According to Pete - Current Sensing


In today’s episode of “According to Pete” - the zany (yet informative) video segment starring our Director of Engineering Pete Dokter - Pete explores the world of current sensing. In particular, Pete explains how to use the ACS712 low current sensor breakout.

As always, feel free to leave your comments, questions or suggestions in the comments section below! We hope you enjoyed this month’s edition of “According to Pete.”


Comments 25 comments

  • Whatever happened to the Spectra Symbol contest? Who won?

    • The three top comments/ideas got swag, and we’re discussing the various ideas with SpectraSymbol. The easiest and most likely idea to go to production is the LED matrix, but we’re also looking at the book idea. It seems that the book might not be as expensive as we thought…

  • Hello Dir Support Team

    I have the 5A version of ACS712, and i would like to measure 50mA from a LED stripe, using Energymicro STK 3700. after making all connection the GND Pin and the VCC pin of the ACS712 are signaling a contact that mean something is wrong with my circuit. As I am a begginner,could someone please tell me how i could design my circuit to avoid this problem ? First I used a 12V power supply for the LED, and a 5V power supply for the ACS712 separately, but the output voltage was stilled 0V. Then when i connect my circuit so that the GND of 12V supplier and the GND of the 5V are connected it work but after a few days the ACS712 sensor signals a contact between his GND PIN and his VCC PIN and becomes heater that means something is wrong. could someone please have an circuit example how it could work with a 12V LED and the 5V power supply.

    Thanks in advance !!!

  • R3 & R4 trimpots values please :) And thanks for the video!

  • Schweet, I am familiar with the ACS712, I have used both the 5A and 20A family in design. I like how the thru-current pins are on one side; it makes it easy to nudge those up against the inlet of the board, relatively out of the way. Pass-throughs are even easier.

  • Gotta ask where you got the shirt.

  • It’s all great until someone opens the door next to the white board and hits poor Pete in the back of the head.

  • You know, I’m pretty good with electronics… but you lost me about half way through.

  • “Make love to the camera!”

    Best part of the video.

  • I use the INA219B in this https://www.tindie.com/products/FriedCircuits/usb-tester-oled-backpack-with-display/ . It works really well over i2c.

    Thanks for the how to on the ACS712. I tired and it didn’t go so well for AC. So then I tried the ADE7753 and didn’t go well either.

    http://www.mobilewill.us/2013/01/smart-outlet-ade7753.html

    Haven’t found a great way to monitor 110AC.

    • AC is the easiest to measure since it produces an oscillating magnetic field around the wire that can be picked up by a coil. The voltage on the coil is proportional to the ac current. Checkout Sensors > Current for some ac current sensors. You don’t even have to cut the wire!

  • Aha, I’ve owned a few of these and always ended up averaging the readings as I found them noisy, and didn’t know to expect it…makes me wonder, what is the noise from? Thermal noise with the high gain op amp?

    Thank you, Pete (also)

    • Could be from many sources, not the least of which are the pots on that board. Makes me want to put down a couple of through-hole option components to set the gain on it… but the offset still needs to be variable, I think.

  • Have you ever used any of the HCNR20X High linearity Opto Couplers and/or do you have any thoughts pro/con on them. http://pdf1.alldatasheet.com/datasheet-pdf/view/64618/HP/HCNR200/+4_529UEMZhDOTB-A+/datasheet.pdf

    Basically they are a matched packaged pair LED and Photo Diode. You will get a 1.6V LED voltage drop on the sense side, and you are limited to about 25ma of current. But it’s pretty accurate for small current sensing applications. They have about a 15% transfer gain so 10mA through the LED = 1.5mA through the photo diode. Then it’s just a matter of connecting the Photodiode to an opamp in some configuration to convert the 1.5mA sense current to a usable voltage.

    I had trouble using the ACS712 with an application that had voltages < 5V and very small currents.

  • Pete did you write on the whiteboard 1.2m Ohms as 1.2mA? (see 4:16 in the video)


This Week

This Month

Heartbleed

Happy Arduino Day!

SXSW Create 2014