Induction cooktops, temperature control questions

I assume with gap-pad you mean the stuff used to heatsink SMT transistors et cetera to a nearby chassis panel. I wonder if that could take the heat of a red-glowing spiral burner section. Then I could just use my cooktops but have better heat coupling.

Lasse's idea of a heat jacket is a good one. I'd have to find a 3rd 120V circuit nearby though.

I'd have to bring that, it doesn't travel well or would the need a week of rest for the yeast residue to flocculate back down.

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Regards, Joerg 

http://www.analogconsultants.com/

On May 24, 2019, Joerg wrote (in article ):

in a ring, and measured in the center, well away from the heat path. Sort of like a 4-wire resistance measurement.

I did come across one reasonably priced induction hob that claims to have

100-step power control. I bought and tested one of their models (PIC Gold), and the 100-step claim is plausible. It is certainly far more than ten levels, which is maddeningly coarse even for ordinary cooking.

Confusingly, they talk of four power levels: these are selectable maximum power draw levels, so one can use the same hob in a house (full 1800 watts), or on a RV or a boat (far less is available), without blowing breakers.

The induction hob in question is called NuWave and is made by Hearthwave, Inc in Libertyville, IL 60048. NuWave LLC seems to have been stood up for this business area.

PIC Pro ($180) is 1800 watts max: .

.

Their patents are useful for somewhat more technical detail than user-manual level, but are also a bit confusing.

NuWave induction cookware gets very bad reviews. European cookware rated for induction works well.

Joe Gwinn

The power levels are nice, many have six or more. This one has 10 settings:

There are two things that manufacturers generally do wrong. They do not provide power levels in the 100W range so you can't easily use the cooktops for slow-cooking. Then the temperature control granularity is way too coarse which makes them less useful for brewing, pasteurization and many industrial processes. Both could easily be provided at zero extra cost.

Their temp control happens at 10F granularity which unfortunately is too coarse for brewing.

Derek Decker in a brewing NG suggested an interesting cooktop:

I'd have to inquire but it seems this might be controllable in 1F increments and even has an external sensor. The alternative would be to hack a regular induction top and have an external loop. With some hysteresis I could hang a FET opto-coupler across the built-in center thermistor and fool it into believing the temerature has been exceeded, which woud turn it off until I let go.

That still leaves the question how far the steel plate could be from the cooktop. Jan's experiment was encouraging, he held the pan about half an inch away in the air and it still cooked an egg. He forgot the bacon though ...

We've had a sort of radiant heat cooker here from a friend. It had a big pot and the heater unit was in a thick lid. Wasn't impressed. The quality was ok, just the general idea of cooking that way wasn't, IMHO.

I have relatives there so someone could bring it when visiting. It's not a slam dunk though because most are rated 230V and our two-phase easily goes to 255V for hours. I could use a 24V step-down but that starts to get old.

--
Regards, Joerg 

http://www.analogconsultants.com/

I use a soft, gummy silicone stuff from 3G Shielding, about 6 w/mK, pretty good heat conductor. The data sheet says 160C max.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

That would be greatly exceeded at the spots where the coil glows red.

--
Regards, Joerg 

http://www.analogconsultants.com/

Yes; that gobsmacked me.

The first single "ring" portable induction hob I bought my mother (at 95 she was worried about a gar ring setting her sleeve on fire) had exactly that problem. IIRC it was ~400W minimum, so it couldn't even simmer a sauce!

It went straight back for a refund.

After some homework, the next one is just fine in that respect, although it has more controls/options than desirable for a 97yo. Example: the manual states that on the "boil" setting, it will boil for "a while", grrr.

If Widmer Hefeweizen is on tap, that's my favorite. For bottles, though, fresh matters more than other qualities; in SF, I go with Anchor Steam.

In taste-testing while in college, the least expensive local brew was preferable (because in the vicinity of campus, it was always moving off the store shelf, so was always fresh).

On May 24, 2019, Joerg wrote (in article ):

provided

The Walmart unit has only ten distinct power levels, far too coarse for even ordinary cooking.

.

This is a kind of Sous Vide unit. I do have an older Anova unit with 1F granularity that falls between the $50 junk and the $1000 restaurant equipment. Here is a current offering I received in February (but the link still works):

.

The occasion was to announce that Anova is being acquired by Electrolux.

restaurant.

beer mash, instead using the heater to keep a water bath at temperature, with the beer in a pot sitting in the bath.

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I never knew that pots and pans also were rated for mains voltage ranges in Europe.

Joe Gwinn

The power levels would be ok if they offer some below 200W for slow-cooking. The temperature is the problems. Standard is 40F increments (useless) and occasionally 10F increments which is still not ok for some jobs.

Can't because the lid must be mostly closed or you can't keep a boil at the available power level. Also, the innards would crud up unbelievably.

The I'd need an even bigger pot to hold my monster pot. That's not going to work. Immersion can work and some brewers do it but the stick has do be completely without cavities, must have easily cleanable surfaces everywhere and unfortunately it really gets in the way when stirring.

They look like this:

Most are 240V, are in the 4000-5500W class and you have to use an external temperature control loop:

Key is to have a good old analog thermostat or, if it must be digital, have 1F granularity.

Sometimes they have that built in. We've got wome but now all American, after moving here from Europe.

--
Regards, Joerg 

http://www.analogconsultants.com/

On May 25, 2019, Joerg wrote (in article ):

1kW

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Even with ordinary gas or thermal electric (non induction) hobs, this is a problem. Sellers talk only about max power out, and less about controllability, and almost not at all about being able to simmer with any control. It takes an expensive unit to do all these well. I recently replaced a gas stove, and simmer was a big need. The solution was an electronic module that turns the flame on and off periodically. This gets around the limited dynamic range of a burner, maybe 9:1 for a very good unit.

s

How big is this monster pot? There are pots big enough to cook missionaries.

The difference is between cooktops (with hobs) and cookware (pots and pans, only some of which can be heated by an induction hob).

To my surprise this works very well on the $10-12 Walmart electric coil cooktops. I can set one to slightly above "1" and it'll hold 156F to within +/-2F, good enough.

It's got 16-1/2" or 42cm diameter. It could not be half an inch shorter or it woudn't straddle my two cooktops.

Ok, here I meant the cooktops, of course. The pot presents another problem as mine isn't induction-suited.

--
Regards, Joerg 

http://www.analogconsultants.com/

On May 26, 2019, Joerg wrote (in article ):

KISS wins. That electric-coil unit must have a control with more than ten steps, but with only ten levels marked.

What I did in the old days, when electric-coil hobs had four settings (including off), was to use such a hob set to full power, but driven from a variac. Now days, one would use a solid-state variable power control intended for a hot tub.

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How deep? I have some dutch ovens that large, but no stockpots.

.

Joe Gwinn

No steps and that's just the trick. It's totally analog, a bi-metal thermostat with a worm gear and a knob. In digital that could easily be emulated at zero cost but they don't do it.

A big dimmer would suffice. With electric burners it's not needed because even the cheap ones have nice analog controls. That's still not as good as a thermostat though because these cheap cooktops really regulate the coil temperature and thus (indirectly) the temperature at the bottom of the pot. On cold and windy days outside I have to set it slightly higher and it still works.

Total volume is 13 gallons, it's pretty deep.

That's my issue, the brew kettle is not induction-suited so if I can't make that compatible with a steel plate in there induction isn't going to work. Mainly because it is tough and probably very expensive to find an induction-suited stainless pot with such a large diameter so it can straddle two cooktops.

--
Regards, Joerg 

http://www.analogconsultants.com/

Just measured it, it is 15-3/8" or 39cm deep. I am brewing an Irish Red Ale right now and currently the steeping grains are in. As usual, one of the cheap Walmart burners is holding it at exactly 156F. It just took 1h

10mins to get there. Since it's cold right now it'll be well over another hour to get from there to a rolling boil. Meaning I can't brew the 2nd beer today because I am also Mr.Barbecue later and it's a more time consuming meal.

--
Regards, Joerg 

http://www.analogconsultants.com/

It's snowing now a bit uphill from you.

--

John Larkin   Highland Technology, Inc   trk 

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

On May 27, 2019, Joerg wrote (in article ):

a y d

It sounds like what you need is acommon industrial temperature controller plus a 12-volt DC relay to turn the hob AC power on and off, replacing the internal coil-temp thermostat. Attach thermocouple to bottom of pot away from the heating coils, in a bit of aluminum pressed up against the bottom of the pot. Or have it dip into the mash fluid.

Here is a suitable unit. I buy stuff from Automation Direct, and it all has worked.

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The unit in question is a "SOLO Basic Temperature Controller", and costs $40 (not including power relay and thermocouple).

And 15-3/8" or 39cm deep, from the other email.

This is 108 pounds if full to the top.

ges

As has been discussed, one can sit the pot atop a piece of mild steel that is

electric coil, a thermocouple, and an industrial temperature controller.

Joe Gwinn

Ebay/ Amazon is your friend on this one. Large amounts of OEM Induction Co oker driver modules for sale. Some have already been hacked, except the ha cking is documented in blog posts, not wen sites, so a little difficult to find.

If you want to make your heated region an extension pipe off the main tank, we've had really good luck at the university playing with the 48V 1 KW R oyer Oscillator modules from Ebay. You cant tune them much, so you have to tune the load design. Easily heats the right diameter pipe, silicon nitride tube, or screwdriver to glowing red. They are cheap enough to be throwawa ys in the lab.

If you are really cleaver, you can design the induction heater as an inver ted / reentrant finger "Into" the tank. Some form of forced circulation wo uld be a must.

I've had a 1KW induction hob for 4 years ago, paid 75$ for it, and love it for heating dishes at parties/meetings at work, and in the local park, whe re they provide 110VAC. Not allowed to have propane stoves / charcoal gril les on the quad at the university unless you are Department Chair or above ... Induction and an extension cord got me a wink from Health and Safety.

Steve

On a sunny day (Mon, 27 May 2019 11:05:13 -0700 (PDT)) it happened snipped-for-privacy@gmail.com wrote in :

If you ever need some voltage and have no transformer at hand, then this works fine:

Use your induction heater!

The normal kitchen ones need a piece of iron, have a micro switch with magnet to detect if there is something on it I think.

I had to brew inside and we had the wood stove going. At the end of May! I want my fair share of global warming!

--
Regards, Joerg 

http://www.analogconsultants.com/