Custom PCB Heatbed

I'd appreciate if somebody can give me information about how can I calculate (with a given layout and a specific width of the cooper core) the resistance of the PCB. I want to design my own circular heatbed for a rostock printer and need some background to build it in a correct way.
Thanks a lot

Javier

Try looking here:
[www.engineeringtoolbox.com]

Divide the areal of the trace in square meters with the resistance of copper per square meter.

In theory, a 2mm trace with 0.1mm thickness, would then be ~11.8 OHM / meter.
In pratcice the purity of the copper, and the tolerances of the PCB affect the final outcome, but it is a start.

If I remember correct 120-150W should be the lower pratcial limit for a 20x20 cm printbed.

Thanks a lot Ralf.

Also, there are some datasheets on reprap wiki that can give a good idea.. like using a big trace around the board ans multiple traces are used in parallel.. just calculate the final outcome like resistor connected in parallel.

i'm also in the making of a custom heatbed.. I need a 300x250 or so in size..

I can also add to Ralf's link, the ones that I found to be helpful in calculating traces

The CircuitCalculator.com Blog » PCB Trace Width Calculator

The CircuitCalculator.com Blog » PCB Trace Resistance Calculator

this one is a nice photo that gives a good indication of how its done: http://reprap.org/wiki/File:Big_Heatbed.JPG

Good luck :-)

Edited 1 time(s). Last edit at 02/21/2014 08:19AM by Rigor_M.

And the above pages is easier to use, and not as erronous as my calculations..

11.7 is the conductance in siemens, so it needs to be inversed.. Or easier, just swap the division and you end up with 0.085 ohms.

Quote
Ralf
And the above pages is easier to use, and not as erronous as my calculations..

11.7 is the conductance in siemens, so it needs to be inversed.. Or easier, just swap the division and you end up with 0.085 ohms.

yes, no problem, your explanation was very clear.

Thanks Rigor_M very useful links