DC Thermal Induction? - Page 1
Forum section: electronics / beginners

author: THATguy
author_rank: Regular Contributor
timestamp: February 05, 2017, 09:22:47 am
content: Is there anyway to make a low power DC Thermal Inductor? (with a tiny coil)Close down the DC, then send the DC back in referse - or am I just creating AC? But I guess I couldn't do that at low power?How about two separate Inductors next to each other, the opposing one has the current going through the coil in the opposite direction.To stop the coils from picking up each others magnetism, I'd surround them in magnet shielding.(The stuff they have on the back of harddrive magnets - it allows the magnetic fields to flow through, but not outside.)I'd probalby still need a lot of Watts for this.Here are some good points:"How is generating high-power, high-frequency DC pulses any easier than building "an inverter"? The only difference is a DC-blocking device such as a transformer or a capacitor.""How fast are you able to switch the DC input? You probably need to reach the kHz range for it to be useful."Taken from this post:http://electronics.stackexchange.com/questions/153321/can-pulsating-dc-be-used-for-induction-heatingIn this article they are using 5A from a 15v source - which is pretty low, their inductor looks small.http://www.rmcybernetics.com/projects/DIY_Devices/diy-induction-heater.htmThis guy has 12v Lead batteryI'd need to water cool the inductor coils, and use something such as Tantalum/Halfnium/Tungsten wire etc etc.I only want to heat objects about 1mm diameter. Perhaps I'm wasting my time even thinking about this and should make a mini blow torch.How crazy am I?

author: ebastler
author_rank: Super Contributor
timestamp: February 05, 2017, 09:26:55 am
content: You are losing me...What the heck is a "thermal inductor"?!

author: ebastler
author_rank: Super Contributor
timestamp: February 05, 2017, 10:16:14 am
content: Let me elaborate on my somewhat curt question above:Are you simply looking for inductive heating? In that case, the term "thermal induction" is not commonly used. And no, induction does not work with DC currents. What's wrong with AC?Or are you after the somewhat elusive subject of the equivalent of an inductor in thermal systems? In that case, what are you trying to achieve? Are we on the slippery slope to free energy and a perpetuum mobile here?

author: THATguy
author_rank: Regular Contributor
timestamp: February 05, 2017, 10:20:21 am
content: I have an induction cooktop.There are inductors who's purpose is not to induce heat per se.If you look at the links you'll see what I'm talking about (if I used incorrect terms).I figure I nead loads of current for AC? That's why.I prefer DC and very low current devices. It's my thing.Haha, no no, though I am a fan of mV harvesting of "FREE" energy from environmental radiations - though it won't get you far, infact rubbing your head with a piece of plastic will get you more free energy (if you have hair)

author: ebastler
author_rank: Super Contributor
timestamp: February 05, 2017, 11:02:17 am
content: Quote from: THATguy on February 05, 2017, 10:20:21 amBoth, your induction cooktop and the 12V/5A system in the link you shared, use AC of course. Not plain old 50Hz (or 60 Hz, depending on where you are), but higher frequencies, which introduce the heat-generating eddie currents more effectively.If you start with a DC voltage, then switch its polarity back an forth, or toggle it on and off, you have an AC signal. And AC is required for any induction effect -- whether you want to generate heat, induce voltage into another coil in a transformer, or are interested in the voltage/current behavior of an inductor to build a filter or whatever.QuoteThe required power depends on what you want to heat, of course (what thermal mass, and what losses to the environment), and how fast. The example setup you shared uses 60W to heat a screwdriver tip to glow red-hot in 30s. Nothing magic about that; my soldering iron heats its tip much faster, using simpler resistive heating. And the light bulb in my bicycle's tail light even gets white-hot in fractions of a second, only needing 0.6W ...Come to think of it, maybe you are really implying 50Hz when speaking of AC? In that case, yes, that's not the recommended way to obtain efficient inductive heating; one should use much higher frequencies. But "very low current" will still imply low heating power; obviously you don't get more heating output than the electrical power you put in.

author: THATguy
author_rank: Regular Contributor
timestamp: February 05, 2017, 08:46:12 pm
content: Yeah, I guess if something is built as small as a light bulb filament it would be generating photon heat or even plasma.And in that case I may as well just use lasers, Or a micro gas torch.

author: james_s
author_rank: Super Contributor
timestamp: February 05, 2017, 11:05:16 pm
content: A light bulb filament is a resistive heater, current passes through it directly and it gets hot because its resistance drops voltage and dissipates it as heat.Inductive heating is a completely different principal, it requires AC, inductors don't do anything with DC, they just act like a piece of wire.The amount of heat you get is proportional to the amount of power you put into the system, there is no way around this. A small light bulb filament takes little power to get white hot because it has a very small thermal mass.