Sure, thanks.
Here is a picture of the diagram and of the built circuit.
Below is the sketch.
When the heater is off as selected by the rotary switch, the voltage at the gate of the STP16NF06FP MOSFET is zero: When I setup a temperature the voltage changes from 0.2 to about 2.5V and fluctuates. But it seems to remain on even after reaching the target temperature, except if I turn it of by pressing the rotary switch again. Then it goes back to zero.
/*
* heater-with-display.ino
*
* Copyright 2020 Victor Chew
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// Libraries required:
// - NTC_Thermister (Yurii Salimov) [Source: Arduino Library Manager]
// - PID (Brett Beuuregard) [Source: Arduino Library Manager]
// - ss_oled (Larry Bank) [Source: Arduino Library Manager]
// - TimerOne (Paul Stoffregen et al.) [Source: Arduino Library Manager]
// - ClickEncoder (0xPIT) [Source: https://github.com/0xPIT/encoder/tree/arduino]
#include <ss_oled.h>
#include <TimerOne.h>
#include <ClickEncoder.h>
#include <NTC_Thermistor.h>
#include <SmoothThermistor.h>
#include <PID_v1.h>
#define KP 17.07
#define KI 0.75
#define KD 96.57
#define SMOOTHING_WINDOW 5
#define MOSFET_GATE_PIN 3
#define THERMISTOR_PIN A6
#define KY040_CLK 9
#define KY040_DT 8
#define KY040_SW 2
#define KY040_STEPS_PER_NOTCH 2
bool heaterOn = false, pOnM = false;
double pwmOut, curTemp, setTemp = 0;
NTC_Thermistor* thermistor = new NTC_Thermistor(THERMISTOR_PIN, 99800, 100000, 25, 3950);
SmoothThermistor* sthermistor = new SmoothThermistor(thermistor, SMOOTHING_WINDOW);
PID pid(&curTemp, &pwmOut, &setTemp, KP, KI, KD, P_ON_E, DIRECT);
ClickEncoder encoder(KY040_CLK, KY040_DT, KY040_SW, KY040_STEPS_PER_NOTCH);
SSOLED ssoled;
void refreshDisplay() {
oledFill(&ssoled, 0, 1);
char msg[64];
sprintf(msg, "Hotend: %dc", (int)curTemp);
oledWriteString(&ssoled, 0, 0, 1, msg, FONT_NORMAL, 0, 1);
sprintf(msg, "Target: %dc", (int)setTemp);
oledWriteString(&ssoled, 0, 0, 3, msg, FONT_NORMAL, 0, 1);
oledWriteString(&ssoled, 0, 0, 6, heaterOn ? "Heating..." : "- Heater off -", FONT_NORMAL, heaterOn ? 1 : 0, 1);
}
void encoderISR() {
encoder.service();
}
void setup() {
Serial.begin(115200);
pinMode(MOSFET_GATE_PIN, OUTPUT);
pid.SetMode(AUTOMATIC);
pinMode(LED_BUILTIN, OUTPUT);
digitalWrite(LED_BUILTIN, LOW);
encoder.setAccelerationEnabled(true);
Timer1.initialize(1000);
Timer1.attachInterrupt(encoderISR);
oledInit(&ssoled, OLED_128x64, -1, 0, 0, 1, -1, -1, -1, 400000L);
refreshDisplay();
}
void loop() {
// Get rotary encoder values and update display
int _curTemp = sthermistor->readCelsius();
int _setTemp = setTemp - encoder.getValue()*5; // minus because signal from this rotary switch works in the opposite direction
_setTemp = min(300, max(0, _setTemp));
bool _heaterOn = heaterOn;
if (encoder.getButton() == ClickEncoder::Clicked) {
_heaterOn = !_heaterOn;
if (!_heaterOn) _setTemp = 0;
}
// Update display only if something changes
if (_curTemp != curTemp || _setTemp != setTemp || _heaterOn != heaterOn) {
curTemp = _curTemp;
setTemp = _setTemp;
heaterOn = _heaterOn;
refreshDisplay();
}
// Turn on LED if we are within 1% of target temperature
digitalWrite(LED_BUILTIN, heaterOn ? abs(_curTemp-setTemp)/setTemp <= 0.01 : LOW);
// To speed things up, only switch to proportional-on-measurement when we are near target temperature
// See: http://brettbeauregard.com/blog/2017/06/introducing-proportional-on-measurement/
if (!pOnM && abs(curTemp-setTemp) <= max(curTemp, setTemp)*0.2) {
pOnM = true;
pid.SetTunings(KP, KI, KD, P_ON_M);
Serial.println("P_ON_M activated.");
}
// Prevent thermal overrun in case of PID malfunction
pid.Compute();
if (curTemp < 300) {
analogWrite(MOSFET_GATE_PIN, heaterOn ? pwmOut : 0);
}
else {
analogWrite(MOSFET_GATE_PIN, 0);
Serial.println("Thermal overrun detected!");
}
// Display stats
//Serial.print("pwmOut = "); Serial.print(pwmOut); Serial.print(", ");
//Serial.print("diff = "); Serial.print(setTemp - curTemp); Serial.print(", ");
//Serial.print("curTemp = "); Serial.print(round(curTemp));
//Serial.print(" / "); Serial.println(round(setTemp));
delay(200);
}
