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Strange Case of Adafruit ADS1115 and QIFEI ADS1115
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Please be positive and constructive with your questions and comments.

Strange Case of Adafruit ADS1115 and QIFEI ADS1115

by kevinjwalters on Sat Feb 06, 2021 2:04 pm

I've been testing ADCs recently, just comparing them with the output of the SAMD21 DAC on a Feather M0 Bluefruit. I was buying some other items from a vendor on eBay (UK) and thought I'd get an ADS1115 board. I hadn't really done any research on this and perhaps the 4 USD equivalent price should have raised an alarm but I wasn't aware of the pricing at the time.

It turns out the QIFEI ADS1115 board is probably using a clone of the 12-bit ADS1015 but also displays some undesirable characteristics: the top 4 bits are missing, it doesn't seem to supply data reliabily (i2c dropped to 75000 baud seemed to improve it slightly) and it may be less reliable when powered at 5V - I tested powered at 3.87V from batteries.

I don't have a real TI ADS1115 like the one on the ADS1115 16-Bit ADC - 4 Channel with Programmable Gain Amplifier for comparison, but the QIFEI's bizarre performance can be clearly seen below:

adc-analaysis-run1-20210205-v5-g1.png
Comparison of ADC on Feather M0 vs fake ADS1115
adc-analaysis-run1-20210205-v5-g1.png (222.1 KiB) Viewed 347 times


For anyone else who gets tempted by one of these, this is what the board looks like so you can avoid it.

qifei-fakeads1115-second-top.JPG
QIFEI fake ADS1115 board top side
qifei-fakeads1115-second-top.JPG (563.91 KiB) Viewed 347 times


qifei-fakeads1115-second-underside.JPG
QIFEI fake ADS1115 board under side
qifei-fakeads1115-second-underside.JPG (501.21 KiB) Viewed 347 times
Last edited by kevinjwalters on Sat Feb 06, 2021 2:14 pm, edited 1 time in total.

kevinjwalters
 
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Re: Strange Case of Adafruit ADS1115 and QIFEI ADS1115

by kevinjwalters on Sat Feb 06, 2021 2:05 pm

And I took a close-up photo of the chip:

qifei-fakeads1115-second-iccloseup.JPG
QIFEI fake ADS1115 - chip close-up
qifei-fakeads1115-second-iccloseup.JPG (334.31 KiB) Viewed 346 times

kevinjwalters
 
Posts: 984
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Re: Strange Case of Adafruit ADS1115 and QIFEI ADS1115

by lbarhai on Wed Apr 28, 2021 1:56 pm

We found the same thing on the QIFEI ADS1115. We ordered from the same seller on Amazon 3 different times, and luckily the first time we ordered, the ADS1115 was not fake so we can easily compare the two boards and we found some interesting and noticeable differences that can help you avoid the fake boards.

IMG_4779.jpeg
Front of ADS1115
IMG_4779.jpeg (140.55 KiB) Viewed 254 times

lbarhai
 
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Re: Strange Case of Adafruit ADS1115 and QIFEI ADS1115

by lbarhai on Wed Apr 28, 2021 1:58 pm

Here is the image of the backside of both boards.
IMG_4781.png
IMG_4781.png (695.39 KiB) Viewed 254 times

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Re: Strange Case of Adafruit ADS1115 and QIFEI ADS1115

by kevinjwalters on Thu Apr 29, 2021 8:18 pm

Good sleuthing!

I ended up buying some Seeedstudio Grove bits and picked up one of their ADS1115 boards. Feels more comfortable having a trusted brand of some sort rather than an anonymous board.

kevinjwalters
 
Posts: 984
Joined: Sun Oct 01, 2017 3:15 pm

Please be positive and constructive with your questions and comments.