A thermistor sensor, 10k ohm.
Great write-up by DVDoug!I would add one thing: Ways of driving the Power Resistor(s) or NiChrome wire [hereafter referred to as the Heater or Heating Element], since in most cases an Arduino output will NOT be able to source or sink the required current AND/OR if the voltage supplied to the Heating Element is greater than +5.OK, one other thing: How about using a thermistor to implement a control loop. Use the Arduino to turn on the heating element until, via the thermistor, a target temperature is reached. In which case, turn the heating element off. And, as DVDoug suggested, have two "set points", one slightly higher than the other such that, the heater is left on until the temperature reaches the first set point, then turn it off until the temperature falls to the second set point. The difference between the two temperature set points, is called the "deadband" and causes a hysteresis effect. The smaller the deadband, the more often the heating element will cycle.In the attached schematic, a MOSFET drives the Heater, and the Thermistor is the upper part of a voltage divider, and the voltage at H3 varies with temperature. Since you didn't divulge the target temperature (in the box), you will need to select an appropriate thermistor, OR if it's a temperature so high that no thermistor will suffice, then consider a thermocouple or other means of determining the temperature.The values and Jameco part numbers are merely suggestions. Choose a "Logic Level" MOSFET that can easily handle the current required to drive the heater. The suggested RFP12N10L is a 100V device that can handle up to 12Amps (though, a heat sink may be required at currents that high). I selected it because it's low cost (only 79 cents), yet has some beef to it. R1 is to limit current in cases where the MOSFET's input capacitance is high enough to cause an inrush current that might damage the Arduino output. 1/4 Watt is fine.
What is the operating temperature range for the heater ?
Uhmm, no. If at full load it's 50W it's 25W @ 50% duty.Instantaneous power is given by:P(t) = U(t) x I(t)Average power is:For a 50% duty cycle that's the same as T = 1, Ton = 0,5 and Toff = 0,5. Filling that in gives:And that's why we use RMS (although mostly for sinusoidal AC). So you could still use:Pavg = URMS x IRMSFor the above PWM for example with 5V and 10A:And 3,54V x 7,07A = 25W again
Is that an INDUCTION heater designed to heat ferrous objects like steel bars or bearings by magnetic eddy currents? If so, it won't heat air. Induction Heater
between 36 and 38 degrees
When you consider that a DC motor's power output is normally controlled via PWM there is absolutely no difference in replacing the motor with a power resistor.