Anyone got any views on making a capacitor meter using the photon? I need to measure small capacitances. I like the third style on this page that just uses the Cap connected to the microprocessor http://www.circuitbasics.com/how-to-make-an-arduino-capacitance-meter/ I would just output to the con…

[image] rocksetta: Putting 100 variable resistors in series seems an expensive approach. Why would you need 100 variable resistors? Given the wide range of timings that are useful, I would think that 8 to 16 fixed resistors would be enough to give you good readings over a wide range of capaci…

If you used PWM, then wouldn’t you also need to add a series diode, otherwise when the 1010101010, etc, bit stream was zero it would discharge the capacitor wouldn’t it? Multiple charging resistors, something like 100K, 1M, 10M on three different digital pins sounds like it’s worth trying. Do you n…

[image] timx: If you used PWM, then wouldn't you also need to add a series diode, otherwise when the 1010101010, etc, bit stream was zero it would discharge the capacitor wouldn't it? Since your not switching from output to input I don't think that will discharge the cap but if it does I will…

Good news. Adding Particle.process(); in my charging while loop solved the dead photon solid green LED issue (Thanks for the idea @timx ) Bad news:PWM for charging capacitors is out of the question. Not because it discharges the cap, but because it does not seem to be a linear relationship. I sta…

Have you considered something like this Digital potentiometer A digital potentiometer (also called a resistive digital-to-analog converter, or informally a digipot) is a digitally-controlled electronic component that mimics the analog functions of a potentiometer. It is often used for t…

That looks much better than what I was able to find. Thanks @ScruffR . I think I will order a few of those. Great price. ($1.50) ... So I ordered a few of those today, but while I am waiting for the shipment I am still confused how to make @timx digital pin controlled 3 resistors. [image] timx…

I hope you haven’t damaged anything with that circuit. When D0 is HIGH and D2 is LOW, for instance, you are essentially bypassing your 10k ohm resistor (its in parallel with a wire, a zero ohm resistor), effectively connecting your LED directly to ground (D2 in the output low state) with no current …

Wow. thanks @Ric for spending the time on the explanation and great circuit diagrams. I was a little lost on the circuit. Can someone explain why I don’t need to use INPUT_PULLDOWN or INPUT_PULLUP and I also did not need to do digitalRead(D2);. Just setting the pins to INPUT seems to be enough. The …

[image] rocksetta: Can someone explain why I don't need to use INPUT_PULLDOWN or INPUT_PULLUP and I also did not need to do digitalRead(D2) The purpose of setting the pins to INPUT is to effectively disconnect the resistors that are connected to those pins. In input mode, the pin has a high i…

So with some minor changes my capacitance meter code is working fine. I just have to wait until I get back to school to test it with some really small capacitors using some really larger resistors. Nice part with this code is that I can set calibration constants for each of the 3 resistors to get th…

Capacitance meter using the Photon

General

rocksetta May 31, 2017, 2:23am 33

That is a nice seqway into my next topic, the Photon test PCB. Has anyone made one?

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Capacitance meter using the Photon

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