TM4C129ENCPDT: Relay circuit interface with TM4C129ENCPDT microcontroller

Nishitha Chandrasekar

Intellectual 700 points

Part Number: TM4C129ENCPDT

Hi Sir,

I need to interface 6v relay with 3.3v output signal of microcontroller (TM4C129ENCPDT)

over 6 years ago

0 Charles Tsai over 6 years ago

TI__Guru**** 182626 points

Hi,
The microcontroller output is only 3.3V. If you need to interface with a 6V component then you will need to have a level shifter. You might want to start with the below TI link for level shifter or go to mouser/digikey for level shifter that is suitable for your applications.

www.ti.com/.../overview.html
www.mouser.com/.../74VHC4316-29600.pdf

0 Nishitha Chandrasekar over 6 years ago in reply to Charles Tsai

Intellectual 700 points

Hi Sir,
I have a doubt, based on 3.3v relay output trigger pulse whether TM4C129ENCPDT microcontroller can able to act as a input to generate a count

0 Genatco over 6 years ago

Guru 55553 points

We use a digital NPN switch made by none other than Diodes Incorporated.. They have several different ones to choose in datasheet.

0 Charles Tsai over 6 years ago in reply to Nishitha Chandrasekar

TI__Guru**** 182626 points

I'm not so clear with your setup. Are you receiving an 3.3V signal from the relay? If yes, then the MCU can receive it. Please go the device datasheet electrical section and make sure your input meets the MCU GPIO input electrical characteristics.

0 Charles Tsai over 6 years ago in reply to Charles Tsai

TI__Guru**** 182626 points

Hi,
I didn't hear back from you. Is the problem resolved? I will close the thread for now. If the problem is not resolved you can reopen this thread or if you have new question please open a new thread.

0 Nishitha Chandrasekar over 6 years ago in reply to Charles Tsai

Intellectual 700 points

yes i am receiving 3.3v signal from the relay.
I need to help how to make a circuit 3.3v signal from the relay

0 Charles Tsai over 6 years ago in reply to Nishitha Chandrasekar

TI__Guru**** 182626 points

Hi,
I already mentioned that the MCU requires 3.3V input. If your signal input is higher than 3.3V then you need to add a level shifter. If your input is already 3.3V then you can connect to the MCU provided that your signal also meets the Vih and Vil of the input pin as shown in the datasheet. Perhaps I'm not understanding what you are asking that you need to make a circuit 3.3V signal from the relay when you already said you are receiving 3.3V from the relay. Maybe you can draw a diagram to illustrate.

0 Nishitha Chandrasekar over 6 years ago in reply to Charles Tsai

Intellectual 700 points

Hi Sir,
I have a doubt, if I am sending 3.3v signal to my MCU GPIO port pin - shall we do like that?
whether there is any constraint for current because in datasheet they has mentioned that it can sink or source certain amount of current what happened when we connect 3.3v (+ ve) wire directly to GPIO pin

0 Charles Tsai over 6 years ago in reply to Nishitha Chandrasekar

TI__Guru**** 182626 points

Hi,
What type of relay do you have and how are you using the relay in your application in conjunction with the MCU? Normally the MCU will drive the low voltage trigger input of the relay to energize the coil as to turn on the mechanical switch for the high voltage/current side. However, in your usage you are taking the relay output back to the MCU. I'm not clear with your application if you mind to elaborate.

0 Nishitha Chandrasekar over 6 years ago in reply to Charles Tsai

Intellectual 700 points

Hi Sir,
My application is a discrete signal, Input side 24vdc but we could not able to communicate that, so using relay it will convert to 3.3v based on that signal i would like to increase the count to display in LED display

0 Charles Tsai over 6 years ago in reply to Nishitha Chandrasekar

TI__Guru**** 182626 points

Have you considered a voltage divider using resistors? What is the relay you are using? If its output (connecting to the MCU) meets the MCU's IO operating characteristic then it should be fine. So please check your relay datasheet.

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TM4C129ENCPDT: Relay circuit interface with TM4C129ENCPDT microcontroller