Hatch's PID; a couple questions from a new user.

[pastera]

Doing the autotune from cold doesn't give the best settings (even for an autotune) - the phase change can throw off the tuning.
Best way is to heat up to full liquidus then allow to cool to where you see some solidification. At that point switch the unit back on and start the tune.

I have hand tuned my parameters to minimize overshoot but still achieve a decently fast time to stable temperature. Tune by hand does take some patience.

[Dimner]

Have only used 3 other brands of PID and ASSUME autotune on this brand would be very similar. In order for the PV to match up with the SV the unit has to go through 3 or 4 cycles. It'll overshoot the high and power to the pot will go off for awhile until the pot cools down below SV. Then power will again be applied till you get up near the SV and it'll shut off going back down. 3 or 4 cycles of this and the PID will determine the settings of P, I, and D which determine the actual length of time the PID needs to apply power to the pot in order to keep PV close as possible to set value.

When I've set mine somewhere around a PV of 20-30° below SV just press the AT button, let it go through the cycles until the AT lamp goes out. Then you're good for that paticular setup. You could record those P, I & D figures for future use if you run different loads and merely reinsert them for the one without going thru the AT process again. Those heating cooling cycles can take several minutes. The blinking rates of the AT lamp, BTW, don't mean much to us casters. You want it to come on of course, but have to wait until the lamps is out before you are autotuned and those up/down cycles have been all completed.

What is an SV? Do you mean SP? (Set Point)
I understand that PV is the process variable (ie the current temp of the alloy as measured by the thermocouple)

[Mike W1]

Same thing usually marked sv

[HATCH]

Set value
Set point
Same thing


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[38SuperAuto]

Built a temp controller for a Lee 4 20 pot, based on an Auber SYL1512. One question for PID veterans is:

Do you initiate auto tuning with 3/4 full pot, full pot, or other.

I don't typically cast below 50% full pot, so based on reading here, my initial thoughts are to bring lead up to liquid state 3/4 full, kill the heater, turn pot back on at 450F or so, and start the autotune cycle

thanks,

rob

[HATCH]

I always use a full pot. I insert probe and let cool back to a solid.
Then I start auto tune and let it run for a hr.
You want at least a 1/2 pot of lead


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[Doughty]

To follow up on this thread:

After some guidance from Hatch we were able to determine that one of the 2 thermocouples I bought was defective. Upon determining this, Hatch quickly sent me another thermocouple. Due to some "life" events I was unable to test this thermocouple until now. It works as advertised, which is to say, Good. My thanks to Hatch for the way in which he stood behind his products.

[HATCH]

I try to treat people how I want to be treated.
And as noted above I stand behind my products 100%.

Glad we got everything worked out on your unit.