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 Post subject: Ross's DIY Dew Heater
PostPosted: Fri Sep 28, 2012 7:07 am 
I must thank Ross for his instructions on producing a cost effective dew heater. I found the instructions easy to follow and even my basic soldering skills could cope with it.

I did however find that on e-bay there are "LED Light Dimmer Adjustable Bright Controller DC 12V 8A".

See link:http://www.ebay.co.uk/itm/280737152463?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

These come from China but are only £0.99 with £1.38 for postage and other people have received them within 2 weeks.

These seem to be a cheaper alternative to the Maplins "Panel Mounted Speed Regulator Module" Pt. No. RN41U.

Ross, with me not being an electronics guru maybe you could advise as to the suitability of these

regards,

Ian


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 Post subject: Re: Ross's DIY Dew Heater
PostPosted: Fri Sep 28, 2012 2:53 pm 
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Location: Bolton
imartin wrote:
These seem to be a cheaper alternative to the Maplins RN41U. Maybe you could advise as to the suitability of these


Well Ian, their specification of maximum 96W output will be more than enough for your heaters!
They must be worth a punt at that price.


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 Post subject: Re: Ross's DIY Dew Heater
PostPosted: Wed Dec 05, 2012 1:23 pm 
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Just to close the loop on this, I've just tested one of those LED dimmers, and it works fine. It's a very neat unit in a plastic enclosure, and the 4-way connector has screw-terminals so no soldering required. :-)
Mine took just a fortnight to arrive (with free postage from China).

A further word on the resistance wires used to make the heating elements:
The 28SWG constantan alloy (available from Maplin http://www.maplin.co.uk/28swg-resistance-wire-2196) has a resistance of 4.2 ohms per metre. This is good for large apertures (e.g. the front corrector-plate of SCTs) but you'd need a lot of turns to go around an eyepiece or camera lens. An alternative is nichrome wire (e.g. http://www.ebay.co.uk/itm/2-0-meter-NiChrome-Wire-32-swg-Resistance-Nickel-Chrom-/110505238061 which has a higher resistance, so shorter lengths can be used.


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