Capacitance meter using the Photon

[rocksetta]

@joost

Secondly, if you want to measure small caps - are you talking picos?

I am trying to read the impedance of the capacitors I am 3D Printing mentioned here:

Protopasta Conducting Filament and the Photon

Here is todays’ images The black PLA is electrically conductive 3D Printed filament and the yellow is regular insulating filament. Not touching light off [image] … Touching, light on [image] So lets try 2 capacitors. First a traditional parallel plate. It worked but very low values even with larger resistors on the voltage divider. I maxed out at 100K ohm resistor so maybe it would work if I got into the M ohms. [image] Next a forked capacitive touch sensor design I saw on Thingive…

The cap in question looks like this

so I am not sure if they are uF or pF.

@peekay123

you will need to adapt the values for a 3.3v system and for a 12-bit ADC. The input impedance of the ADC may impact the readings so you will want to a) Add a series resistor to the capacitor to slow the rise time and b) keep that resistor relatively low so the impedance effect is negligible (10K or less).

I was wondering if things would be much different for the Photon than the Arduino, I might be able to tune the output in the software based on a few known input caps, or using @peekay123 resistor suggestion.

Two other possible diagrams might be better for the Photon.

The basic one

The more accurate one

Both are from the previous metioned site

http://www.circuitbasics.com/how-to-make-an-arduino-capacitance-meter/

I really like the simple arrangement, possibly with @peekay123 suggestions of a resistor. Any reason to use the other arraignments?