Controlling temperature of reprap extruder hot-end

In fact, you could directly use the thermistor transfert function:

hydraraptor.blogspot.com/2007/10/measuri...rature-easy-way.html

A friend recently bought some Platinium thermistors, which are very linear in the range 0°C-250°C. So, I won't need any scaling for the input :o)

I also found the XR4151, a very simple to use VCO, to convert the thermistor value in pulses. As said, these pulses will be read by the encoder module (set in counter mode).

What frequency range do you suggest to use for encoder good reading? Is 100Hz enough? Better use higher frequency? The frequency will only vary in a 2:1 ratio...

Thanks,

Thanks!

The thermal reaction is pretty slow, so no problem for EMC. I will just have to tune the pid.

I think I will also need to use a slipping average on the temperature reading (ie encoder speed). Is there a way to do that, using standard modules?

Ok.

At which frequency would you use this filter? Does it need a slower thread than the servo thread?

How do you determine the gain for a given frequency and rolling period (~1s)?

I got it.

Thanks.

I made a first prototype, using a NE555 to convert the resistor value in a frequency, and it works fine :o) I still have to calibrate the resistor vs temperature curve, and find the correct PID values.

BTW, does anybody have worked on a fuzzy logic component?

Another question about the pid component...

In the Ziegler & Nichols or Broïda methods, they compute Kp, Ti and Td params.

How do I determine Ki and Kd for the hal pid component, from Ti and Td (integration time and derivative time)?