The specific realization of temperature control: a

After a quick one-month pre-commissioning process, the project finally starts to start debugging the temperature control process.

One: PWM temperature-controlled waveform-pt100 the waveform.

The project uses PWM to achieve the temperature control, first only using the proportional factor to achieve this process, that is (set temperature value-the actual temperature value) is the feedback amount, according to the control ratio coefficient of the amount to achieve the controlled temperature.

Some important parts of the program are:

In order to achieve temperature control and finally achieve stability, then the final input in the nMOS tube gate signal must be a constant duty ratio of a PWM wave, like the same.

And finally through the Pt100 through the AD620 amplified voltage waveform image is as follows:

Analysis of the above-mentioned image shows that the output PWM voltage maximum value is 728MV,PWM minimum voltage of 492mV, the duty ratio of 5.48ms/47.82ms=0.1146

So the effective voltage is: 546.118mV corresponding temperature value is: 77.7 ℃

Average voltage: 519.0456mV The corresponding temperature value is: 73.8 ℃

Using the infrared thermometer to measure about 73.2 ℃, considering the various aspects of the error, we can roughly verify that we should use the average voltage collected by Pt100 as the actual temperature corresponding to the voltage value. (In fact, this should not be difficult to understand, this is an indicative voltage, not the heating voltage, so the effective value (power) to indicate the less reasonable)

Two: The PWM duty-to-temperature value of the corresponding relationship

From a large number of test results, it is known that the duty ratio of each PWM waveform corresponds to a fixed temperature. If the duty ratio of 0.1146 PWM waveform corresponds to 73.8 degrees Celsius, the duty ratio of 1 of the waveform corresponding to the temperature of about

Then it is necessary to make the curve of duty-temperature, which is a necessary part of the tempering.

The specific realization of temperature control: a