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Thread: Output 0-5v vs 0-3.3v

  1. #1
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    Output 0-5v vs 0-3.3v

    Hi all,

    I've used the search to find the answer to my question, how can I output up to 5v with e.g teensy 3.2. The answers I found were for the most part to fix the problem of e.g. driving a motor that needs 5v as input voltage. From what I understand you could use a boost converter for that (it will boost the 3.3v to 5v.). Example https://www.ebay.com/itm/DC-DC-Boost...UAAOSwjVVVwi5p

    What I need is an output voltage range of 0-5v instead of a range from 0-3.3v. Is this what the boost converter would do as well? Or will it always try to boost the input up to 5v?

    I know how to step down voltages with a circuit, but have never stepped up the voltage range. I am trying to build a simpe circuit that can be used in modular synths, focused on pitch control. Those synths usually expect a voltage between 0-5v for the full pitch/note range.

    Thanks in advance for any tips or guidance!

  2. #2
    Senior Member+ KurtE's Avatar
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    If your circuit really needs a 5v output, you may need to use some form of level shifter.

    There are many different varieties of level shifters, as no one shifter is perfect for all cases.
    Some or one direction (Input or Output), some are bidirectional. Some work well with SPI or I2C and others don't...

    Here are a few examples of ones out there:
    https://www.sparkfun.com/products/12009
    https://www.sparkfun.com/products/11771
    https://www.sparkfun.com/products/11955

    https://www.adafruit.com/product/757

    ...

    Note: The Teensy LC has one pin that a output only level shifter was added, as to make it easier to talk to some devices like NEOPixels.

    Hope that helps

  3. #3
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    Thanks for your answer! I had a look at these. Maybe my question (or application) was not clear enough. At least the first sf board is talking about digital only, and another only works in a range form 1-5.

    From what I understand from my modular friends the synthesizers expect an analogue signal - just a voltage - from 0-5.. Essentially I am looking for the reverse of a resistor, to map the 0-3.3 volt to 0-5v, linearly. Is that even possible?

    Maybe that is exactly what the voltage level translator does, but then it's only working for the 1-5v, or 1.8-5.5, like this one https://www.sparkfun.com/products/11955 - if that is the limitation then I'd just need to work around that, but I want ton be sure I am asking the right question here.

  4. #4
    Senior Member+ KurtE's Avatar
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    Hopefully someone with more current electronics experience will chime in.

    The TTL level shifters are good that if for example you have a signal that is either 0 or 3.3v and you want it to output something like 0 and 5v... That is shift digital voltages on/off voltages.

    If however you are wanting to scale an analog signal that now goes between 0-3.3v to scale up from 0-5v... My guess is some form of op amp

    Maybe something like in: https://electronics.stackexchange.co...-3-3v-to-0v-5v

  5. #5
    Member propa's Avatar
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    You'd need a rail to rail op amp, powered from 5v usb, or 5v from modular. You could use a transistor, but not sure the response would be that linear.

    An op amp can be used to add gain to the signal and boost from 3.3 to 5v. I have a similar project where I've taken the 3.3v and boosted using an op amp to 9.9v by setting a gain of three.

    If you're not aware of op amps, in one configuration, you can set the multiplication of the signal through it by changing the values of two resistors.

    Here's a little calculator online to help the process: https://circuitdigest.com/calculator...ain-calculator

    You'd need to figure out what the gain factor would be to go from 3.3 to 5v, but it shouldn't be too hard to work out for you.

    The other caveat about op-amps is usually they're powered with -/+ dual power supplies, so either you need to make a virtual ground, or use the dual rail from the euro rack. Ideally find a chip that will work at lower voltages and also output as close to the input voltage it's being powered from. (I can't remember any off the top of my head, I'm sure a forum member could chime in here)

    I don't know if there is an opposite of a resistor... could it be a transistor in one configuration amplifies current, in one configuration it amplifies voltage. One thing to remember if I'm not mistaken (in op amps and transistor amplification) you can't create a voltage greater than what it's being powered by. You'd need an inductor/coil transformer to do that, and you wouldn't need to boost any signal like that for modular applications. Think boost converters when you need to turn 5v to 50v!

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