D.I.Y. Dew Shields

[Mav359]

Hi guys

I was looking at the DewBusters website and the process of making the Dew Bands, looks good & with my awesome new soldering skills i am now wondering whats next?

Anyone had a go at this, are you happy with them etc etc?

Also if you have

he says to use 300 OHM resistors not the 300K/M, the searches i get back tend to be 300R, are these the same as 300?  i was looking at these......

http://uk.rs-online.com/web/p/product/131996/?grossPrice=Y&cm_mmc=UK|Shopping-_-Google+PLA-_-TE+Connectivity|Through+Hole+Fixed+Resistors-_-131996&kpid=&istCompanyId=f7e7b05b-2daf-4c0e-8825-3633baf8113b&istItemId=xwiwqrxwp&istBid=tzit&gclid=CO2L8Zn41LoCFfMdtAod7mYASg

I can integrate these into my new dew shield at both ends and there's the potential for the finderscope & even the telrad I could soon be in a dew free environment, no more hairdryers   

Cheers

[Mav359]

Also can you split a dew channel with one of these?

http://www.conrad-electronic.co.uk/ce/en/product/325099/

[leelee970]

300R is the same as 300 Ohms

300 ohms is 0.3 K ohms 

you could use resistive wire as well

and also easliy built a dew controller.

[leelee970]

here are some links

http://www.deepskywatch.com/Articles/newtonian-dew-heater.html

http://homepage.ntlworld.com/frederick.higginbottom/docs/astronomy/dew_heater_and_controller.pdf

http://www.wilmslowastro.com/tips/dewheater.htm

Lee

[RobertC]

To be quite honest, instead of buying the resistors separately it is better to buy them as a pack etc various resistor values over the long run if you are getting more into electronics.

etc http://www.rapidonline.com/Electronic-Components/E3-Series-480-piece-carbon-film-resistor-kit-74263

      http://www.rapidonline.com/Electronic-Components/E12-Series-610-piece-carbon-film-resistor-kit-74262

I salvage all my parts from broken electrical objects, right down to the components.

-Rob

[Gina]

"R" is often used to represent ohms where the omega character is a problem.  So yes,  300R means 300 ohms.  Also, to avoid confusion the decimal point is often replaced by "R" or "K" (kilohms) so 4.7 ohms becomes 4R7 (much clearer) and 4.7 kilohms, 4K7.

[leelee970]

I myself built the one using the 555 timer chip.

All i did was duplicate this a few times on one board to give me several independantly controllable outputs.

[Gina]

I made all my dew heaters from nichrome wire which is available in various sizes.  It's difficult to get as insulated wire so I use small heat shrink tubing with the wire threaded through (tricky/fun job ).  This will stand the heat generated in the wire.

[Mav359]

@Lee: My awesome new soldering skills aren't quite that awesome (yet)   besides i already have an astrozap dew controller with four outputs on it & a  bought strap.

I use one of the channels to power my LED feet on the tripod so that leaves me 3 channels. Initially of the top of my head i'm thinking of integrating a dew band at the top and bottom of the dew shield, one for the finder scope and one for the Telrad which is 4 straps in total hence the channel splitter question.

@Gina: The nichrome wire seems to be measured in SWG rather then AWG, same thing or not?

Cheers Guys

[leelee970]

if you split one output into two you'll reduce the current to each dewband, this may mean you'll get less heat from each.

[leelee970]

just looked at your temp obsy in your profile - hats off, well done

[leelee970]

swg - standard wire gauge

awg - american wire gauge

conversion links

http://www.urbanmaille.com/FAQRetrieve.aspx?ID=52710

[Mav359]

Cheers, its still standing and does the job although i think i'm out growing it to be honest

If i used less resistors at a greater distance apart would that pick up the drop in current (or is it the other way around, more resistors closer together)

Cheers

[leelee970]

I used 24SWG from RS

part number 714 1735

[Mav359]

Cheers for the conversion chart, all starting to make sense

[leelee970]

the distance between resistors is only for heat dissipation.

You’re testing my ohm’s law, lol

Resistance (ohms) = Volts (v) / current (I)

or V=I x R

or I = V/R

Your voltage is fixed as is the currant you want to draw from your controller.

[Gina]

One point with nichrome wire - it won't solder so use screw connections eg. terminal block.