Connecting SSR to Duet Expansion Breakout Board

tal.raindel

@dc42
Thank you for the answer.

Other problem that I have now is dead time constant, my set have high thermal mass.
The normal tuning give error due to the system doesn't cooling fast enough.
I used M307 to set the dead time to 60 sec but it need to be larger (around 3 min), I have a way to change the max dead time using G code or I need a new build?

version data in the photo.

Great thanks,
Tal

Phaedrux

@tal-raindel said in Connecting SSR to Duet Expansion Breakout Board:

I used M307 to set the dead time to 60 sec but it need to be larger (around 3 min),

So set it to 180?

tal.raindel

@Phaedrux
You can't set it to 180 sec, there is limit in the software (I tried).

dc42

Does your heater show no increase in temperature at all, 60 seconds after turning the heater on from cold?

tal.raindel

@dc42
The heater show temp increase around 60 sec after starting the heating.
When stop heating it take around 3 min until it stop rising and start to have slow drop (All the system have thermal isolation around it).

tal.raindel

I know the heater and the sensor are working from manual test I did.
I powered up the heater manually and I have same temp. rise as i have on my standalone temp sensor i attached.
I'm pretty sure that the problem I have is in the max dead time for the control loop. If there is some thing else worth checking I can do it.

My system have very high thermal mass so it is normal that it will react slow to changes (rise and fall).

tal.raindel

@dc42
Hi,

Do you have any suggestion how to over come the 60 sec limitation for the dead time?

Great thanks for the help!

dc42

@tal-raindel said in Connecting SSR to Duet Expansion Breakout Board:

@dc42
Hi,

Do you have any suggestion how to over come the 60 sec limitation for the dead time?

Great thanks for the help!

Set a higher time constant (C parameter). The dead time can't exceed half the time constant.

tal.raindel

@dc42

Thanks, this allowing me to set the dead time manually to more then 60 sec.
Still the auto-tune is stopping after 60 sec due "temperature is not falling", I can see change in the temperature but after 60 sec it still small fall.
There is way to tweak this parameter also or I need to do manual calibration for each heater?
Please correct me if i wrong in my understanding of the system but if I will set the C parameter to be very high it should be able to do the calibration?

dc42

You will need to set both C and D high, with C at least 2*D.

tal.raindel

I think it is solved.
I did manual calibration for two of the heaters, I assume it will work for the other also.

BTW, what the limits for A and C parameters?