The Owls Dew Control Projects

[GTB_an_Owl (Geoff)]

Thought i would share my dew control projects with you all.

(anyone would think i had nothing better to do)


My very first effort to power my resistor dew heater straps and mirror fan was built from jaycar items which included - box, fuse/switch control panel, speed controller kit, switch and panel RCA plugs
http://www.iceinspace.com.au/forum/a...1&d=1305264146

this unit still works a treat

I decided to make a couple of new controllers using a 3 amp pre built speed controller unit off Ebay
http://www.iceinspace.com.au/forum/a...1&d=1305264146

The first build with this controller has a fused 12 volt input and a 12 volt output. Regulated output is via 7 RCA plugs. A 12 volt panel light shows the level of regulation.
http://www.iceinspace.com.au/forum/a...1&d=1305264146

An added extra is a voltage meter out of a jumpstart pack with a momentary button to check battery level.

I decided to use the 2nd controller i purchased in a no-frills version.
http://www.iceinspace.com.au/forum/a...1&d=1305264146

It simply consists of a 12 volt in and out and 4 regulated outputs with a 12 volt indicator light.

A good way to check how much power is being used -
An inline (detachable) amp meter in a small jaycar box with RCA plugs in and out.
http://www.iceinspace.com.au/forum/a...se.php?a=93956

Simply fits into the RCA lead from my battery, then on to controller unit.



Decided to use some of the many 390 ohm resistors i have on a new 2" heater strap. Followed the basic principle with the exception of using heat shrink instead of the 2" tape.
http://www.iceinspace.com.au/forum/a...1&d=1305264146

And now for something different.
Amazing what you can do with the lid off a spray paint can and the fan off a computer CPU.

Voila!
http://www.iceinspace.com.au/forum/a...1&d=1305264146

http://www.iceinspace.com.au/forum/a...1&d=1305264146

A 2" focuser fan unit for secondary mirror dew control


Hope this gives you some insite as to what you can come up with to combat the dreaded DEW

geoff

[Allan_L (Allan)]

Great work Geoff!

As you obviously have some spare time on your hands, how about inventing a 12 volt heating strap I can use in my eyepiece case ?

[Rick Petrie]

Now you will have so many more 'bits' to forget next time you go to the PC.

Good project mate and well done as I have said before.

[GTB_an_Owl (Geoff)]

Now then Allan - do you want to heat your eyepieces before - or after you use them ?

my initial thought would be to have a couple of extra (resistor) strap heaters, fed from an RCA plug mounted externally on the case (probably near the handle where it could not be damaged)

direct heat to the eyepiece you want to use next or have just used (and had dewed up) would also supply some indirect heat to the inside of the case as a whole.

how is that for starters ?

given the size of most eyepiece cases, heating the whole case, might be a bit power intensive

the other option would be to have a heated compartment in the eyepiece case along the same lines as my first option.

geoff

[GTB_an_Owl (Geoff)]

your right Rick

i now need a dedicated case/box to fit all the power/heater bits and pieces in

geoff

[RAJAH235]

Allan_L wrote...

As you obviously have some spare time on your hands, how about inventing a 12 volt heating strap I can use in my eyepiece case ?

Have you thought about using the insulated wire from an old electric blanket?
I found about 350 mm of it was about right for my eyepiece box.
You can run more than one if nec.
Just connect each to the 12 Volt supply.

Easy 'n' cheap.

[GTB_an_Owl (Geoff)]

i'm guessing that would be nichrome wire Rajah ?

geoff

[robz (Robert)]

Also known as ''RESISTANCE WIRE''
Available from Jaycar, Altronics etc.
Easier than using a heap of resistors.

[GTB_an_Owl (Geoff)]

the nichrome may be easier to use on a large diameter Robert

not so convinced on its use on eyepiece warmers though

as someone previously said - nichrome does not solder well and you need to use some sort of connector

i also had a look at electric blanket wire the other day and i thought connection wire would be a problem (coiled blanket wire too fragile)

geoff

[mr bruess]

i need Dew Control for my telescopes!!!

[RAJAH235]

Hi Geoff....
Bit iffy using nichrome but it can be done.....
The way I made the "termination", was to strip the outer 1/2" to 3/4" of insulation off the electric blanket heater. (EBH)
Strip about 6" of PMG/Telecom/Telstra single core wire.
Carefully wrap/coil 5 or 6 turns, reasonably tightly near the end of the EBH insulation. (Leave about 3 or 4 mm of insulation showing.)
Again....Carefully twist (about 5 turns) both the PMG wire & the EBH wire together. (Up the EBH wire.)
(The nichrome wire will want to unravel & don't worry about the high temp rayon/centre stuff, as it will melt anyway.)
Bend the PMG wire, (just at the end of the EBH + a smidge), 180 Degs & twist/wrap in the opposite direction back down towards the insulation, about 5 times.
Carefully twist a couple of turns in the opposite direction over the first "coils" on the end. (Don't need many here.)
Dip in solder flux (Tinsolflo is great) & apply a heap of solder to the wires....VERY QUICKLY. Be careful not to melt the outer EBH insulation....too much.
You'll get enough of a connection to be effective.
I use a 2 way terminal strip to terminate the heater & the supply (naturally) goes into the other side of the strip.
You can either screw or glue the terminal strip wherever you need.

Not the best looking electrical connection but suitable for this low Voltage/Current application.

[ballaratdragons (Ken)]

I don't have any problem using Nichrome for all my heater straps.

I just make a small loop at each end, then feed the electric wire through it 3 or 4 times, twist, and solder it.
Pretty much the way Laurie just explained it with the EBH wire.