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Comment by laumars | Hacker News Reader

I thought that when I first switched to induction. Then I realised that induction responds instantly to any changes you set in temperature so you don’t need to move the pan about in 3D space, just leave the pan on the stove and drop the heat right down.

I’m now back on gas after a house move and I miss induction so much.

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> I realised that induction responds instantly to any changes

Hmm... My electric hob seems to control temperature by the amount of time the heating elements are active (+presumably a thermostat). There's a red light when the heating elements are active (or hot but switched off), and a definite click sound when the heating elements come on. You can see the heat immediately turn on when you change to a higher temp, and when you change to a lower temp it seems to just leave the application of heat off longer (I guess allowing elements to cool down to whatever the thermostat says they should be).

What you have is resistive electric stove. It is not the same as an induction stove.

Right, but duty cycling is a common method of output control. I've seen induction cooktops (presumably cheap ones) that also has the same behavior.

Sure all inductions jobs will use duty cycling (pulse width modulation if we’re getting technical). But that doesn’t determine responsiveness.

With a resistive hob (ceramic hob is the industry name) you’re relying on a large lump of stone (hence the name ceramic hob) to be a heat store and even out the elements lumpy power output. Problem with this approach is that it takes forever for the stone to heat up and cool down, so the hob is slow to respond.

With an induction hob, your heating pan directly with a electromagnetic field, the only thermal mass in the entire system is the pan. The hob can instantly change its power output, because its not relying on a stone to store energy, and thus has zero thermal mass.

So induction hob react at the speed of your pan, you have lightweight pan, then the pan temperature will change almost instantly. You got a heavy cast iron pan, then the pan will take a little longer to shed the extra heat.

FYI: If the hob glows when heating, it’s not induction. It’s a ceramic hob. Ceramic hobs are crap and give induction hobs a really bad name because the look the same when off. You can only tell if an induction hob is, if there’s a pan on top. They’re incapable of creating heat without a pan on top.

>inductions jobs will use duty cycling (pulse width modulation if we’re getting technical). But that doesn’t determine responsiveness.

It absolutely does when the pulses are on the order of ten seconds long, as in many electric ranges. But yes, the thermal mass of the heated coil/cooktop are also a major factor.

No it doesn’t, because change the ring setting will interrupt the current duty cycle, and terminates it early if it needed. A control system that didn’t do that would be more complicated than one that did, because it would require the control system to persist internal state across duty cycles.

Sure, in the limited sense of immediacy of response to change in control input. But in the more general sense of also considering accuracy/consistency of response to a control input, not so much. If you have a low thermal mass pan on a middling heat setting on a hob with excessively wide pwm like that, you can tell when the hob is on and when it's off just by how much the contents are sizzling any given second. The pan temperature is not stable because the pulses are too wide.

I’ve personally never encountered such a poorly designed induction hob. Induction hob require proper electronic control systems to operate, it would be weird to design such a system to operate with a wide PWM, it’s costs nothing for the system to operate at 1Hz or higher.

In ceramic hobs, they usually don’t have proper power control systems. They normally rely on a set of thermal switches to disconnect the main heating element when the ceramic element gets hot enough. The entire control system is analog and relies physical phenomena like wax expansion etc. Phenomena that is well know to be unresponsive, but very cheap.

My induction hob does similar on low power settings (at the lowest it's something like 1 second on to 4 seconds off). On higher power settings it's not noticable. I suspect the main reason for this is it's often harder (and more expensive) to design power electronics to operate over a wide PWM duty cycle efficiently, so the low-speed cycling is a way to provide the low settings without a significant cost increase.

Induction hubs are electric but not all electric hub are induction. I’m not certain what you have there, sounds a little like halogen zones though those are old and uncommon.

Induction doesn’t work by producing heat. It works by using electro magnets to excite the metal pots causing them to heat. This makes induction much more efficient than conventional electric (more efficient than gas too) but also fast to react to adjustments in heat settings because you’re not relying on conduction.

https://www.ukwhitegoods.co.uk/help/buying-advice/cooking-pr...

Yeah, no idea either, I rent my current place so it's just whatever the landlord put in years ago and there's only a brand name but no model number on the hob itself.

EDIT: from the link, a ceramic hob matches most closely

Yeah ceramic hobs are one of the, if not the, worst types of hob you have. I feel for your pain there because my first house had them and I found them to be borderline unusable.

>just leave the pan on the stove and drop the heat right down.

I still lift the pan to cool things a bit on an induction top; most units will give you 2 or 3 seconds before auto-off when you do so.

Why you may ask? My cheap induction hob has slowly failing membrane keys.

I can believe it, maybe I've just only used bad induction.

Or more likely bad pans ;-)

My wife and I have a $200 two burner induction cooktop (Duxtop) and it definitely leaves a bit to be desired. You can tell it tries to keep temperature as conditions change, but it definitely struggles, and the adjustment is pretty coarse. I imagine $1500 Breville one someone else mentioned here is a different experience!

I bought a cheap (£200) 4 plate induction hob around 10 years and it worked really well most of the time (it only struggled if you tried to have all 4 plates on high temperatures so you’d have to think ahead a little if doing a roast). But if 1 to 3 plates running concurrently it was really reliable. So you don’t need to buy top end to get something useable.

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