Phase Angle Control Vs. PID

[finmike]

Hello brewers,
I’ve been a reader of this board for some time but this is my very first post here.

I started to design my first all grain equipment and thought about automating the system as much as possible.
I’m considering between PID+SSR(on/off) and Phase Angle Controller+SSR for controlling the heating element.
PAC+SSR controlling would obviously give more control over the heating process. (possibility to control temperature gradient? Accurate temperature hold?)
But is this much control really necessary?

I have designed and built a display/control unit for completely different kind of machinery but I could definitely use it in my system for temperature reading, software PID and supplying the analog control signal for PAC.
It has TFT display, touch screen, 6 buttons, industry standard 4…20mA and 0-5V inputs, CAN-bus, USB, and PWM-signal output:

On the other hand, PID system would be so much simpler to design and build, and PID also would have less components that can break or cause trouble.
Will the PAC+SSR control bring more value to the system compared to the PID control?
I know that in some scenarios PAC+SSR can shorten life of the heating element. (Vapor phase soldering machines)


If you have opinion or firsthand experience on PAC+SSR vs. PID+SSR, I’d be grateful for any advice on choosing between PID+SSR and PAC+SSR based heating control.

Thanks!

 

[ryclo]

I think PID works very well for temp control, do you really need any tighter control than PID?

 

[jeffmeh]

A PID in manual mode provides the same functionallity as a phase angle controller. The former has a digital pushbutton interface, the latter has an analog dial interface, but they do the same thing. Of course, the PID has significant additional functionality that the phase angle controller does not have, such as the abilities to automatically reach and maintain temperature, trigger an alarm, etc. If you really care about the analog dial, then go for the PAC. Otherwise go with a PID with manual mode, like the Auber 2352.

 

[finmike]

I think PID works very well for temp control, do you really need any tighter control than PID?

Thanks for the advice.
I've seen some brewers using PAC for temperature control. While it's not a bad thing to have as much control as possible over the heating process, I was also wondering if that tight control have enough (or any) real advantage over PID.

The only practical difference I can think of would be the control over temperature gradient.. but I'm very..very new to all grain brewing and I don't have the knowledge if gradient control could be necessary or even beneficial in any situation in the process.

 

[finmike]

A PID in manual mode provides the same functionallity as a phase angle controller. The former has a digital pushbutton interface, the latter has an analog dial interface, but they do the same thing. Of course, the PID has significant additional functionality that the phase angle controller does not have, such as the abilities to automatically reach and maintain temperature, trigger an alarm, etc. If you really care about the analog dial, then go for the PAC. Otherwise go with a PID with manual mode, like the Auber 2352.

Thanks,

My intention was to implement automatical control of the PAC with my display/Control unit PID and to leave out the analog dial pot. completely.
But after thinking this over, I just realized that many brewers have used the PAC specifically for manual control(pot), and not automated.
I'm starting to realize now that PID alone has enough control..

 

[ryclo]

I use a pid for my hlt control and a pwm dial for my boil, works very well!

 

[BadNewsBrewery]

The PID is all you need. If you're thinking about automating, you may want to look at a BCS or one of the other automated systems out there that incorporate the heating phase into the automation. You cannot, to the best of my knowledge, install a stand alone PID and have it somehow interfaced with your automation system - it will require manual input by way of you pushing buttons.

That being said - the PID does great things, and holds temperatures within a few tenths of a degree. If you're looking for better accuracy than that, I doubt you'll find it with a PAC.

-Keivn

 

[jCOSbrew]

My design uses both PAC and PID and is similar in concept to the EBC III design.
* Phase Angle SSR allows analog knob to control element during boil (and mash)
* PID w/ relay output enables/disables the contactor for the element for temp control during the mash. I can set the element to 50% power during the mash.

The more common setup is to use a PID w/ manual mode + SSR for digital PWM control during the boil.

 

[kal]

I use a PID in my boil kettle to have both manual (duty cycle) control and to be able to hold or maintain a temperature too.

Many brewers only do manual control for the boil kettle but there is a usefulness to being able to maintain a temp in the boil kettle too:

- Minimize the chance of boil overs: When wort first starts to boil it foams up considerably. If left unattended (brewers are easily distracted), it will result in messy boil-overs. To avoid this, when I'm overly busy I run the PID in automatic mode with the temperature set to just below boiling (208F). I also set an alarm to sound once that temperature reached. The wort is then automatically heated to just below boiling without going any higher, and the alarm sounds. I then switch over to manual mode and continue heating while watching and stirring to avoid the initial boil over.

- Hop stands: This is something I've been experimenting with lately - steeping hops for extended periods after the boil, at specific temps (since hop oils isomerize at different temps).

YMMV

Kal

 

[alien]

Personally I do like having a manual dial for the BK. I really like the look of this controller from Swede Olsson with both PID and analogue control.

http://www.distillerycontrols.com/e...-systems/brewery-control-panel-herms-or-rims/

 

[ryclo]

For about 8 bucks you can add a PWM dail and just switch over to it when you want, here is my panel:

 

[chuckjaxfl]

If you have opinion or firsthand experience on PAC+SSR vs. PID+SSR, I’d be grateful for any advice on choosing between PID+SSR and PAC+SSR based heating control.

I think your question is broken; I wouldn't compare PAC to PID.

I'd compare PAC to PWM; and PID vs Manual control.

In all cases I'd use a PID loop to hold a setpoint, and I'd use manual control to hold a boil...vigor?

I'm not aware of any pre-built hardware PID (like the Aubers) that uses anything besides PWM to vary the duty cycle, so your SSR will be the cheaper zero-crossing kind. So, your Manual control should also be a PWM control type.

If you're using an Arduino for example for your PID, then you can certainly implement it via PAC if you like, but you'd also want your manual control side to be implemented via PAC.

Edited to add:
I just reread the OP closer. I just realized you've already written your software PID:
If that was my display, I'd keep it Fischer-Price simple:
Left-Right for MAN-PID
UP/DOWN raises ouput% when in Manual mode, or setpoint when in PID mode.


Oh, and by the way, I asked myself this same question recently. I'm going with PWM output to allow me to interlace three signals, so I can run three elements at the same time. I don't think that's doable with phase-angle.