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Are the temperature adjustment knobs on most high-power AC (infrared or radiant) heaters just standard potentiometers, the same that would be found in low-power DC devices? I'm asking about the knobs that go from "low" to "high", not ones that list a specific temperature (like "76F").

More information (in response to comments):

I haven't yet opened the actual heater I'm referring to (it's difficult), but coincidentally I chanced upon an already-opened radiant heater and took a picture of the back of the knob and the internals. heater internals overview

What do you think it is? Is it safe to assume that a similar device is controlling my 1,500 watt IR heater? It's difficult for me to open the 1,500 watt unit, otherwise I would have done so already.

(I tried to post links to the heaters, but it wouldn't let me because I don't have enough reputation).


UPDATE: I finally took apart the IR heater that I was originally referring to. Sorry it took so long. It wasn't easy.

Here is a picture: heater pot

I tested the resistance on the 2 contacts, and it starts at 260K at the lowest setting, ending at around 80ohms at the highest heat setting.

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  • \$\begingroup\$ The knob itself may be a standard potentiometer, assuming that the control is stepless. The actual power however will always be regulated in some other way, probably using a TRIAC. \$\endgroup\$ – jippie Aug 15 '15 at 16:18
  • \$\begingroup\$ Not identical but pretty similar: electronics.stackexchange.com/questions/65574/… The animation shown is with a rectified sine wave whereas "your" heater will probably not be rectified. The mechanism however is the same. \$\endgroup\$ – jippie Aug 15 '15 at 16:23
  • \$\begingroup\$ Does the IR heater adjust smoothly or does it cycle on and off? The one you posted photos of uses an electromechanical method. \$\endgroup\$ – Spehro Pefhany Aug 17 '15 at 19:44
  • \$\begingroup\$ I'm sorry I overlooked that point. The one pictured above cycles on and off, but the 1,500 watt IR heater "dims" the heating element instead. It doesn't cycle on and off. \$\endgroup\$ – Jerry Aug 17 '15 at 19:48
  • \$\begingroup\$ The picture looks like some version of the mechanism that I described. Something that "dims" is more likely to use an electronic voltage adjustment scheme with a potentiometer, but you won't know for sure without examining it. \$\endgroup\$ – Charles Cowie Aug 18 '15 at 4:07
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It's a potentiometer that adjusts the firing angle of an SCR.

An SCR can be used as an inexpensive controller for a heater, by adjusting the firing angle you are controlling how much power is delivered to the heating element. SCRs only work on half the cycle. To gain a bit of efficiency, but also complexity a triac can be used. It will work like an SCR, but on both the positive and negative cycle.

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  • \$\begingroup\$ Thanks. I marked this as correct because it seems to match my situation. Can anyone please tell me what would happen if a value lower than the lowest setting on the pot was used? For example (hypothetically): the lowest setting on my pot is 260K, and I'm wondering what would happen if I put a 470K resistor there instead. Would the heat output of the heater become lower than the previous lowest setting? I'm not educated enough about this topic in order to know how to search for a relevant answer. \$\endgroup\$ – Jerry Aug 25 '15 at 6:48
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I don't think so. I think they are usually more like a thermostat for central heating and air conditioning. They mechanically adjust the operation of a bi-metallic device that opens and closes an electromechanical switch.

Edit In order to have more than some conflicting opinions, you might post a picture of the type of device that you are asking about. Can you determine if there is some kind of electronic power control circuitry. Is this a plug-in portable heater of some kind? It seems to me that any heater that is controlled by a "high-low" knob is unlikely to have anything but an on-off control scheme.

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  • \$\begingroup\$ I will post a picture of the internals soon, as well as a URL to the device. I wasn't planning on opening the unit if the answers here said it wasn't like a regular pot. But since there are varied opinions, I would really like to know what it is. \$\endgroup\$ – Jerry Aug 15 '15 at 19:26
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Yes, but not in series with the heating element, but rather to control the switching of a Triac. http://www.learnabout-electronics.org/diodes_07.php gives an overview how these circuits typically work.

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  • \$\begingroup\$ Please edit some information from the link into your answer. As it stands, this is mostly a link-only answer, which is discouraged since the link may not always work. \$\endgroup\$ – Null Aug 15 '15 at 18:47

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