal translation?

Thanks.. Tom.. :slight_smile:

#6

Kurtisane:
I want to scale 0-5V to 0-3.3V and the other way around.

But not fast, right?

#7

Kurtisane:
0-5v -> 0-3.3v

Very simple: use a voltage divider. 10K + 5k1 will do great.

0-3.3v -> 0-5v

Use an OpAmp as suggested in #3.

#8

wvmarle:
Very simple: use a voltage divider. 10K + 5k1 will do great.

How can you be sure? The OP has given us no particulars. If the 0-3V must drive a low impedance, this load may alter the voltage levels on your voltage divider.
That's why I included a buffer on the output of the voltage divider, with a note qualifying it as optional, and indicating the possible inadequacy or even that. In fact, some sort of Power Amplifier may be needed--who knows?!

#9

Kurtisane:
I know that logic level is not analog, but I mean functionality wise it's basically the digital thing of what I want to do.

I want to scale 0-5V to 0-3.3V and the other way around.

0-5v -> 0-3.3v
0-3.3v -> 0-5v

Please be specific: do you want to level shift a logic, digital signal? Or do you want to scale an
analog voltage.

These are done two entirely different ways.

#10