Current/heat dissipation control in an R-L circuit

[dynamo]

Hi all,
I am working with a coil made of 14AWG wire.
There are approximately 60-70 windings that are 12" in diameter.

The resistance of the coil is 0.6 OHMS.
I am using 12 Volts DC @ 5A power supply.

I have put a 10 OHM 50 W resistor in series with the power supply and coil windings.
My problem is that the resistor is generating an awful lot of heat if I leave the current on for too long.

I have added aluminum heat sinks that seem to help a little, but still the resistor gets up to 190 degrees F when I leave the current on for long times, say 10 minutes.

Is there another way to keep the current constant to say, 1A, without using a resistor?
My goal is to create a steady DC magnetic field so I prefer a simple circuit without using high frequency switching, if that makes sense i.e. to use only DC, not pulsed, if possible.

As an aside, I don't understand how the 12V 5A DC power supply can stay so cool, even if I draw 4A from it.
I presume because it is a switching power supply?
It is like a laptop or LED lights style power supply, as in the image below, just FYI...

Thanks in advance for any ideas!

 

[(*steve*)]

I recommend you increase the number of turns to about 1300.

 

[duke37]

Your DC power supply uses high frequency switching.

 

[CDRIVE]

If you insist on using linear technology you won't be able to escape the laws of physics. Whether it's a resistor or a solid state current limiting device it's going to dissipate the same heat. That's why switch mode power supplies are soooo popular. The pass component is either fully on or fully off. This leaves the low ESR filter cap to do all the work without generating a lot of heat .

Chris

 

[dynamo]

Thanks all, great replies and info.
I may have to resort to more turns as *Steve* suggested, although with smaller gauge wire, to get the resistance I need from the coil and therefore hopefully eliminate the resistor.
I will try 18AWG, 20AWG or 22AWG and see what happens.
I'll measure the resistance of say, 100ft. of 18AWG, then extrapolate from there what length would give me 10 OHMS or thereabouts...
I guess the coil will not get as hot as the resistor I'm presently using since the coil is such a large surface area compared to the 50W resistor?

 

[BobK]

For 1.2A you could go as low as 28AWG and you would need 49 turns. For 26AWG I get 79 turns.

Bob

 

[dynamo]

For 1.2A you could go as low as 28AWG and you would need 49 turns. For 26AWG I get 79 turns.

Bob

Thank you, BobK, excellent information!

 

[dynamo]

Update...1000 feet of 20AWG (MTW) = 10 Ohms resistance.
300 feet gives me about 4 amps using 12Vdc, well within the limits of my power supply.
Thanks all!