# Current Sensor - ACS723 Problem

**URL:** <https://community.sparkfun.com/t/current-sensor-acs723-problem/38996>\
**Category:** Power\
**Created:** [February 24, 2020, 8:19am UTC](https://community.sparkfun.com/t/current-sensor-acs723-problem/38996 "2020-02-24T08:19:32Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Alice](https://avatars.discourse-cdn.com/v4/letter/a/779978/32.png) [@Alice](https://community.sparkfun.com/u/Alice)\
**Post date:** [February 24, 2020, 8:19am UTC](https://community.sparkfun.com/t/current-sensor-acs723-problem/38996/1 "2020-02-24T08:19:32Z")

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Hello

I am facing a problem with SparkFun Current Sensor ACS723 (Low Current). I am trying to measure the output current (photocurrent) of a photodetector. I calibrated the current sensor to adjust the maximum current that can sense, which is 20 mA using the power supply. However, when connecting it to the photodetector circuit, it does not output accurate values (not even close). Another problem is that even when there is no input to the photodetector, the sensed values of the current sensor are the same.

I am connecting the current sensor with the photodetector as the figure attached. I am using the original current sensor code provided by Sparkfun, but I changed the reference voltage and the sensitivity according to the calibration.

Thank you

 ![PDcircuit.PNG](https://canada1.discourse-cdn.com/sparkfun/original/3X/9/3/93546c154b5654e0f73a45d4bf15858ea8b02e70.png)

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**Author:** ![TS-Brandon](https://avatars.discourse-cdn.com/v4/letter/t/cc9497/32.png) [@TS-Brandon](https://community.sparkfun.com/u/TS-Brandon)\
**Post date:** [February 24, 2020, 5:13pm UTC](https://community.sparkfun.com/t/current-sensor-acs723-problem/38996/2 "2020-02-24T17:13:00Z")

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Hello Alice,

How are you prototyping this circuit? Are you using a Breadboard, or do you have a fabricated PCB? Can you include any camera pictures of your set up?

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<div class="post-metadata">

**Author:** ![Alice](https://avatars.discourse-cdn.com/v4/letter/a/779978/32.png) [@Alice](https://community.sparkfun.com/u/Alice)\
**Post date:** [February 26, 2020, 7:10am UTC](https://community.sparkfun.com/t/current-sensor-acs723-problem/38996/3 "2020-02-26T07:10:46Z")

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I am using a breadboard, please find attached a picture of the setup.

 ![SensorCir.jpeg](https://canada1.discourse-cdn.com/sparkfun/original/3X/8/6/86e3e779543e04a8e08e1f43b3a45e037233153f.jpeg)

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**Author:** ![n1ist](https://avatars.discourse-cdn.com/v4/letter/n/5daacb/32.png) [@n1ist](https://community.sparkfun.com/u/n1ist)\
**Post date:** [February 26, 2020, 5:53pm UTC](https://community.sparkfun.com/t/current-sensor-acs723-problem/38996/4 "2020-02-26T17:53:29Z")

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There are a few differences between your schematic and the picture:

- There is no 5V source for the photodiode circuit in the picture

- There is an electrolytic cap used for the 100nF cap; I would use a ceramic cap instead. Also, it’s hard to see the polarity on the cap.

- The photodiode has three terminals; is it electrically isolated from this pin?

/mike