PL-05N 5mm NPN NO Fotek Proximity Sensor Switch out DC10-30V Normal Open

Other Hardware General Electronics
1

Hi People

Please see image below. I want to use a few proximity sensor switches for a lift /elevator project for my old/heavy German shepherd dog using an arduino UNO. Travel 6 Ft.

2 questions please if you will.

  1. Will this switch connection work?
  2. What value resistor do I need.

The 10.4 Volts DC will be coming from 8 X AA rechargeable batteries.
The lift will raise and lower 440 lbs the 6 ft in 10 seconds.
The switches are:
PL-05N 5mm NPN NO Fotek Proximity Sensor Switch out DC10-30V Normal Open
from ebay. I plan to use them for top and bottom limits and open/close on 2 doors.

Thanks for looking
Rick from Canada

2
  1. Will this switch connection work?

No, it will damage your Arduino.

  1. What value resistor do I need.

You need two resistors in a potential divider configuration.

I would use 10K for the bottom resistor and 15K for the top.

3

Sensor seems to be a 3-wire NPN type (internal switch to ground) with a weak pull up (47k) to it's supply.
If so, you can connect the output directly to a digital input pin.

Or use a 10k resistor (as in your drawing) if you're not sure.
Should work both ways.
Leo..

Edit:
A 10k:15k divider with the sensor's internal 47k pull up won't give a proper HIGH (1.75volt).
Another solution is internal pull up on the input pin, and a diode (1N4148) between pin and sensor.
Cathode to sensor.

4

Thank you both so much for your answers/help.

Just to be sure... This is now what I'm planning using the recommended divider.
I took my electricity courses 45 years and am obviously more than rusty:)

800×581 70.7 KB

Cheers

Rick

5

This is now what I'm planning using the recommended divider.

No, I didn't see the 47K internal pull up in the spec, mainly because you did not post a link to it.
As Wawa correctly put it:-

A 10k:15k divider with the sensor's internal 47k pull up won't give a proper HIGH (1.75volt).

So either follow one of his suggestions or remove the 15K altogether and change the 10K pull down to a 39K pull down.

6

Thanks Mike.
Hope I've got it right this time. :frowning:

Rick

7

Yes looks good.

8

I'm back trying again.
Paul__B messaged me that I should really use Wawa's last recommendation above which is....

"internal pull up on the input pin, and a diode (1N4148) between pin and sensor.
Cathode to sensor."

What would the value of the PullUp be? Did I get it right?
![](http://www.hubka.com/PL-05N switch_4.jpg)

Thanks

9

Internal pull up means activating/using the resistor INSIDE the Arduino chip.

pinMode(pin, INPUT_PULLUP);

If you do that in your code, then no external resistor is needed.
Leo..

10

rhubka:
I'm back trying again.
Paul__B messaged me that I should really use Wawa's last recommendation above which is....

"internal pull up on the input pin, and a diode (1N4148) between pin and sensor.
Cathode to sensor."

What would the value of the PullUp be? Did I get it right?
Sorry I got the image URL wrong

Thanks

11

"pinMode(pin, INPUT_PULLUP);

If you do that in your code, then no external resistor is needed.
Leo.."

OHHHhhhhhhhh I get it.

Remove the pullup in diagram above above use the code:
pinMode(pin, INPUT_PULLUP)

That is Way Cool!!!

Thanks so much