REXYGEN Community Forum

mikeyh

Member

From: New Zealand

Registered: 2016-04-28

Posts: 44

LIN block with hysteresis

Hi All,

I have been doing a lot of fan speed control with the PIDU block. Using a function of ambient temperture for SP.

I'm looking at making things a little simpler and using a LIN block with a relationship between fan speed and ambient temperature. What I can't seem to work out is how to use the LIN block block with some kind of hysteresis. I need the out put of the LIN block to be stable a not have a fast rate of change. I thought about using the rate limiter block but wondered if there was a another way? Maybe step changes of somewhere between 2-5 degrees with dead bands.

Thanks in advance

Mike

tomáš čechura

Administrator

Registered: 2016-02-22

Posts: 371

Re: LIN block with hysteresis

Hi Mike,

I prepared for you one solution which came to my mind. Please find it attached. It is not that straightforward but it works
Hope it helps.

Regards, Tomas

hysteresis_example.mdl

---

Raspberry Pi as a miniature industrial PC. Analog and digital I/O, RS-485 and 1-Wire bus.

mikeyh

Member

From: New Zealand

Registered: 2016-04-28

Posts: 44

Re: LIN block with hysteresis

Hi Tomas,

Thank you for the example, it works well. I'm still trying to get my head around how it works...!

Cheers

Mike

jaroslav_sobota

Administrator

Registered: 2015-10-27

Posts: 535

Re: LIN block with hysteresis

Hi Mike,
basically it degrades the resolution of the temperature sensor to 2°C (or whatever deadband you define). Smaller variations in temperature are ignored (the SHLD block is not triggered).

You can "decode" the algorithm by following the arrows and studying the documentation of individual REX function blocks.

If you get stuck at some point, post your questions here.

Best regards,
Jaroslav

---

Monarco HAT for Raspberry Pi - Lightweight I/O for monitoring, archiving and control.
Raspberry Pi in industrial automation!