Connection of LEM LA 25np

Other Hardware Sensors
1

I need help to in the connection of Current Transducer LEM LA 25np.

  1. How to wire the 10 pins of the LEM LA 25-NP, do I use only one pair (like Pin 1 and Pin 6)? Can I leave the others unconnected?

  2. Should I use breadboard, or PCB layout?

2

See LA25 NP datasheet:

3

Why did you choose a current transducer that can't be easily interfaced with an Arduino.
For starters it needs a bipolar 15volt supply.
The many pins seem for input current range selection.
If you're going to measure mains currents then don't use a breadboard.
Leo..

5

Thank you for your reply!

I'm still learning, so I would really appreciate your guidance.

I'm using the LEM LA 25-NP just to measure DC current after a rectifier in a small wind turbine project. I'm not working with mains AC.

Right now I have:

  • The sensor,
  • A ±15 V power supply,
  • An Arduino to read the output.

I'm only planning to use Pin 1 and Pin 6 for the current to pass through the sensor.

  1. Is this correct?
  2. How should I connect the sensor output (M pin) to the Arduino analog input?
  3. Do I really need a PCB, or can I test it on a breadboard if the current is small?

Thanks again! I really appreciate any help or advice.

6

Thanks! I’ve checked the datasheet, and I understand the sensor needs ±15 V power and gives a current output from the M pin.

Just to make sure I’m doing it right:

  • I plan to pass current from my rectifier through Pin 1 to Pin 6 (only one pair).
  • I connected a 150 Ω resistor from M to GND and read the voltage across it with Arduino.
  • Is that correct?
  • Can I leave the other 8 pins unconnected?
  • Should I avoid using a breadboard if I’m only testing low current?

Appreciate any advice to avoid mistakes. :folded_hands:

7

What about the negative voltage it could produce, which will destroy the Arduino pin.
Are you OK with the small resolution (current steps) you're getting with this combo.

What voltage and current can be expected ftom this wind turbine.
A digital sensor, like the INA260 could be much better suited.
Leo..

8

Thank you so much for your feedback.

I haven’t fully wired the sensor yet. I now realize that if the Arduino GND isn’t properly tied to the virtual ground between the +15 V and −15 V supply, the output from the M pin could swing negative relative to Arduino which could damage the analog pin.

I’m still working out how to make sure the burden resistor is correctly referenced and protected. I was planning to use something like 150 Ω from M to GND and measure the voltage across it, but I’ll double-check the grounding.
The turbine is expected to produce 500W.

I’ll also look into your suggestion of the INA260, seems more Arduino-friendly for longer-term use.

Thanks again.

9

I asked for the voltage/current limits.
The INA260 limits are 36volt/15Amp.
Leo..

10

looking at a past projects I used the ACS712 Current Sensor IC to read the supply current to a Hydraulic RAM
the RAM was compressing a material and when the input current reached a set point the RAM was withdrawn

these days I would probably use a current sensor with an I2C interface for easy interfacing
try a web search for I2C current sensor
e.g. Adafruit INA260 High or Low Side Voltage, Current, Power Sensor

11

High or Low-side is contradictory if you read the datasheet.
The common mode range suggests it's best used high-side, unless used uni-directional.
Leo..

12

That will not work!
What is the maximum current you want to measure.

I connected a 150 Ω resistor from M to GND and read the voltage across it with Arduino.

May or may not work depending on the max current.

13

Is this a 12V, 24V or 48V turbine.
Leo..