Arduino Interface -5v to 5v

Using Arduino Microcontrollers
1

Hello Everyone,

I have a question related to Arduino, I would like to read -5v to 5v input using Arduino ? How can I do that and which board you recommend for this? Please let me know your view about it, Thank you

2

One method: use a voltagedivider to reduce the signal to +/-2.5V, run it thru a capacitor, connect that to the junction of two 100K resistors connected to +5 and Gnd, so the signal is sitting at an offset of 2.5V, and read that with a 5V powered Ardiuno.

Capacitor value, 1uF, 10uF, 100uF, really depends on what frequency of AC you want to let thru.

Plus Minus 5V to 2.5V.jpg
Plus Minus 5V to 2.5V.jpg960×720 25.1 KB

3

Just two 10K resistors. One as pull-up from the analog input to +5V. The other in series from analog input to your -5V to +5V signal. Grounds need to be connected.

4

Thanks for the reply CrossRoads and dlloyd,

This is my first time in the forum. I hope you can be bit patience about my novice knowledge on electronics ;).

  1. I have a distance sensor which can measure 80mm to 300 mm.
  2. I check the voltage across the sensor at 80mm to 300 mm -22.34v to 22.34v.
  3. So, I scaled down the voltage -5v to 5v to compatible with Arduino Uno.
  4. Actually I want it to vary between (0v - 5v), (80 - 300mm).
    I don't want it to be a negative voltage which may possibly damage the board. How can do that?

So, Please guys let me know your view about it. Thank you :slight_smile:

5

Welcome to the forum.

The suggestion I made should work. The series 10K resistor not only completes a voltage divider, it will protect the input from overvoltage. The sensor's output could vary from -10V to +15V without harming the Arduino's input.

Do you have a link to the sensor?

6

Thanks for reply dlloyd,

Please see the attached datasheet about Laser distance sensor. Let me know what you think about it.

193924_eng-Datasheet.pdf (347 KB)

7

Here is the manual.

The analog output is 4-20mA. Normally a 250Ω resistor is used to get 1 to 5V measured across the resistor, but at this point, I'm not sure how this would connect to an Arduino because I don't know if analog- can be connected to Arduino GND.

What resistor did you use to get -5V to +5V? Where did you measure this from?

I guess if you just connect the grounds together, and you use something around 620Ω across analog+ and analog- you would get about 10V swing (-5V to +5V) ... but the max resistance allowed in the specifications is <=500Ω.

I suggest contacting a technical representative to find out how to properly interface the analog output of this sensor to a 5V micro-controller.