ACS712 Low Current Sensor as Proximity Sensor

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Ray Depew
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Joined: Mon Nov 27, 2017 8:43 am

ACS712 Low Current Sensor as Proximity Sensor

Post by Ray Depew » Mon Nov 27, 2017 9:56 am

I want to use the ACS712 Low Current Sensor as a proximity sensor. When I connect the ACS712 (SEN-08883, not 8882) to the Arduino, I get a lot of drift on the sensor output. Eventually it settles down and I can get 5.0 V with a refrigerator magnet next to the ACS712 and 0.0 V with the magnet far away - but it still drifts occasionally.

By "drift", I mean that the output lazily rises or falls without any action on my part.

Not having done a lot of work with Hall-effect sensors, I need some advice on how to stop the drift. I am running the sensor completely open-loop; pins IP+ and IP- are not connected to anything. Do I perhaps need to put a load resistor between them? And if so, do I need something big, like a 1 Mohm, or something smaller (and how small)? I assume that a bare copper jumper is not a good idea.

The discussions at https://forum.sparkfun.com/viewtopic.ph ... 12#p189911 and https://forum.sparkfun.com/viewtopic.ph ... ct#p117005 may be relevant to my question, but they don't quite give the information I'm seeking.

Regards
Ray

jremington
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Re: ACS712 Low Current Sensor as Proximity Sensor

Post by jremington » Wed Nov 29, 2017 9:38 am

If you are intending to detect iron-containing or other magnetic materials, a better choice might be a magnetometer capable of measuring the Earth's magnetic field (i.e. a digital compass). They don't drift, although temperature changes could have an effect.

Automobiles can be detected from several meters distance, as a result of the disturbance in the local magnetic field.

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