ESP8266 Community Forum

- Mon Feb 27, 2017 2:12 pm #63099

Phil should it not be 0.63 which is one time constant as opposed to 0.69 ?

So it seems!

Funny how you have something in the back of your mind from years ago and it turns out to be wrong! Let's be nit-picky - 0.63212 !!

I'm not even sure that the method would work, but it's worth a try.

Phil

Haha Sorry mate I am a stickler for detail. I think the method is good but you know what I would do is use a capacitance meter lol

Dans

- Tue Feb 28, 2017 12:17 am #63121 As an interperter there it is not really posible to get timing down much more.

Serial terminal in the chrome browser see https://serialTerminal.com

http://esp8266basic.com
A BASIC interpreter for your ESP

Working now on Autodrop3d. A 3d printer with automatic part ejection system. https://autodrop3d.com

- Tue Feb 28, 2017 7:49 am #63132 it can be done with only one gpio, too:

Connect cap between gnd and gpio,
switch gpio to output and low,
wait for some time,
set gpio to input with pullup,
check time until gpio signals high.

it is coarse but for some aplications it is good enough ...
(definitely not for pF)

- Thu Mar 02, 2017 6:39 am #63225

it can be done with only one gpio, too:

Connect cap between gnd and gpio,
switch gpio to output and low,
wait for some time,
set gpio to input with pullup,
check time until gpio signals high.

it is coarse but for some aplications it is good enough ...
(definitely not for pF)

Absolutely; that is exactly what the PicbasicPro compiler does.

Thanks for the insight, guys. I realize an interpreted platform can no way handle that timing. I guess snicking a 555 would yield timings in a similar range, so thats out.

Best way seems to be to use a pic just to measure the capacitance (a home made sensor for measuring the amount of water, incidentally), and the read it off the ESP via the UART.

Thanks again, guys.