Level Sensors

Hi List, this is my fist approach to the electronic word I would like to connect the arduino with a Level Sensor here the data: Rated Power (max.) 100 W Switching Voltage 400 V Switching Current (max.) 1.0 A Carry Current (max.) 2.5 A Contact Resistance (max.) 150 mOhm @ 0.5V & 10mA

I now that i should calculate the Ohm Law but im completly lost:

1) mOhm means micro ohms or mega ohms? 2) Arduino shoud have 5V and this is the only part of equation clear

but to calculate the resistor where i find the amount of ampere used by the device ?

That data is totally strange for a level sensor. Any link to its datasheet?

Yes

https://standexelectronics.com/resources/technical-library/technical-papers/datasheet-ls03-series-liquid-level-sensor/

http://www.gotronic.fr/art-detecteur-de-niveau-no-mls31a-11545.htm

It’s a level switch / float switch, no need to calculate anything.

If it’s got two wires then connect one to an Arduino digital pin, the other to a ground pin (GND). Use this in setup()…pinMode(mySwitchPin, INPUT_PULLUP);
and read the switch with mySwitchState = digitalRead(mySwitchPin);

Note: try and keep the water out of the Arduino when playing with float switches :slight_smile:

Ok thanks for the answer, but your answer then generate immediatly another: When I've to use the resistor ? into the aurdunio start kit book it's used a restistor even with a swith (push botton ) on/off I also find this article about level sensor and it also consider the use of resitor

http://www.gammon.com.au/switches

If you use INPUT_PULLUP, as suggested by Martin-X, there is generally no need for a resistor.

This similar example may help: https://www.arduino.cc/en/Tutorial/InputPullupSerial

Thanks to all for your helps

Sorry I didn't give an explanation. To add a bit more to @Archibald's reply, have a look at these:

https://learn.sparkfun.com/tutorials/switch-basics

http://playground.arduino.cc/CommonTopics/PullUpDownResistor

and if you want to calculate the resistor value for yourself... https://learn.sparkfun.com/tutorials/pull-up-resistors

and to answer the first part of your question, a lower case m prefix means milli (one thousandth). https://en.wikipedia.org/wiki/Metric_prefix