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Feature: Power limitation #10

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Feature: Power limitation #10

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15 changes: 12 additions & 3 deletions Maiskolben_TFT/Maiskolben_TFT.ino
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Original file line number Diff line number Diff line change
Expand Up @@ -872,10 +872,19 @@ void compute(void) {
last_measured = cur_t;

heaterPID.Compute();
if (error != NO_ERROR || off)

// Power limitation.
// Tips are rated for 40W, do not exceed that.
// note t-hat we have inherently only 50% PWM, as we have it on 10ms and then wait with pwm off for another 10ms.
// Formula: P = 0.5 * ( U^2 / ( R )) * (pwm)
float pwm_max = 2 * PMAX / ((v*v) / 2.4);
if (pwm_max > pid_val) pwm_max = pid_val;

if (error != NO_ERROR || off) {
pwm = 0;
else
pwm = min(255,pid_val*255);
} else {
pwm = min(255, pwm_max * 255);
}
analogWrite(HEATER_PWM, pwm);
}

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2 changes: 2 additions & 0 deletions Maiskolben_TFT/definitions.h
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Expand Up @@ -13,6 +13,8 @@
#define TEMP_STBY 150
#define TEMP_COLD (adc_offset + 15)

#define PMAX (40) // max watts to pump into the tip. (note: Weller specifies the tips as 40W; the big RT-11 has 55W)

#define SHUTOFF_ACTIVE
#define BOOTHEAT_ACTIVE

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