How to wire LED's to a limit switch?

[Dominick Ferone]

We are looking to wire LED's to light up when a limit switch is pressed. We were wondering how do we wire and put the program in labview? These are not addressable LED's.

[MrForbes]

We were talking about doing something like that...but not using the computer to do it. Just build a "custom circuit" that gets power from the PDB and routes it through the switch, to the LED.

It's a pretty basic circuit, essentially the same as that which you use to turn on a light in a room.

http://www.judgeelectrical.co.uk/images/electrical-explanations/light-switch-schematic.jpg

[Christopher149]

The only thing I would add to MrForbes' post is, if you are using plain LEDs (and not an LED strip of some kind), you should add a resistor in series with the LED. This should be a decent guide (http://en.wikipedia.org/wiki/LED_circuit). The picture in the above post is intended for an incandescent bulb. If it's an LED strip, it probably already has appropriate resistors built into it.

[Sperkowsky]

What leds are you using.

[Mr V]

It all depends on exactly what you want to do.

If all you want to accomplish is turn on the led(s) the simplest and in my opinion the best way to do it would be as Mr Forbes said. The caveats are to add the appropriate resistor(s) if using individual led(s) and make sure that the switch you are using is rated for the current it will carry. If using the common 3 terminal limit switch you want to connect to the C and NO terminals if you want the led(s) to turn on when the switch is pressed. If you want them to be off when the switch is pressed use the C and NC terminals. You could also set it up to do both by connecting the power source to the C terminal, one color say red to the NC terminal and another color say green to the NO terminal. That way the red would be illuminated when the switched is not pressed and green when it is pressed.


Now if you want to, for example to stop your lift motor when it reaches the and turn on the led then you would want to wire it to the Roborio. For that you would connect the C and NO terminal to a signal and ground DIO terminal. You would then want to connect a Spike to a relay port on the RoboRio and the led(s) to the Spike.

[MrForbes]

As mentioned by others, I neglected the dropping resistor in my response. Yes, I forgot...but the reason I forgot, is that you can buy many "LED"s these days in a nice package that include the dropping resistor, and are easy to mount in a panel or such. We have a couple of these on our robot to indicate things to the operator.

Sorry for the confusion....probably induced by lack of sleep....

[GeeTwo]

You would then want to connect a Spike to a relay port on the RoboRio and the led(s) to the Spike.

If you're out of relay ports or want something smaller than a spike, you can operate custom circuits using something like this 5V relay module (http://www.oddwires.com/5v-dc-dual-power-relay-module/?gclid=Cj0KEQiA6ounBRCq0LKBjKGgysEBEiQAZmpvAyYLBO1 IsZIkjmoav7bjDm2luDaNKVd3EOqHscbdoV8aAvFS8P8HAQ) switched from DIO ports. Modules are also available with single, 4, 8, or 16 relays from a wide variety of vendors.

[Dominick Ferone]

We are using these LED's https://www.sparkfun.com/products/12023
Our idea was to have the limit switch get pressed the the strip lights up. We were thinking of simply hard wiring it since we thought it was easier as it was meant for when totes hit it, not to stop anything moving.