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http://www.dewbuster.com/heaters-330ohm-resistors.html

Following this guide I made a dew strip yesterday for my Tal 100rs. The strip measures 15" long I used bare copper like the guide says and 20 x 0.6 watt 330 ohm resistors. then attached 6 amp insulated cable to one of these

 http://www.ebay.co.uk/itm/DC-BARREL-PLUG-2-1-x-5-5-mm-TO-SCREW-TERMINALS-POLARITY-MARKED-PACK-OF-1-/272267778437?hash=item3f646c9985

It feels a lot hotter than my nichrome strip. Have I messed up having a bit of trouble with the calculations thanks.

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Let's see, you have 20 330 ohm resistors connected in parallel:
1/Rtot = 1/R1 + 1/R2 + ...
So Rtot = 16.50 ohm

P = V^2/R
I'm assuming you're powering using 12V so 
P = 8.72 watts total or ~ 0.6 watts per cm.

I think nichrome is around 0.3 watts per cm so your home-made one should be twice as warm.

How were you powering it?
Note the website says:

Quote

Also, this type of heater can not be used without a controller as it would get too hot.

 

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