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Do I need a level shifter or is there an easier way?

Former Member

I'm trying to get an ESP8266 WiFi module working with my Arduino. However, Arduino's output 5v and the ESP8266 needs 3.3v for it's logic. I've heard some people say that the 5v logic scale and the 3.3v logic scale are interchangeable and doesn't matter but others say it could fry your module. So I decided to try to play it safe and ask you guys.

 

So, how can I convert the Arduino's 5v down to 3.3v without lowering amperes because the ESP8266 draws >200mA? Also, I'd prefer not to buy a Level shifter, but if it is necessary by all means I'll get one.

 

Thanks in advance! image

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  • 0 in reply to mcb1

     

    I did actually look into voltage dividers. I did all the math was able to find the right resistor combination (A 1k and a 560) for this project. The math said that with the voltage divider Vout would be 3.2v. (I used this formula: Vout = Vin * (R1/(R1+R2))) Then I looked into the formula for amperes from voltages and found this: Amps = Volts / Resistance (ohms). This said that my 3.2 volts was only 0.003 amps. Which I believe is basically 3mA. And I doubt that would work. image So am I doing this right? Or did I mix something up?

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  • 0 in reply to Former Member

    jacob_pickens

    Jacob

     

    Well done your maths and values are spot on for OUTPUT voltage dividers to stop the ESP8266 being destroyed.

    The datasheets say they are 5v tolerant, but that doesn't mean you should design based on that.

     


    A voltage divider will NOT work if you want to supply power to the ESP8266
    Find a 3v3 regulator that supplies 200mA.

     

    This has some maths but is a better explanation of the effects http://www.pdx.edu/nanogroup/sites/www.pdx.edu.nanogroup/files/2013_Input_output_impedance_9.pdf

     

     

    There is a really quick way with voltage dividers.

    2 equal value resistors give you half the voltage (assuming little current is drawn).

    You can also apply ratios or percentage as well. .. ie 2/3 of total resistance at the top results in 2/3rd's of the voltage being dropped across the top resistor.

     

    Generally with a micro controller a 10k to 47k will safely pull up a pin. Once you get higher than that the chances of stray signals increases.

    Arduino have 100M input resistance http://arduino.cc/en/Tutorial/DigitalPins

     

    The other general rule to ALWAYS keep in mind.

    Never apply a voltage to any pin that is greater than the supply voltage of that device. (unless it is specially designed for it)

     

     

    Good luck looking forward to waht you produce/blog about.

     

    Mark