Logic Level Shifter or not?

D

Digl

New Member

• Apr 10, 2020

• #1

Hi,
I am a total noob in this area so please forgive me if my question is total nonsene!
I want to substitute a button on a board with gpio from a nodemcu (3.3V) - the button is wired with 2 wires and uses 5V.
In a nut shell, I want to be able to control the "button pins" with the nodemcu.
I read that the nodemcu might be able to tolerate 5v on the pins - but that is probably not a nice solution.
Can this be done with a Logic Level Shifter (I have a bidirectional LLC with LV,GND and LV1-4 on one side and the same for higher voltage (HV) on the other)?

Best Regards,
Digl

 

V

Visitor

Well-Known Member

• Apr 10, 2020

• #2

The official word from Espressif (makers of the ESP8266 used in the Node MCU) is that the digital pins are 5 volt tolerant, so you shouldn't have any problems at all.

 

S

sagor1

Active Member

• Apr 10, 2020

• #3

Yes, that should work. Those level shifters are usually bi-directional, but you can run them in one direction only if you wish. I use one module to interface a GPS serial (3.3V) to an Arduino (5.0V). Serial really only runs one way, but like you say, why risk having 5V on a device that expects 3.3V, even if they are "5V tolerant"

 

D

Digl

New Member

• Apr 10, 2020

• #4

Thanks for the quick answers, I guess I could just use it without the LLC.
I would just like to know how I would have to wire it, because I'm interested.
Is my wiring in the attachment false?
I only have two wires from the button...
Thank you very much!

 

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sagor1

Active Member

• Apr 10, 2020

• #5

You have to wire in the LV (3.3V) and the HV (5.0V) as well. It won't work without the voltages and grounds. Grounds can be connected together (usually they are)

 

P

Pommie

Well-Known Member

Most Helpful Member

• Apr 10, 2020

• #6

Why can't the button use 3.3V? Button between pin and ground and a pullup resistor to 3.3V.

Mike.

 

gophert

Well-Known Member

Most Helpful Member

• Apr 10, 2020

• #7

Don't complicate your life. The esp pins can handle 5volts.

 

D

Digl

New Member

• Apr 11, 2020

• #8

Hi!
Since I don't have have a power pin on the board with the button, I will not over complicate it and just use it directly.

I didn't want to use 3v on the button because it controls a relay and I wasn't sure if the relay would trigger with 3v...

Thank you all for your help!
Happy Easter

 

gophert

Well-Known Member

Most Helpful Member

• Apr 11, 2020

• #9

If you don't want to put 5v on the esp pin, you can use code to translate the button press to a transistor base to drive your relay.

 

Last edited: Apr 11, 2020

crutschow

Well-Known Member

Most Helpful Member

• Apr 11, 2020

• #10

Make sure there's a transient-suppression diode (e.g. 1N4148) across the relay coil (cathode to positive).

 

gophert

Well-Known Member

Most Helpful Member

• Apr 11, 2020

• #11

crutschow said:

Make sure there's a transient-suppression diode (e.g. 1N4148) across the relay coil (cathode to positive).

Click to expand...

fixed - thank you.