通过Android ADK从热敏电阻读取热敏电阻无效的Celsius
题
我在Mario Boehmer的书中的项目8,开始Android Adk与Arduino。 我正在使用10k热敏电阻,具有以下值,但我的温度报告为6531.0c,这显然是不正确的。
long r0 = 10000;
long beta = 4050;
// temperature in kelvin at at 25 celsius
double t0 = 298.15;
// value of second resistor
long additional_resistor = 10000;
// input voltage
float v_in = 5.0;
.
串行监视器的读数如下:
currentThermistorResistance: 128378.38
currentTemperatureInDegrees: -22.16
convertedValue: -221
voltageMeasured: 0.36
.
完整代码如下:
#include <Max3421e.h>
#include <Usb.h>
#include <AndroidAccessory.h>
#define COMMAND_TEMPERATURE 0x4
#define INPUT_PIN_0 0x0
// Size: 5mm
// Resistance: 10KΩ
// Temperature: -30°C to +125°C
// Tolerance: ±10%
//-----
//change those values according to your thermistor's datasheet
// original
// long r0 = 4700;
// long beta = 3980;
//new
long r0 = 10000;
long beta = 4050;
//-----
// temperature in kelvin at at 25 celsius
double t0 = 298.15;
// value of second resistor
long additional_resistor = 10000;
// input voltage
float v_in = 5.0;
double r_inf;
double currentThermistorResistance;
/*
AndroidAccessory(const char *manufacturer,
const char *model,
const char *description,
const char *version,
const char *uri,
const char *serial);
*/
AndroidAccessory acc("UW MHCID",
"HCID TempSense",
"A temperature sensing android application",
"0.1",
"https://github.com/pdugan20/hcid-temp-sense",
"0000000012345678");
byte sntmsg[6];
void setup() {
Serial.begin(19200);
acc.powerOn();
// changed from powerOn() to begin()
// acc.begin();
sntmsg[0] = COMMAND_TEMPERATURE;
sntmsg[1] = INPUT_PIN_0;
r_inf = r0 * (exp((-beta) / t0));
}
void loop() {
if (acc.isConnected()) {
int currentADCValue = analogRead(INPUT_PIN_0);
float voltageMeasured = getCurrentVoltage(currentADCValue);
double currentThermistorResistance = getCurrentThermistorResistance(voltageMeasured);
double currentTemperatureInDegrees = getCurrentTemperatureInDegrees(currentThermistorResistance);
// multiply the float value by 10 to retain one value behind the decimal point before converting
// to an integer for better value transmission
int convertedValue = currentTemperatureInDegrees * 10;
sntmsg[2] = (byte) (convertedValue >> 24);
sntmsg[3] = (byte) (convertedValue >> 16);
sntmsg[4] = (byte) (convertedValue >> 8);
sntmsg[5] = (byte) convertedValue;
acc.write(sntmsg, 6);
delay(100);
}
}
// "reverse ADC calculation"
float getCurrentVoltage(int currentADCValue) {
return v_in * currentADCValue / 1024;
}
// rearranged voltage divider formula for thermistor resistance calculation
double getCurrentThermistorResistance(float voltageMeasured) {
return ((v_in * additional_resistor) - (voltageMeasured * additional_resistor)) / voltageMeasured;
}
//Steinhart-Hart B equation for temperature calculation
double getCurrentTemperatureInDegrees(double currentThermistorResistance) {
return (beta / log(currentThermistorResistance / r_inf)) - 273.15;
}
.
有没有人有任何想法? 我的完整代码在这里: https://github.com/pdugan20/hcid-temp-sense
所讨论的热敏电阻是以下数据表的103: https://drive.google.com/file/d/0bwon70droimfz0frz2vssvhkq00/edit?USP= Sharing
解决方案
很愚蠢...... 我使用1k电阻而不是10k电阻。 替换硬件,现在正好工作。 谢谢大家帮助。
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