Resistors for a dew controller

[Photosbykev]

Hi folks,

I'm partway through building my own all sky camera using a Watec 902H2 Ultimate or 910HX camera and fisheye lens with a 4" acrylic dome and plan on using some resistors to keep the dew off the dome and lens. Has anyone had some practical success with this approach rather than playing with dew heater straps. I'm looking for some typical resistor values running from 12v or what sort of watts of heat are required to keep it clear.

regards

Kev

[Alien 13]

I would tend to work on the principle that the system would need vairiable control so if we said the most likely max would be about 6 watts then the total current would need to be 500mA, from this using a  DC-DC convertor you would be able to get between 500mW up to the max of 6 watts.

The total resistance value would need to be 24 ohm and the power rating for each resistor would be 6/number of resistors used in series.

A typical setup might use 6 resistors in series so each one would be 4 ohms at 1 watt.

The standard type of 3A DC-DC converter like this would do http://www.ebay.co.uk/itm/5pcs-LM2596S-DC-DC-Buck-Converter-Adjustable-Power-Supply-Step-Down-Module-UK-/141210161794?pt=LH_DefaultDomain_3&hash=item20e0c81282#ht_1108wt_1147

Alan

[Gina]

Using resistors is how I plan to make mine but it's not built yet   I'm also planning to run off 12v (or 13.8v) and use 3 resistors.  I'm hoping to get round to finishing it one day

[Photosbykev]

Thank you Alan, very useful information

[Cath]

You can also do a parallel-series arrangement if you prefer to use smaller lower wattage resistors - which could also make it more strap like in construction rather than bulky-bumpy.

You might find this helpful too ..

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

[Photosbykev]

You can also do a parallel-series arrangement if you prefer to use smaller lower wattage resistors - which could also make it more strap like in construction rather than bulky-bumpy.

You might find this helpful too ..

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

Thank you Cath