Public Lab Research note

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Riffle dev: 'Closer to Conductivity: Measuring 555 Oscillations with an Arduino'

by donblair |

What I want to do

As explained in an earlier research note, we're looking to measure the conductivity of water using a 555 timer. The ideal frequency range of our setup is around 1 kHz, and we're going to need to be able to measure oscillations of this frequency with an Arduino -- which might require some tricks. I'm going to build this research note out as I go along, but for now, I'm just collecting a bunch of "Reference" links online that seemed relevant (sorry it's all jumbled, for now) ...


(Source for this fantastic depiction of the 555's internals.)


I think I've got working code now! I'll need to come back and document this more fully, but the wiring is more or less as described in the linked-to-research-note above, and the code is fairly well commented, here:

References or this

RC time:

1 μS/cm is then equivalent to about 0.64 mg of NaCl per kg of water.

two metal screws about a bottle cap away in water seem to have a resistivity of ~ 160 kOhms

"151" cap is 0.015 uF

water-quality riffle open-water 555


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