Quote:
Originally Posted by peter_4059
That should do the trick Steve - how many Watts are you putting into it to keep things clear?
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Pete, I can't say what will work from high humidity QLD, I can only
tell you what worked for my location.
I know you have a similar DSI casing metal cross sectional area so
this may work just as well for you...dunno...anyway:
I tried 4 x 120 ohm resistors (1/4 Watt) in series on 12v at 100% duty PWM.
I calculate 25mA and 75mW. Well under the 1/4 W rating of the
resistors. This made no difference on the dew on the night I tested it.
Gentle heat given off at 12V was almost undetectable.
I then tried 4 x 68 ohm (1/4W) in series, 12v / 100% duty cycle PWM.
I calculated and measured 45 mA and 130mW power.
I could feel this heat, both before Aralditing them and after.
This worked well.
Keep in mind, this was radiating heat into a chamber the volume of a 35mm
film canister roughly. (the DSI nosepiece with Baader IR filter at the end)
Quote:
Originally Posted by rcheshire
Steve. Fantastic. That is very similar to a project I have in mind. I can't fit resistors in the space and plan on glueing Nichrome wire to aluminium tape and sticking that to the glass, then covering with black tape.
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Rowland,
I'm not too sure on Nichrome, it sounds too much like taking a sledge hammer to the problem?
This much power/ current draw might be necessary in high humidity areas
but it seems once dew is kept at bay before it forms, as you say, keeping
the area only a few degrees above the D.P. should be enough.
Unless of course it is very fine Nichrome...higher ohms /m
Resistors seem to work fine if you keep under their power rating.
Dave, thanks mate
Steve