Analog multiplexer or analog to digital converter to add analog inputs to NodeMCU?

Question

I asked a question yesterday about the best analog multiplexer to use to add a few additional analog inputs to a NodeMCU. Someone recommended using an ADS1115 analog to digital converter. I am using this for an automatic garden watering project, where I need to read the values from multiple capacitive soil moisture sensors. Here is a link to the sensors- https://www.aliexpress.com/item/33042209039.html?spm=a2g0o.cart.0.0.52713c006kRBs8&mp=1 My question is, would an analog multiplexer or analog to digital converter be better for this project? Thanks!

score 2 · Accepted Answer · answered Mar 19 '20 at 20:44

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I asked a similar question here: Simple (low-performance) ADC multiplexer design

The final conclusion was that a multiplexer was dead easy to use out of the box. For watering, presumably, your sample rate will be in the minutes rather than milliseconds, so switching, stabilizing, and measuring, can easily happen without worrying about it taking too long.

I used the CD4051 multiplexer, which worked well and cost silly cheap on amazon.

answered Mar 19 '20 at 20:44

Toby Eggitt

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And this works with 3.3v? A lot of them only work with 5v. It looks like a very good one if it works with 3.3v. Thanks! – Randomaker Mar 19 '20 at 20:50
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I'm using it to multiplex 3v3, yes. Pretty sure I powered it with that too. Let me dig out the data sheet. – Toby Eggitt Mar 19 '20 at 21:13
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Yes, see: https://pdf1.alldatasheet.com/datasheet-pdf/view/50865/FAIRCHILD/CD4051.html – Toby Eggitt Mar 19 '20 at 21:16
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I might add I was also using it with NodeMCU, not that that should make any significant difference beyond the existing details. – Toby Eggitt Mar 19 '20 at 21:20
ok, thank you so much, that helps a ton! – Randomaker Mar 19 '20 at 21:28

Analog multiplexer or analog to digital converter to add analog inputs to NodeMCU?

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