ACS715 Noob question

Robotics and electronics discussion Electronics
1

Hi forumners!

Can you tell me if the ACS715 has to be connected in series with the supply? I want to monitor the current draw of a DC motor and do some solenoid control with the resulting levels/data. I guess the output needs to be calibrated for accuracy?

Thanks

2

Hello.

Yes, the current sensor needs to be in series (the current you’re measuring needs to go through it). Whether you need to calibrate depends on what kind of accuracy you need, but it’s generally a good thing and pretty easy if you’re using a microcontroller anyway.

- Jan

3

Thanks Jan,

Can you advise the kind of distance from the ACS715 output to processor input is optimal? My motor (and ACS715) could be as far away from the a/d as 50 meters. Possible as-is, or would intermediate amplification be necessary?

Cheers!

4

50m is definitely a lot, and I don’t think amplification is going to be enough. A lot of the answer ultimately depends on what kind of quality you need, but you might need to do the A to D conversion at the sensor and then transmit the value digitally across your wires (even that digital transmission might require some special consideration for that kind of distance). If you already have the wire, you can start by just trying it and seeing how bad the noise and distortion is.

- Jan

5

Understood Jan,

Only a microcontroller at the moment with a lot of ideas!

High quality is not so important as the data will not be used for graphing etc but set point(s) will be acted upon. How about converting the sensor output to 4-20mA at the sensor, then back to voltage close to the A/D?

I think current is better for distance measurement with less noise?

Thanks

6

I do not know what you need performance-wise and what you are familiar with, and I have not personally dealt with this problem, so it’s difficult to give you specific advice. If I had to do it quickly, I would start by seeing what quality I get without any extra parts using some twisted pair cable, and if that wasn’t good enough, I would put a little MCU and some kind of long-cable serial driver on the sensor end. It would cost no more than a few tens of dollars even if I used some commercial carrier boards, it would be extendable to several hundred meters, and I wouldn’t have to worry that much about details of the wiring.

- Jan

7

Thanks Jan,

I think you are right I need to keep it simple. No rush.