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Topic: Floating analog inputs question (Read 183 times) previous topic - next topic

BaconPizza

Hello, is it normal for an analog input to still show very small random values even when using a pull-down resistor to prevent floating? I mostly see 0, but every second or so I'll see a value from 1-3. Thank you :)

BaconPizza

#1
Aug 17, 2017, 06:04 pm Last Edit: Aug 17, 2017, 06:09 pm by BaconPizza
Sorry for making this post, I think this answers my question when it says "near zero volts"


MarkT

Hello, is it normal for an analog input to still show very small random values even when using a pull-down resistor to prevent floating? I mostly see 0, but every second or so I'll see a value from 1-3. Thank you :)
That depends on the value of the pulldown and the amount of noise coupled capacitively to the pin.
Yes I'd expect that for 100k upwards if there's noise around.  If there is a long trace on the pcb
or a long wire on the breadboard connected to the pin then 10k might show some counts too.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

BaconPizza

It's an 8:1 mux, since I'm not using Y4 - Y7 I've just put a 10K resistor from each one to ground. It's running on 5V. I was thinking it was possibly because of the resistors leads being exposed on the breadboard, since I haven't cut them to make them shorter.

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