Control push button

[hassna]

Hello, I hope you are doing well.

I am working with TC3X7 Evaluation Board (Application Kit Manual TC3X7 V2.0 (mouser.com)). I would like to control a push button with a take-over relay to release the pushed button via software. My question is: Do the push button and the relay (take-over for the button) need to be connected to the same GPIO on the MCU side or to 2 different GPIOs?

Looking forward to hearing from you soon.

Kind regards.

Hassna

[TBencher]

Hi hassna,

you can nearly do what you want. I would not necessarily connect your relay directly to the MCU.
For the take-over function using one GPIO you would need to bridge the relay with a manual switch 1 (closer) (in parallel)-which is not connected to the MCU) to force the relay contacts closed. To open the circuit again  you would need to implement a second switch 2(opener) in series to that-which is actually a MOSFET etc.- as well. This MOSFET would be directly connected to your MCU. With that you can easily release your pushed button via software.

Hopefully that helps.

Best regards,

TBencher

[TBencher]

Ah,

don't forget to involve at least one of your closer contacts to be in series to your main path. Maybe you should also provide the data-sheet of the relay. It possibly works a bit different as I currently expect. If yes we'll find another solution.

Best regards,

TBencher 

[hassna]

Hello TBencher,

Thanks for your feedback.

For the relay, I am thinking of something like the following item: Harmony_Relay_SSL1A12JD.pdf (distributordatasolutions.com)

For the push button that will be used is like 0900766b810571d0.pdf (rs-online.com)

For your information and regarding my application, it would be a TC3x7 Evaluation Board and power components (relay, load,..). The connection between components is with Din-rail. 

Kind regards.

[TBencher]

Hi hassna,

hopefully I've got that right now. You want to switch something with a voltage from 24V.
With turn over you mean actually that once you've pushed your button the circuit closes and the solid state relay should keep it closed. If you push your button again the circuit should open.? For this I would suggest you using
two GPIOs as well as an internal small state machine.

Best regards,

TBencher

[hassna]

Hello TBencher,

Thanks for your feedback.

Well with the turn over, I mean actually that once I would pushed the press button, the circuit closes. The idea of using the solid state relay is to release the pushed button by SW when it is needed. The push button is also connected to a 24V relay and load. My question is if I need to connect the relay and the push button to different GPIOs (Please see attached) or just to a one GPIO? 

Kind regards.

[TBencher]

Hi hassna,

two possibilities.

1. With one GPIO: Pushbutton connected to e.g. +5V and to an additional external e.g. transistor as switch, which is then connected to the load at output side and controlled by just one GPIO from MCU

2. With two GPIOs: Pushbutton connected to e.g. +5V and to GPIO (1) input at MCU. Second GPIO (2) connected to your relay main contact. The pushbutton will be read continuously inside MCU. Once the pushbutton is closed GPIO (2) output will switch the relay and finally the load. If something happens to your application, where you need to overturn the pushbutton, you will just open GPIO (2) output, which then opens the relay.

Best regards,

TBencher

[hassna]

Hello TBencher,

Thanks for your feedback.

I would like to check with you if in the both cases, is it needed to add a pull up or down resistor? If so, how to determine its value?

I checked the datasheet but I could find any detail about the following elements:

1- the maximum current that can be provided in a normal GPIO.

2- the voltage of a normal GPIO.

Finally, I need to connect a LED that can function with a range of voltage of 1.8VDC to 3.3VDC  with a nominal value of 2VDC (Q10 series (rs-online.com)). I would like to ask for advice how to do the calculation and choose the right resistor value.

Kind regards.

[TBencher]

Hi hassna,

please find all electrical specifications in https://myicp.infineon.com/sites/microcontrollers-aurix_customer_doc/Lists/defaultdoclib/AURIX%20TC3... .

It is valid also for other TC3XX devices. 

It seems to me that you have not very much experience with the electrical side of your application. Hence, I would like to encourage you doing some study with "Google" or even books to find out how those things work 😉 

Best regards,

TBencher