TET-612 PID problems need help asap

[insco2]

If anyone out there in the community is using a TET-612 could you please sound off. This controller comes with such little guidence for the layman, hopefully i could get some assistance from a fellow brewer using this technology.

 

[kladue]

what type of assitance do you need, sensor selection, SSR selection for operating an electric heating element, programming. Have not used the TET-612 but have worked with similar types of PID controllers and can understand the limited instructions for programming that are on the internet.

 

[insco2]

i have the controoler in place and it is controlling my heating through a ssr in the heat exchange unit. the large problem is that when i asked it to autotune it didnt do anything. i went to the store with the at light flashing and came back to a flashing light, when i ask the controller to bring my wort up to a tempurature the device makes the temp and continues to heat the exchanger up past the desired temp. I just figured when it saw it was getting close it would dial the element back, but no it didnt. I guess im going to need to program the thing myself although the direction said to leave that to a proffesional. dont know what else to do. heres a link to all i know about the controller. http://http://www.lightobject.com/support/Manual/TET612_Manual.zip

Thanks for any help ahead of time

 

[kladue]

Try these steps, activate controller and let system come up to temp and begin to cycle heater, then initiate auto tune feature. It might have problems if the autotune duration was less than the time it took to reach setpoint temperature, the auto tune loop would time out. If you try a manual tune procedure let system come to temp and record the time between on cycles of the heater, use this number for the integral time, set proportional band setting to ~40% for start, and derivitive to 25% of integral time.

 

[insco2]

im going to fire this thing up today and run a sample brewe with water at the temps ill be preforming at. I'll turn the at on the whole time and see what happens. do you think it could take more than an hour for the device to autotune?

 

[kladue]

Let the controller bring the water up to temp before starting the auto tune feature, as it looks like the default auto tune time is about 10 minutes. If you start the auto tune before the controller begins to cycle the heater at set point it might not complete the auto tune cycle in time and lockup in the on state. If the tune cycle is still too short then increase the time amount in the Atdu variable to 20 minutes.

 

[insco2]

alright.. i have heated my strike water up in the test simulation and i have transfered to the mashtun. now im waiting on the thermocoupler to level off and i will start the at. stay tuned...

 

[insco2]

i set the atdu to 10 and it passed it and stayed in at mode. UURRRRR!!! going to try to adjust the pid like you said and see what happens..

 

[kladue]

Has the "OUT" light been cycling at the setpoint, you have to wait until the "OUT" light begins to cycle on and off before starting auto tune. Watch the PV value and make shure the controller PV and SV values are matching and the OUT light is cycling.

 

[insco2]

okay, i finaaly got the controller to finish a at cycle and it took about 40 minutes. this is what it came back for my system.
p=.04
i=1710
d=399
sous=0
ot=002
the only problem is the device still wants to undershoot the target temp. what would be the proper setting to raise this value?
my heat exchanger is a 5 gallon gott cooler witha 1500 watt element. i know that that is enough element for the job. so to prove my theory i just plugged the element into an outlet and sure enough it brout the exchanger up to the desired temp. now i just need to figure out the proper seting for the pid.

 

[kladue]

It sounds like you have a gott cooler with an element in the side and a thermocouple or sensor through the lid. With 5 gallons of water and no circulation the response is going to be real slow, shown by the "I" time of 28.5 minutes. Here are some suggestions for an initial manual setup for the PID values P=20, I=180, D=45, SouF=.2, Ot=10(this will increase the minimum on time to 10 seconds). After setpoint temperature is reached watch the time between PV peak values, this is what you need for the I parameter, again use 25% of I for the D parameter. If the controller keeps overshooting the temp then increase Souf by .1, if not overshooting then reduce by .1. With the quantity of water and 1500 watt element you should hit 1.8 deg rise per minute if stirred to distribute heat input, if you are letting the thermosiphon effect distribute the heat then it will be slow to change temperature and harder to control.

 

[insco2]

this is the thermocoupler.

through the wort pump.

through the gott cooler with the heating element.

do yoyu think it would be a good idea to have a mixer in the cooler circulate the water?
I brewed yesterday and the system didnt do bad it still wanted to undershoot a little.

 

[kladue]

Nice looking setup, looks like you are trying to control the element with the mashtun leaving temperature. Here are a couple suggestions for your current setup, use a controller for the gott cooler that cycles the element to maintain 170 deg, something to stir the water to improve the heat exchange process, and a 3 way solenoid piped as close as possible to the heat exchange coil outlet. Use PID controller to open/close solenoid and leave pump running continously to allow sensor to monitor temperature. The element controller does not have to be precise or expensive just able to maintain the temperature around 170 Deg, watch Ebay for a Ranco or Johnson but watch out for manual reset models as they have to manually reset after reaching setpoint.