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# Handwarmer made out of PCB copper?

#### Flyback

##### Well-Known Member
Hi,
We are making an egg-fryer from a 7cm x 7cm PCB. (single sided, 2 oz copper covered with conformal coat), It will have a 0.5R resistor made on it with PCB tracks.
If we put 10A through it, how long will it take to heat up the copper to 180degC? (ambient is 25degC)

#### Lightium

##### Member
It's a balanced equation. Research electric heating of a mass.

#### Kerim

##### Member
I guess you have an idea about the cross section of the copper track to find out its current density (A/mm2) at 10A.

#### For The Popcorn

##### Active Member
If you search "pcb heater design" on YouTube, you'll find several guys who have experimented with designing pcb heaters for several different applications.

#### alec_t

##### Well-Known Member
If we put 10A through it, how long will it take to heat up the copper to 180degC? (ambient is 25degC)
Heat input = Watts x time.
Heat required = mass (m) x specific heat (sh) x rise in temperature (dt).
You need to know those parameters for each of the components of the system and also take into account insulation below the heater panel.

#### Pommie

##### Well-Known Member
Your putting 50 Joules into your copper ( I²R = 10² x 0.5) That will give a ~150°C rise in one gram of copper in one second and it'll keep going until it melts. However, the weight of your copper is unknown (to us) and the rate of heat loss is also going to be a big factor.

Mike.

#### Tony Stewart

##### Well-Known Member
It will take a lot longer to heat up an egg with 50 Watts than just the 2 Oz copper track which serves no purpose.

#### Flyback

##### Well-Known Member
Thanks,
...it seems to heat up almost immediately.

Possible help -

Regards, Dana.

#### alec_t

##### Well-Known Member
We are making an egg-fryer
That's some serious hand-warmer (per thread title).

#### Tony Stewart

##### Well-Known Member
The eggs do make a mess with a slight epoxy taste.

I've tried a hand warmer Lipo Glove. They are terrible even at 0'C and expensive. But mitts work fine due to the superior insulation.

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