I wanted to make a mini 12V heating element using 12 2 ohm resistors in series. What temperature will it be safe to heat it up to ? It is housed in acrylic housing which starts to melt at around 600 C
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7\$\begingroup\$ Find the datasheet and check the power rating and operating temperature. Keep in mind that your solder will melt waaaaay below 600 deg C. Consider also all other components within the enclosure. \$\endgroup\$– filoCommented Aug 2, 2018 at 8:57
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4\$\begingroup\$ If you actually make it out of 12 2 ohm resistors in series, powered by 12 V, expect 6W of heating power. I'd be really surprised if it reached anything close to 600C in any appreciable amount of time. In parallel though, you may get over 860W out, at which point you'd probably want to worry. \$\endgroup\$– Richard the SpacecatCommented Aug 2, 2018 at 9:32
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6\$\begingroup\$ Note that you might get a more even heating by using resistance wire (e.g. nichrome) instead of a bunch of separate resistors. As a bonus, there won't be any solder in the middle of the wire to melt! So you can (probably) get the middle way hotter as long as the ends don't get hot enough to melt the solder. \$\endgroup\$– Criticizing Israel not allowedCommented Aug 2, 2018 at 10:00
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3\$\begingroup\$ The melting point of acrylic glass is about 160 °C, Soda–lime glass melts at about 900 °C. What is the material of your housing starting to melt at 600 °C? \$\endgroup\$– UweCommented Aug 2, 2018 at 10:12
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3\$\begingroup\$ Also, do some math. 12V, 24 ohm load. V/R = I, so there is only 0.5A of current flow, 12V/6 equal resistors = 2V across each resistor. Power dissipated by each resistor is then P=IV = 0.5A x 2V = 1 watt. 2 Watt rated resistors would then be all that is needed. Digikey has plenty of 2 ohm, 2W, leaded resistors to select from for example: digikey.com/products/en/resistors/through-hole-resistors/… \$\endgroup\$– CrossRoadsCommented Aug 2, 2018 at 12:27
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Different types of resistor construction have different limiting temperatures.
Wirewound resistors, ceramic or metal-cased, will probably be your best bet if you want to exceed 100C.
Get the datasheet for the type of resistors you want to use, and read it.
There is the alternative of a) choose a resistor, b) turn up the power until smoke comes out, c) use others from the same batch at a lower temperature.
'Smoke comes out' can mean whatever you want it to mean. In my case, when I was testing the power handling of an attenuator I was designing, it meant a permanent change of 0.1% in input impedance after 50 overload pulses at 1 per second. No visible smoke, you just have to decide on a suitable criterion for damage.
