Arduino Nano 33 BLE Sense with 5V components - circuit questions

Projects General Guidance
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Hi Everyone,

I'm working on a project with the Arduino Nano 33 BLE Sense at the moment and designed a circuit in Fritzing for it.

When somebody presses the button the servo motor should be triggered and a variable should be counted up and be displayed on the 7-segment-display (multiplex-cathode). The potentiometer should be used to adjust servo power.

It's been a while since i worked the last time with microcontrollers and I never worked with a 3.3V sensitive controller. It would be awesome if you could answer following questions:

  1. Is it safe to feed the GND of the 5V circuit back into the Nano 33? (Since it's GPIOs are 3.3V only - I would activate the 5V output of the Nano and would use the second available GND to feed it back in.)

  2. Can I safely connect 3.3V GPIO outputs to the servo motor control pin and the bit shifters clock etc.? Those components run on 5V but I figured that only GPIO inputs from 5V would damage the board?

  3. Do i need some additional resistors between the 7-segment-display and the TPIC6B595 bit shifter drain pins? I've seen both actually, resistors before the display (for the A,B,C,D,E,F,G pins) and after the display (for the DIG 1, DIG 2, DIG 3, DIG 4 pins).

Thanks in advance!

Bildschirmfoto 2021-06-22 um 19.52.01
Bildschirmfoto 2021-06-22 um 19.52.011834×1204 504 KB

2

Please post a real wiring diagram. I don't have those circuits and can't identify the pins. Fritzing are paintings, childrens play.

  1. What are You trying to tell? Make it a wiring diagram.
  2. Read the data sheet for the 5 volt stuff and check if 3.3 volt is good enough. Never feed 5 volt signals to the 3.3 volt controller pins.
  3. Read the data sheets of the TPIC6B595, especially the application notes.
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No, it should not.

Go away and learn about servos.

a7

4

That's a 5volt-only chip, including logic signals.
Leo..

5

Thanks! Cut, paste and Google is not my favorite using the phone....

6

What a toxic forum.

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Welcome to the forum.

Do you think you can insult old grumpy guys using the word toxic? We are here to help and sometimes you get some patt on the back for doing/saying something foolish.

Unfortunately, Fritzing pictures are nice to look at but they are only good for beginners to take some ready component and wire them up. The electronics world uses schematics. That is the universal language of circuits. A hand drawn schematic is better than a Fritzing picture.

In most cases you can connect grounds. Just like you can stand on the same ground that is the reference to the voltage coming out of your wall socket. There are exceptions when it comes to very sensitive signals. Then the ground needs to be connected in a way that the return currents of power circuits do not disturb the measurement of sensitive signals.

When you combine 5V and 3.3V systems you need to read the datasheets. Some circuits have tolerant pins otherwise use level-shifters. Level-shifters are not just to avoid damage. If the driving circuits creates a logic-high voltage that is too low for the input the circuit may not work or be unreliable. This can happen at a point where you do not even think about the voltage levels anymore. I was kicking myself when I found that out. :slight_smile:

I am not sure what you mean with that. Connect the ground of the Nano with the GND of the 5.5V circuit. Use level-shifters for the signals. Do not use the power of the Nano for anything but some small sensors and some buttons or switches. Everything else should be powered by a separate supply.

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