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 consol. From my tablet I cant read the code they used but it should be reasonably easy. Charge the cap then start a timer and read the cap.
My tablet could not read the Arduino code but now I can I just have to change it for the console.
const int OUT_PIN = A2;
const int IN_PIN = A0;
const float IN_STRAY_CAP_TO_GND = 24.48;
const float IN_CAP_TO_GND = IN_STRAY_CAP_TO_GND;
const float R_PULLUP = 34.8;
const int MAX_ADC_VALUE = 1023;
void setup()
{
pinMode(OUT_PIN, OUTPUT);
pinMode(IN_PIN, OUTPUT);
Serial.begin(9600);
}
void loop()
{
pinMode(IN_PIN, INPUT);
digitalWrite(OUT_PIN, HIGH);
int val = analogRead(IN_PIN);
digitalWrite(OUT_PIN, LOW);
if (val < 1000)
{
pinMode(IN_PIN, OUTPUT);
float capacitance = (float)val * IN_CAP_TO_GND / (float)(MAX_ADC_VALUE - val);
Serial.print(F("Capacitance Value = "));
Serial.print(capacitance, 3);
Serial.print(F(" pF ("));
Serial.print(val);
Serial.println(F(") "));
}
else
{
pinMode(IN_PIN, OUTPUT);
delay(1);
pinMode(OUT_PIN, INPUT_PULLUP);
unsigned long u1 = micros();
unsigned long t;
int digVal;
do
{
digVal = digitalRead(OUT_PIN);
unsigned long u2 = micros();
t = u2 > u1 ? u2 - u1 : u1 - u2;
} while ((digVal < 1) && (t < 400000L));
pinMode(OUT_PIN, INPUT);
val = analogRead(OUT_PIN);
digitalWrite(IN_PIN, HIGH);
int dischargeTime = (int)(t / 1000L) * 5;
delay(dischargeTime);
pinMode(OUT_PIN, OUTPUT);
digitalWrite(OUT_PIN, LOW);
digitalWrite(IN_PIN, LOW);
float capacitance = -(float)t / R_PULLUP
/ log(1.0 - (float)val / (float)MAX_ADC_VALUE);
Serial.print(F("Capacitance Value = "));
if (capacitance > 1000.0)
{
Serial.print(capacitance / 1000.0, 2);
Serial.print(F(" uF"));
}
else
{
Serial.print(capacitance, 2);
Serial.print(F(" nF"));
}
Serial.print(F(" ("));
Serial.print(digVal == 1 ? F("Normal") : F("HighVal"));
Serial.print(F(", t= "));
Serial.print(t);
Serial.print(F(" us, ADC= "));
Serial.print(val);
Serial.println(F(")"));
}
while (millis() % 1000 != 0)
;
}
)
