Sunrom Product Code for Ordering: ACS current sensor operates from 5V and outputs analog voltage proportional to current measured on the sensing terminals. You can simple use a microcontroller ADC to read the values. Provides up to VRMS galvanic isolation. The low-profile, small form factor packages are ideal for reducing PCB area over sense resistor op-amp or bulky current transformer configurations. The low resistance internal conductor allows for sensing up to 5A continuous current. Features 5.

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IE: These terminals must be in series with the circuit the measured current is flowing through. This amplified version of the breakout board has two potentiometers on it: Vref and Gain The Vref potentiometer sets the baseline voltage output.

In other words, it adjusts the voltage seen at Vo when there is no current flowing through the sensor 0 mA. This allows the sensor to output negative current readings as well as positive. Vref potentiometer, highlighted The gain potentiometer sets the sensitivity of the device. For example, if the gain is set high, then a smaller current will cause the voltage output to increase more, giving you higher sensitivity and allowing you to sense smaller currents.

Gain potentiometer, highlighted However there are a couple caveats: With higher gain you will see more noise spikes on the output, so smaller currents will be harder to measure accurately. If you are trying to measure larger currents with a high gain setting, your output will saturate or clip and reach the maximum 5V or 0V.

With that in mind, to get meaningful data from the current sensor, you must configure the Vref and gain potentiometers properly. It will help you set the potentiometers and perform calculations to convert raw ADC readings into the actual current in mA.

To properly calibrate the ACS breakout board, you should first consider what type and range of currents you will want to measure. Choosing the Range If you are going to be dealing mainly with DC, positive currents, you can adjust Vref to the lower end of its range.

If you are trying to measure AC currents, you will want to keep Vref about in the middle at 2. This lets your output swing equally in the positive and negative directions. The gain setting will depend on the range of currents you want to measure. Setting Vref To get started, copy and upload the sketch below to your Arduino. You can also find the latest files in the GitHub repository. This allows the sensor to output positive and negative currents! In later steps you will learn how to get actual current readings with this sketch.

To set up Vref, the sensor should have no current flowing through it! If you have one available, it may be useful to also read the output voltage using a multimeter. See the Fritzing diagram below for more information: Having a hard time seeing the circuit? Click on the wiring diagram for a closer look.

This will show the voltage reading from the Arduino in real time. The units are in millivolts. Turn the Vref potentiometer clockwise to increase Vref and counter-clockwise to decrease.

Make small adjustments, as the adjustment is very sensitive! This is because the Hall effect sensor inside is picking up the magnetic fields from the screwdriver. You may want to use a plastic screwdriver to eliminate this effect.

I made one out of an old guitar pick with some scissors! In the Serial Plotter, you should see something like this: Using the RedBoard and Arduino, you can plot the output voltage as you adjust Vref Tune Vref to about where you want it, for example mV. Setting Gain and Sensitivity To set the gain, you need to pass a known current through the sensor and tune the gain pot to achieve the sensitivity your application needs. To do this, you can pass mA through the sensor, and adjust the gain pot until the output voltage is mV above your set Vref.

Make sure your current limit is set to something reasonable NOT above 5A , and turn the power on. Adjust the output to a constant mA current for use in adjusting the gain. But, wait! By placing equal resistors in parallel , you can increase the maximum allowable power dissipation; each resistor just adds their power rating.

Keep in mind that the equivalent resistance will be lower though. You may want to use your multimeter to make sure the current flowing through the circuit is indeed 50mA. The tolerances of resistors can alter this current.

To measure current with your multimeter, make sure to connect it in series! To see a diagram of how to build the circuit for setting the gain, see the Fritzing diagram below: Having a hard time seeing the circuit? With a known, constant current flowing through the sensor, the gain can be adjusted.

The same sketch can be used as last time. Open up the Serial Plotter again. To set the gain, disconnect one of the wires to break the current sensing circuit, when you reconnect it, see how much the output voltage increases.

Subtract this from your Vref, to keep the voltage change also known as delta. An example is shown below: Adjust the change Vdelta to what you need it to be by tuning the gain potentiometer. As mentioned above, this affects the noise spikiness you see in the output: As the gain increases, the spiky noise gets bigger and the Vref changes slightly Note: Adjusting the gain pot also changes the Vref setting slightly, you need to take this into account when you do your calculations.

You should measure your final Vref and sensitivity with a multimeter after calibration. Once you have Vref and the sensitivity settings selected, you can modify the code in the example sketch to print out your current readings in milliamps! Follow step 3 in the code comments to learn how to do this.

Make sure to change the sensitivity and Vref variables to what you have set so the code can calculate the current properly. For more information about the ACS, check out the links below:.


ACS712 Datasheet – Current Sensor – Allegro

Allegro patented a Chopper Stabiliza- tion technique that nearly eliminates Hall IC output drift induced by temperature or package stress effects. This offset reduction technique is based on a signal modulation-demodulation process. Modulation is used to separate the undesired dc offset signal from the magnetically induced signal in the frequency domain. Then, using a low-pass filter, the modulated dc offset is suppressed while the magnetically induced signal passes through the filter. As a result of this chopper stabilization approach, the output voltage from the Hall IC is desensitized to the effects of tempera- ture and mechanical stress. This technique produces devices that have an extremely stable Electrical Offset Voltage, are immune to thermal stress, and have precise recoverability after temperature cycling. This technique is made possible through the use of a BiCMOS process that allows the use of low-offset and low-noise amplifiers in combination with high-density logic integration and sample and hold circuits.


ACS712 Low Current Sensor Hookup Guide

The device package allows for easy implementation by the customer. Typical applications include motor control, load detection and management, switched-mode power supplies, and overcurrent fault protection. The device is not intended for automotive applications. For the automotive grade version, see ACS The device consists of a precise, low-offset, linear Hall sensor circuit with a copper conduction path located near the surface of the die. Applied current flowing through this copper conduction path generates a magnetic field which is sensed by the integrated Hall IC and converted into a proportional voltage. Device accuracy is optimized through the close proximity of the magnetic signal to the Hall transducer.


The device package allows for easy implementation by the customer. Typical applications include motor control, load detection and management, switched-mode power supplies, and overcurrent fault protection. The device is not intended for automotive applications. For the automotive grade version, see ACS


ACS712 Current Sensor User Manual


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