Oak using with Grove sensor

[Graham]

I started to power directly using the VIN and GND. It still stays low when triggered. See particle snip below. I wet my fingers, place over the terminals, trigger event, then dry and still it stays low for a lonnnnng time. Not sure what I am doing wrong.

[exeng]

Did some experimentation using your code but replacing the particle output with serial output (FTDI board) so I could see what the code was seeing (HIGH or LOW). With a 560K pull up resistor I could see it go low and stay low for about 2 of your five second loops then back to high. I tried a 100K but with that value pull up I could not get it to go low because of the high resistance through water. You can think of the pull up and the water as basically creating a voltage divider with the input as the middle tap. So with the 100K pull up and the high water resistance the pull up is keeping the input high. I then tried a 180K pull up and it seem to work well as there was only one cycle of the low state when I removed the probes from the water.

I'm guessing that there may be some capacitance at play here in combination with the 560K being too high a resistance for it to recover (go high) quickly. Too low a value and the water resistance is too high for it to bring the input low.

Try some values lower that 560K but higher than 100K for the pull up. 180K work for me by your mileage may vary as they say. All of this was done with the pull up connected to VCC (3.3V).

[Graham]

Hi Exeng. Many thanks. I also tried with a 180k and it seems to work quite well. Will let you  know of any other changes. Thanks for your help. Graham