New Toy: Breville/Polyscience Control Freak!

[adrianvm]

Do ordinary induction cookers have  a PID controller?   If so, what are they controlling?   I suppose induction systems probably do use cycling for at least some of the different settings, which is a time nonuniformity.  Whether that's significant would depend on the cycling frequency and time constant of the pan.   Discreteness of settings on induction has nothing to do with time uniformity. 

[Laurentius]

12 minutes ago, adrianvm said:

Discreteness of settings on induction has nothing to do with time uniformity.

 For temperature settings they certainly do.

[afs]

11 hours ago, Laurentius said:

The same volume of gas, and therefore the same Btus, will be output on an given analog hob at a given setting, no matter what.  This is not the case with induction, with its discrete digital settings, cycling, PID control and standby modes.  

Just as a side note to this conversation, some induction cooktops do output a constant amount of power for a given setting.  For instance, my Vollrath HPI4 series ~3600 watt induction cooktop scales its wattage output to the % output I specify (0-100%) on the dial.  I have not checked to make sure it does not vary over time, but in my tests so far it has seemed very locked-on.

Of course it may dial the heat back if it detects a severe overheat or danger condition, etc. -- but if one is looking for constant power output there is probably an induction cooktop which doesn't "cycle" out there for them.

I personally use my Control Freaks for almost all my cooking and the low/medium/fast intensity setting has been enough for 99%-100% of my cooking needs.  But it would be really cool if Breville changed the induction drive circuitry to dial in a specific wattage output to try to maintain temperature instead of cycling a bit.  I only notice the cycling in certain circumstances and only with highly-conductive pans, and I can't remember the last time it actually affected my cooking, but it is there.

Breville, if you're listening, it would also be awesome to dial the intensity from 0-100% instead of low/medium/fast on the Control Freak.  If that intensity worked like the Vollrath HPI4-series as well, that would be a pretty killer combination.

[MJS301]

That's interesting hearing about the Vollwrath offering...I did a brief check but I don't see it as available here (Australia) but particuly interesting is the 3600w it puts out. I'm assuming that would be from a 240v outlet ? You may be aware that the CFC we get here outputs 2400w compared to the 110v version which has 1800w available. So you for you in the US that's a big difference...3600w v 1800w. Even here that's significant from the 2400w to 3600w. So, even though I can't purchase one, what do you like better about the Vollrath, you explained about the 0-100% which I agree with you on, the CFC can have a tendancy to cycle when on the upper end of intensity has been selected. Maybe you could tell us about the fan noise & controls, ease of cleaning etc vs the CFC. You indicate you do most of your cooking on the CFC ? Is the Vollwrath coil a similar size to the Breville & I notice it doesn't feature a centrol temp probe through the glass ? Is the additional probe similar to use as with the CFC...choose oil or whatever etc etc...just really curious to find out what it's all about.

[adrianvm]

I got a message back from Chefsteps support claiming that Demeyere cookware is not compatible with the Control Freak because it draws too much current and the Control Freak therefore thinks the pan is not compatible.  This doesn't really make sense to me, as I've never gotten the "no pan" message when using the two Demeyere pans I have.  Has anybody had issues using Demeyere with the Control Freak?  Or, can anybody report that they use Demeyere without obvious problems (and if so, is it the Atlantis or proline with their special induction layer, or one of the lower lines without it)?   I'm trying to decide what followup questions to ask them about this. 

[Laurentius]

23 minutes ago, adrianvm said:

This doesn't really make sense to me,

That's because it doesn't make sense.

 

What they're probably referring to is that Demeyere uses a proprietary layup called TriplInduc that optimizes efficiency on induction hobs.  The claim a 10% boost in efficiency, and the claim is consistent with my experience.

 

This effect isn't that great in cooking, but it's probably enough to goof some sensors and feedback.

 

We can't have a lack of control with a Control Freak, now can we?

[Dex]

12 hours ago, afs said:

Breville, if you're listening, it would also be awesome to dial the intensity from 0-100% instead of low/medium/fast on the Control Freak.  If that intensity worked like the Vollrath HPI4-series as well, that would be a pretty killer combination.

 

This can all be done is software, but is frankly unnecessary for users to control. It should automatically adjust the power output based on how the pan is reacting. It would prevent overshoot under low temp/load load situations automatically without the user having to adjust power level at all. Significantly harder than fixed PID/PI control which is seems to have now, but totally doable.

[adrianvm]

Actually that's incorrect.  In order for it to automatically adjust power based on how the pan is reacting it needs to know how the pan is reacting.  It does not know this.  I have just done a bunch of temperature testing (which you can see in the thread about induction friendly cookware) and have seen that the pan temperature can be 70 F higher at a point away from the center compared to the temperature reported at the CF probe.   You only know how much overshoot is occurring at the center point, but heating is away from the center, so the temperatures can be significantly different, and the overshoot can be much larger than you might think.  I cooked in cast iron this morning and butter was threatening to burn in a 6" ring while the pan reported 350 F and outside that ring the butter hadn't even started to brown.  It would appear that heating this pan evenly (if even possible) requires a slower speed than "low" but there's no way the CF can tell because at the center it was measuring 350 F. 

[Dex]

43 minutes ago, adrianvm said:

Actually that's incorrect.  In order for it to automatically adjust power based on how the pan is reacting it needs to know how the pan is reacting.  It does not know this.  I have just done a bunch of temperature testing (which you can see in the thread about induction friendly cookware) and have seen that the pan temperature can be 70 F higher at a point away from the center compared to the temperature reported at the CF probe.   You only know how much overshoot is occurring at the center point, but heating is away from the center, so the temperatures can be significantly different, and the overshoot can be much larger than you might think.  I cooked in cast iron this morning and butter was threatening to burn in a 6" ring while the pan reported 350 F and outside that ring the butter hadn't even started to brown.  It would appear that heating this pan evenly (if even possible) requires a slower speed than "low" but there's no way the CF can tell because at the center it was measuring 350 F. 

 

Because temperature isn't a scalar it's a field. Right now it can overshoot at the center too, nevermind everything else. A better algorithm would certainly fix that, and minimize oscillations. Ultimately you can't ever have complete evenness because what's in the pan is effecting it as much as the coils and the pan itself.

[adrianvm]

You're saying a better algorithm would adaptively adjust the PID parameters to decrease overshoot in the center?   It's not obvious that this is always the desired behavior.  Can you do this without making it slower?  And will it adjust quickly enough when you add food and the thermal characteristics of the pan/food system change?  The extra complexity could make it harder to use the system.  

[Laurentius]

12 minutes ago, Dex said:

 

Ultimately you can't ever have complete evenness because what's in the pan is effecting it as much as the coils and the pan itself.

 

This is a non sequitur.  You can't have complete evenness because of the Second Law.

 

It is true that food in a pan Affects the pan's evenness, but (for homogenous contents), in predictable ways.  For viscous and solid foods, and overall, measuring evenness of empty Pan A on Hob B is quite useful.

Edited May 31 by Laurentius
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