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MorePies
Stranger
Registered: 02/09/16
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Loc: TX
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Need help programming PID controller
#23885457 - 12/01/16 06:45 PM (7 years, 1 month ago) |
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Hi!
I have recently built a 55 gallon super pasteurizing barrel to run my supplemented sawdust bags through. It's a 5000w element controlled by this controller. It's my first time using a PID controller and I have a few questions. My current issue is boiling super hard and nearly running dry after 6 hours. If anyone can recommend where I can find how to put in a sight glass, that would be really helpful! My intent is to get this controller to get the bags up to temp, start a countdown timer, then open the relay to stop powering the heating element. I am confident that I know how to program the timer function, it's getting there that's hard! Here are my questions!
Should I use autotune to set the P, I, and D values?
Instead of using it as a PID controller, should I use the device in on/off mode and manual mode so I can adjust the power output to x% to maintain a slow boil?
Should my set value be 100 degrees C?
Are there other questions I should be asking?
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Gr0wer
always improving



Registered: 09/16/03
Posts: 6,056
Loc: El Paso, TX
Last seen: 5 years, 10 months
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Re: Need help programming PID controller [Re: MorePies]
#23886230 - 12/01/16 11:21 PM (7 years, 1 month ago) |
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Yes you will want to autotune. Your setpoint shouldnt be just 100c, you need to see what boiling reads at your elevation and set it a degree or two shy of that. I dont want to tell you specific settings as i havent read that manual yet and im not sure how it programs compared to my models. You dont want a sight gauge but put a stainless steel float switch to open the ssr control circuit when the water gets too low. This is why i use a float valve to maintain the minimum water level and only a 1500w element so no pid or temp control of any type is needed, just a $20 24hr outlet timer. Print out the manual for your PID if you havent already. If you need more help after reading it and playing with you controller pm me, i have a few of there PIDs including two of there ramp soak ones which are a model higher than the timer one. I use one to control my automated aa941 and the other for my brew rig.
Edited by Gr0wer (12/01/16 11:24 PM)
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MorePies
Stranger
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Posts: 808
Loc: TX
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Re: Need help programming PID controller [Re: Gr0wer]
#23889112 - 12/02/16 09:39 PM (7 years, 1 month ago) |
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I went with the PID route because I didn't know there were others and I definitely didn't want to be powering the water heater element constantly. I should look into a float valve and another pre-heat barrel like you have, or just tee off from my washing machine hot water line as it's nearby.
I did set it to autotune as it hit the 99 degree C mark and upon completion it really helped limit power use while maintaining the temp. of 100 degrees accurately. My PID does not have a ramp function to it, so the work around I'm contemplating is to plug it in and let it run on full to achieve a rolling full cauldron of inferno boiling. Then shifting it to manual to operate on 50-60% power. When it's around 90 degrees C, switching it over to PID mode as it has autotuned to operate during those late stage temp gains. Once it hits its set value temp., the timer starts and after 10 hours it disconnects the relay.
Is 6 hours to hit temp and 10 hours at that temp sufficient for a mix of 5 and 10lb bags?
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drake89
Mushroom Magnate



Registered: 06/26/11
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Re: Need help programming PID controller [Re: MorePies]
#23889219 - 12/02/16 10:24 PM (7 years, 1 month ago) |
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You need a temp probe yourself
If you don't have one stc 1000 is $15 and works well if you have a relay
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MorePies
Stranger
Registered: 02/09/16
Posts: 808
Loc: TX
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Re: Need help programming PID controller [Re: drake89]
#23889253 - 12/02/16 10:37 PM (7 years, 1 month ago) |
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Hi Drake, I don't quite follow. I have an auberns pid, and it is wired through a 40amp relay with a type K thermocouple.
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drake89
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Registered: 06/26/11
Posts: 4,168
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Re: Need help programming PID controller [Re: MorePies]
#23890091 - 12/03/16 09:53 AM (7 years, 1 month ago) |
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Quote:
MorePies said: Hi Drake, I don't quite follow. I have an auberns pid, and it is wired through a 40amp relay with a type K thermocouple.
your last question was regarding how long it will take to get your bags up to temp. it's just something you have to find out yourself on your own rig. it will take almost twice as long to bring 10lb bags up to temp so it might be better to run them separately.
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Gr0wer
always improving



Registered: 09/16/03
Posts: 6,056
Loc: El Paso, TX
Last seen: 5 years, 10 months
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Re: Need help programming PID controller [Re: MorePies]
#23890092 - 12/03/16 09:53 AM (7 years, 1 month ago) |
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You dont need the ramp soak, read the manual. From the item description i see there is a mode that gets it up to temp then starts a timer and shuts down when done. You could even have the alarm relay go off once the target temp is reaches that opens a soleniod valve draining the hot water tank into a 2nd straw tank then once the process is over set off the other alarm relay to open the straw drain valve and end process. I think between the two alarms and ssr output you could completely automate the process. Read the manual a few times if you havent already.
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Gr0wer
always improving



Registered: 09/16/03
Posts: 6,056
Loc: El Paso, TX
Last seen: 5 years, 10 months
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Re: Need help programming PID controller [Re: Gr0wer]
#23890130 - 12/03/16 10:04 AM (7 years, 1 month ago) |
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You would also want a float switch just above the element that breaks the power to the control side of the SSR. This will protect your element from dry firing.
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MorePies
Stranger
Registered: 02/09/16
Posts: 808
Loc: TX
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Re: Need help programming PID controller [Re: Gr0wer]
#23890289 - 12/03/16 11:18 AM (7 years, 1 month ago) |
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Thank you grower. I'm not working with straw, but I see how it would be efficient to capture that hot water from a sterilization run. I'll look into the float switch and stainless float valve to protect the system. I did read the manual a number of times before, during, and after posting, I just wasn't feeling like I understood it well enough.
Edited by MorePies (12/03/16 11:19 AM)
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Gr0wer
always improving



Registered: 09/16/03
Posts: 6,056
Loc: El Paso, TX
Last seen: 5 years, 10 months
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Re: Need help programming PID controller [Re: MorePies]
#23895081 - 12/04/16 08:02 PM (7 years, 1 month ago) |
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Use the stainless floats from ebay that goes for around $25, its legit.
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