Hello everyone, I am trying to use the input pins of my RPi. I want to connect a button in one of them, and every time it is pressed, a led will be turned on (which will be connected to another pin, which will be configured as an output). I have seen three possible connections:
1: http://pitando.net/wp-content/uploads/2 ... lsador.png
2: The same as in option 1, but with the electronic components exchanged.
3: The same as in option 1, but with a resistance between the circuit and the input pin.
What is the difference between these and which is more advisable?
Thank!
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Sebarahona
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Laurens-wuyts
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Re: Use a button on the input pin.
1: This circuit will work fine, but doesn't have any protection. Here, the input is pulled low when you press the button, so 0 (low) is pressed and 1 (high) is released.
2: This is the same as 1, but instead of being 1 (high) when released, it's 0 (low) and vice versa.
3: The extra resistor is for when you accidentally set the input pin as an output. When the output is 1 (3.3v) and you press the button, there won't be a short to GND cause of this resistor.
Laurens
2: This is the same as 1, but instead of being 1 (high) when released, it's 0 (low) and vice versa.
3: The extra resistor is for when you accidentally set the input pin as an output. When the output is 1 (3.3v) and you press the button, there won't be a short to GND cause of this resistor.
Laurens
Re: Use a button on the input pin.
Hi.
That input circuit will work but its better to have a 1K ohm resistor on the input line to the GPIO like the examples shown here
https://www.raspberrypi.org/learning/ph ... l_up_down/
it gives your GPIO some protection should you accidentally set the GPIO to output with the button pressed.
The LED circuit is ok but I would change the resistor to 470 ohm to reduce the current drawn on the GPIO pin.
That input circuit will work but its better to have a 1K ohm resistor on the input line to the GPIO like the examples shown here
https://www.raspberrypi.org/learning/ph ... l_up_down/
it gives your GPIO some protection should you accidentally set the GPIO to output with the button pressed.
The LED circuit is ok but I would change the resistor to 470 ohm to reduce the current drawn on the GPIO pin.
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Sebarahona
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Re: Use a button on the input pin.
Thanks Laurens! Now I understand the difference between these optionsLaurens-wuyts wrote:1: This circuit will work fine, but doesn't have any protection. Here, the input is pulled low when you press the button, so 0 (low) is pressed and 1 (high) is released.
2: This is the same as 1, but instead of being 1 (high) when released, it's 0 (low) and vice versa.
3: The extra resistor is for when you accidentally set the input pin as an output. When the output is 1 (3.3v) and you press the button, there won't be a short to GND cause of this resistor.
Laurens
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Sebarahona
- Posts: 19
- Joined: Wed Jan 18, 2017 2:36 pm
Re: Use a button on the input pin.
Hi, Thanks for your help, this link has dispelled all my doubts about it!pcmanbob wrote: https://www.raspberrypi.org/learning/ph ... l_up_down/