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Dew Heater Power Supply - Visual Use Only


Alan White

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This may be in the wrong section, sorry MODs if this is tha case, please move as needed!

I need to use dew heater/s with my SW 100ED DS PRO as it dews up after a couple of hours use, and this is where I become unstuck as I have never used heaters to date.
One at the doublet and then one at the eyepiece, plan to just cover the finder as that at present is not a problem, but this may change.
Anyways, I use an AZ4 manual mount and no power either, I am the luddite me!

I need to power 2 -3 dew straps (small ones), I wish to hang the power on the AZ4 so the power and leads do not wrap around the mount 
as I wander around the sky in my free spirit observing sessions I am known to have.

Have bought the LED dimmers from China on FeeBay and plan a DIY controller, not sure on the heaters, may buy them, but you may point me to a good DIY solution/

So what power supply size do I need and do I make one, hence in DIY section or buy one, it needs to be compact or am I as usual a bit deluded??
Your help as always is appreciated, thanks, Alan

 

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This type of thing is about as compavt as you can get for a decent capacity - the only downside is you will need a lipo charger to recharge it.

http://www.ebay.co.uk/itm/Turnigy-5000mAh-3S-11-1V-Lipo-Battery-3-cell-for-Rc-Car-Plane-Helicopter-/231483134026?hash=item35e578504a:g:cyoAAOxyw3NTl3mw

Please DONT overcharge it, overdischarge it or puncture it !!!

 

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I have about 30 of them from little 1300 mah 2 cells to 6000mah 4 cells - and 6 chargers !!

Nothing to do with astronomy though - they are all for my model aircraft - electric power has largely taken over from glow and petrol power - less noise, clean, cheap.

I charge them and discharge them sensibly and I have never had a problem.

For my scope/mount I use 2 x 150ah leisure batteries - but they are 35kg each - not exactly portable !!

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Several things....

 

Whilst it's older, a Sealed lead acid battery might be a safer solution than a LIPO.   You can pick them up in a range of sizes.  A 17Ah battery should be more than enough power for you - once you have a working system, you could always measure the power requirement, and get an appropriate sized battery.  The 17Ah is the typical size that you get in car jump starters.  And they're fairly self contained, complete with charging circuits.   So plenty of options there.

 

As for the dew heaters.  If you want to decide on dew bands later on, add RCA sockets to your dimmers, so that you can connect the dew straps.  This is the standard connector that the astro world has settled on for dew bands.

 

To make the dew band, a simple way is to get a reel of NiChrome wire, and thread it through heat shrink.  You can wrap it with tape and insulation if you like too.    I made my own for my scope, and threaded the heat shrink wrapped wire through some copper brake pipe.  I bent the pipe, so that it sit's neatly in front of the main objectives of both my scopes.  To finish off, I painted with mat black spray paint.    The wiring, I run down the side of the scope to the control box.

 

There are several ways of making your dew bands... NiChrome as I said.   There is also the resister latter method.  Basically you buy a bunch of resisters, then solder the legs together so that the resister forms the rung of the ladder.  Next place power across the latter, (connect one leg to + and the other to -) and you have a dew band, again, wrap in duct tape insulation as required.

 

The resister method works better for eyepieces, the nichrome method works great for the main objectives.

 

Personally, I've found that I only need to stop the main objective dewing up.  For eye pieces, just keep them covered, and you can always place them in your pocket to clear any dew from them.

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Hi,

I had that problem myselfe earlier, too heavy and too big. Then I changed over to a 5 volt system and use an USB Powerbank.

Here is how I did it, se part 5 and 6. But please, don't try to build it if you not are an engineer and familer with electric constructions.

http://astrofriend.eu/astronomy/projects/project-heating-band/project-heating-band.html

There is a link to USB-Focus in part 5, write to him and explain what you need.

If you Google on Heaterband and 5 volt or USB you find them in the store.

/Lars

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I don't use heater strips here. But I'm a retired electrical guy.

If you can have an electrical cord to your viewing site, use a power supply (With sufficient amperage) to run your heaters.

Otherwise, I'd choose a lead acid deep cycle battery. I use an AGM type to run my kit outside. I charge it when it gets low, which is about once or so per week of heavy use. (Runs my mount, and CCD camera's cooling as a rule.) 4-5 evenings of use.

I find that the massive available power and long times between charging are very valuable to me. On the infrequent visits to field sites, this huge power source has offered me a long weekends running without fail. I do run a small (350 watt) inverter to run my Laptop when away, instead of heaters. And in a pinch, it can jump start my truck.

 

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Thank you all for your input, I feel more informed and confident.

I have decided to go for a 12 volt mains supply as the observing pad has a mains rcd outlet on it already, I can go battery if I go off site, but not done that yet.

As for heaters I have bought w &w ones from eBay, for quickness to be honest.

I will make something soon as my diy self is frustrated, perhaps a 12 volt power distribution board?

Again thank you all for taking the time to help me.

 

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SDC10751.JPGI have a 50ah banner deep cycle leisure battery which last for 4 days at least.

Its in a battery case with xlr sockets (changed not long after the pic above) for the main feeds to the dew heater controller. Correct fused outputs and a couple of meters for temperature  and current.

A bit over kill but it was left over when I saw the light and ditched the eq mount for visual. 

 

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I have one of these for when I'm out at a remote site, which I use to power the mount only.  It has a 2.5A output, with a standard 5.5mm outlet, so if you have dew heaters at 8W, then at 12V you're looking at 0.66A, so this would work fine, and is very light.

Power Supply

 

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XLR is a standard of connector.  It tends to be used in the audio industry, for audio applications.  The main advantage of it is that the plug and socket has a lock build in so that once connected, it's locked and won't fall out.

 

These are examples. of a 3 pin socket.   You'll only need 2 for power applications.  To release the plug, you'll have to press the tab marked "Push" on the socket.

http://uk.rs-online.com/web/p/products/0166462/?grossPrice=Y&cm_mmc=UK-PLA-_-google-_-PLA_UK_EN_Connectors-_-Audio_And_Video_Connectors&mkwid=sjYST2dZQ_dc|pcrid|88056666003|pkw||pmt||prd|0166462&gclid=Cj0KEQiA4JnCBRDQ5be3nKCPhpwBEiQAjwN1bvADnFoUGL_F6_syqejObFwAkqLpkBOSN_w-rV_rfXIaAsh48P8HAQ

 

http://uk.farnell.com/switchcraft/aaa3fz/socket-xlr-metal-3pole/dp/1192894?mckv=wxMfxzwG_dc|pcrid|78108395109|&gross_price=true&CATCI=pla-131305330869&CAAGID=20220702909&CMP=KNC-GUK-GEN-SHOPPING-SWITCHCRAFT&CAGPSPN=pla&gclid=Cj0KEQiA4JnCBRDQ5be3nKCPhpwBEiQAjwN1bqeTzPl-Jlr0sk5yf0s8rFSHu2BdLukGXTcbjZHYiSgaAoU-8P8HAQ&DM_PersistentCookieCreated=true&CAWELAID=120173390000012818

 

XLR plugs and sockets typically are 3 pin, but you can also get 5, 7, and more pins configurations.

3 pin is used for mono audio, one ground and two to carry the voice - phase inverted so that they signal can be recombined and the noise removed.

5 pin are used for stereo applications.

They can also be used for power applications and are capable of supporting several amps per pin - which makes them ideal for astronomy use.

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Beat me to it there.

I use them as cj says because they lock in more of an advantage if you're an imager or have a tracking eq mount as a pulled out plug can be frustating.

You can also get waterproof types from Speakon, more expensive but very good quality.

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  • 3 weeks later...

As an update.

I have bought an AGM Lucas battery 22ah for golf buggies, and stuck a 4 way cigar lighter unit on top with double sided tape.Small simple, better than a power tank and cost me £38.

Looks like what it is a battery with an outlet stuck on top, but who cares, I use it in the dark.

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1 hour ago, Alan White said:

As an update.

I have bought an AGM Lucas battery 22ah for golf buggies, and stuck a 4 way cigar lighter unit on top with double sided tape.Small simple, better than a power tank and cost me £38.

Looks like what it is a battery with an outlet stuck on top, but who cares, I use it in the dark.

Perfect Alan! I only have a couple of suggestions:

1. Get a good battery charger that specifies it has an AGM mode. More here to care for your new jewel. I love my AGM battery!

2. For ease in moving, I suggest a "Battery Box". It's merely a plastic box with a lid to keep your power source in. It's safe, it's tidy, and it has two handles. (I leave the strap off though.)

Mine also has room for the wiring and my 350 watt inverter I have to run my laptop. :wink: (Note to self: Next time get a 12 volt laptop. :hiding: )

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Thank you for that, I was still bothered about lack of carry box, so will take your point and advice.

Charger I have says it's for AGM motorcycles battery, but will check out other options to ensure I do not stuff the battery from poor charging.

Again thank you and Happy Christmas to you.

 

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  • 4 weeks later...

The wiring looks like it's good enough quality not to worry about short circuits and things like that.

Simply solution to the problem.

 

In time though, you might want to upgrade to a battery box.  With enough space in it to wrap the battery with insulation.  Batteries don't like cold weather - especially those crisp clear nights.  You'll loose quite a bit of power dew to cold weather.

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