Thanks.I’d recommend using 10kΩ resistors.
Did you know that if you code properly, no resistor is needed? In the setup() routine, initialize the pin with the INPUT_PULLUP option. Then connect the pin through the switch to ground.
This way, if the switch is open, the pin will return HIGH and if it’s closed, it’s value will be LOW. If you desire the opposite values, it’s easy to invert the value/logic in your program/sketch.
Thanks.Are all the limit switches going to just one input?
If so, only one resistor is needed. But if just one input, then you will not know the switch that caused the limit signal.
As @djsfantasi says, you can use no resistor if the internal pullups are on. Then, connect the switched from the input to GND, not +5V.
You don’t use PULLUP resistors on an Arduino. They are built in.You should use the resistor as a pullup, not a pulldown. The way you have it connected the Arduino pin will not see any current limiting. The resistor is for the Arduino input, to prevent it from floating. And, yes, only one resistor is needed, because it's for the Arduino pin.
You certainly can use external pullup resistors. No law against it. Internal pullups are weak.You don’t use PULLUP resistors on an Arduino. They are built in.
Right, that's why I said it.So you need one resistor for each Arduino pin.
Thanks.You should use the resistor as a pullup, not a pulldown. The way you have it connected the Arduino pin will not see any current limiting. The resistor is for the Arduino input, to prevent it from floating. And, yes, only one resistor is needed, because it's for the Arduino pin.
Thanks.It looks like this, sorry I didn't have a lever micro-switch to illustrate so pretend.
View attachment 209404
When the switch is closed a logic low (0) is applied, when the switch is open a logic high (1) is applied. The choice of using an internal or external pullup resistor rest with the user. On most boards the value of the internal pullup resistor well exceeds the typical external 10K pullup value. On most AVR-based boards, the value is guaranteed to be between 20kΩ and 50kΩ. On the Arduino Due, it is between 50kΩ and 150kΩ. For the exact value, consult the datasheet of the microcontroller on your board. Even then the values you see are approximate.
For what you are doing it really matters not so coding for an internal pullup will do just fine as you likely are well aware by now. In your example drawing in post #1 the resistor is acting as a pulldown and the logic would be reversed from what I have posted here. Just a matter of the logic level based on switch open or closed.
That's my story and I am sticking to it.
You can connect all the switches in parallel if you only need to know when one of the switches closes. If you need to know which one, you will need to connect each switch to a separate pin.Thanks.
What I mean is just use one resistor for all 6 switches, not one resistor for 1 switch, if it's OK? that means hook up 6 switches in parallel to one resistor to GND.
Thanks.You can connect all the switches in parallel if you only need to know when one of the switches closes. If you need to know which one, you will need to connect each switch to a separate pin.
You can use a pull-up resistor or a pull down resistor. Either way, the input will not be floating when the switch is open.
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by Steve Arar
by Luke James