Wanted, Dew controller and Heater

leon · #1 11-03-2007, 08:34 PM

Hi All

I don't suppose anyone out there, would have a dew controller and a heater strap that would fit an instrument of about 5"

Not real fussed about the model type.

Please Pm me if something suitable comes to mind.

Leon

Thanks for the interest, but this item is not need anymore.

Leon

shredder · #2 11-03-2007, 09:58 PM

Hi Leon,

You can probably just buy one for under $80 from Bintel or Sirius or similar (I did for an 8") and then build the temp controller. Variable strength temp controller will cost about $30 in parts.... if you need the plans PM me and I will see if I still have them....

leon · #3 12-03-2007, 09:25 AM

Thanks Shredder, yep, you are probably right, it might be best to buy one from Bintel or the like, but I would certainly like to have a go at building the controller.

If you still have the plans I would certainly pay you something for them, I'm pretty handy, so building that shouldn't be to much of a problem, (I think)

Cheers Leon

shredder · #4 12-03-2007, 09:45 AM

Cheers Leon,

I will look for the plans, I am fairly sure I still have them. You are welcome to them, they were a ripoff from an internet controller plan from elsewhere anyway so I would not feel right in charging for them.

A small note or two... the controller I built was essentially the same as the basic Kendirc style controllers where you can vary the temperature over time etc. I made it so it simply fitted onto the power line for the basic dew zapper (say the orion ones) and so you had the choice to use it or not... I did notice when using it on an 8" SCT it did work fine, but as the dew zapper is essentially a long way from the corrector there is little to gain from adjusting the temp (because there is simply a lot of area and material to heat up). In short what I found was while the design was good and successful the actual need was not found to be there, either I had it on full or not at all (in general). But I guess this will depend on what you actually want it for.

As an aside the design also allowed you to add more heaters for other components such as unit finders, eyepeices etc.... actually worked quite well.

Anyway got to go find it now.

Cheers

Michael

shredder · #5 12-03-2007, 10:06 AM

Had a quick look and my plans arent on my work PC... must have moved them to home PC....

Had a quick look on the internet and found...

http://www.iceinspace.com.au/index.p...63,285,0,0,1,0

Low and behold its in our own back yard.....

While it isnt the one I used it is the same desing style, and pulse width modulation technique, where you vary the on/off timing cycle. It seems to also be in kit form so there isnt much of a problem building it (wish I knew at the time). The only thing to watch is that it can drive the correct current as dew zappers are current intensive (this can be easily handled via the resistors used if you know electronics).

An alternative design is....
http://home.comcast.net/~astrophoto/Articles/Dew.htm

Cheers

M

okiscopey (Mike) · #6 12-03-2007, 04:22 PM

Leon,

I just bought a 5-in dew heater strap for my ETX from Bintel .. it was $79. Seemed easier that dealing with resistors and nichrome wire.

As I have an existing Jaycar QM???? temperature measuring meter (which gives the temp difference between its two thermocouples) my idea was to just keep an eye in this and manually switch the heater on and off to keep the corrector a few degrees above ambient. The controller could come later if (a) the manual method didn’t work, and (b) if I won the lottery.

However, was in Jaycar recently and couldn’t stop myself buying the 12V Motor Speed Controller kit (KC-5225) for $23.95 (essentially a PWM device) and a UB3 box. I was in a rush so didn't get any other associated bits (cig socket, switch, LED).

Haven't tried the dew heater yet, and haven't built the kit, but will do soon.

The kit includes a tiny trimpot on the circuit board to vary the pulse width, so I imagine I'll be back at Jaycar to find a substitute variable potentiometer with knob to fit onto the box.

The kit looks fairly simple to make up and handles 10 amps (more than enough for the heater!). Dick Smith sells something similar I believe, but it may be of lower maximum amps.

The only reason I’m saying all this (much of which you probably already know) is to suggest it may be easier to buy this kit than get all the parts separately.

shredder · #7 12-03-2007, 04:29 PM

Have to agree with okiscopy.... since JayCar and Dick Smith actually sell the controller kits just buy one of them. BTW okiscopy if you want one that does what you are speaking of (ie checks a temp sensor and switches on / off) try that 2nd link (I posted before), it is a simple circuit that does what you are talking about.

Cheers

M

okiscopey (Mike) · #8 12-03-2007, 06:36 PM

Quote:

Originally Posted by shredder

... if you want one that does what you are speaking of (ie checks a temp sensor and switches on / off) try that 2nd link (I posted before), it is a simple circuit that does what you are talking about.

Thanks M, missed it first time round.

leon · #9 12-03-2007, 07:55 PM

Thank You for your assistance, you have given me plenty to work with, so I will have to go and do some researching.

Cheers Leon

erick (Eric) · #10 12-03-2007, 08:57 PM

Quote:

Originally Posted by okiscopey

......However, was in Jaycar recently and couldn’t stop myself buying the 12V Motor Speed Controller kit (KC-5225) for $23.95 (essentially a PWM device) and a UB3 box. I was in a rush so didn't get any other associated bits (cig socket, switch, LED).

The kit includes a tiny trimpot on the circuit board to vary the pulse width, so I imagine I'll be back at Jaycar to find a substitute variable potentiometer with knob to fit onto the box.....

Mike, I grabbed this kit during their 10% off everything sale, and have it sitting until I have time to make it up, but I spotted the same thing. Please let us know which pot you choose - I don't know whether the trimpot is linear or log - I was going to measure it ..... sometime. Thanks.

okiscopey (Mike) · #11 12-03-2007, 11:30 PM

Quote:

Originally Posted by erick

Mike, I grabbed this kit during their 10% off everything sale, and have it sitting until I have time to make it up, but I spotted the same thing. Please let us know which pot you choose - I don't know whether the trimpot is linear or log - I was going to measure it ..... sometime. Thanks.

Well, the destructions (probably an accurate term in my case) and the circuit diagram say it's 5k ohms. I assume from my limited knowledge that a linear pot will do as a replacement, as it's not a logarithmic application like audio. I made that mistake once in a sound set-up and all the volume came up in the last 10% of the knob twiddling.

So that's two kits awaiting construction ... I wonder how many more there are around the traps?!