kit to build dew heater controller???

[JonathanCR (Jonathan)]

Hi, this is my first post and my first question.

I have no knowledge in electronics so I am looking for some kind of a “kit” that I can buy to build a dew heater controller. I saw this article http://www.iceinspace.com.au/63-285-0-0-1-0.html but that kit is not longer available (I can’t find it anywhere) so maybe someone out there has another option. My power source is a 12V 7.5A sealed battery and I need 4 outputs (eyepieces, red dot view finder, green laser and maybe my secondary mirror in a near future)

Regards

[wasyoungonce (Brendan)]

While not a kit, either of these may be of interest to you.

[JonathanCR (Jonathan)]

Hi and thanks for your reply. I have been reading your posts about dew heating controllers and I find them and incredible source of knowledge in this area.
As I said before I know nothing about electronics and I tried to discuss the option of creating a dew heater controller with this kit in another forum but no one gave me a good reason for not using it.
There is one guy who created a dew heater controller with that kit, link here. He only added a 1k Pot and connected 4 outlets in parallel for what I can see. What do you think of that approach? I would like to run 4 heaters using my 12V 7.5A sealed battery. I don’t need a lot of power but I believe that is the purpose of the 1k pot, right?
thanks for your help.

[wasyoungonce (Brendan)]

This kit will work fine and has plenty of capacity.

Do what the gents on CN have done with this kit.

[hikerbob (Bob)]

Jonathan are you trying to learn electronics in the process?

If not and you really do know nothing about electronics the idea of building a kit could be a lot more hassle and risk than any cost savings are worth. If a kit does not work correctly it takes some knowledge to fault find. It also requires some equipment (soldering iron, solder, decent cutters, a multimeter etc).

I get the impression that some of the commercial unit's work fine if you don't want the bell's and whistles.

I've not used a commercial controller but do use commercial heater straps (and love them). I use the Dew-not straps http://www.dew-not.com/Order_Form.htm - their controller is only two channel so may not suit your needs.

Looking around I just found this one http://www.dewbuster.com/ but have no idea how good it is. Kendrick and Thousand Oaks seem to be popular as well.

If on the other hand you do want to learn some electronics it helps to have a meaningful project to work on.

Bob

[Tandum (Robin)]

I've built a few controllers from this kit and they work fine. No bells and whistles just variable voltage out for a reasonable price, in fact the case, plugs, sockets and ancillary bits to package the board cost more than the kit itself I note they now have a newer kit available, I haven't tried that one.

[mldee (Mike)]

You may also try ebay search for DC motor controllers. Plenty from Hong Kong and not too expensive. Work well.

[acropolite (Phil)]

The others are on the money, unless you're hell bent on building one, the thousand oaks 4 channel controller is excellent value, here in OZ Star Optics are selling them for $149.00, to build one of equivalent quality would probably cost upwards of $80. The thousand oaks also has an additional (fifth) fixed 12 volt output for additional items (e.g. your green laser) that don't need controlling.

I built a single channel one from scratch, cost probably between $20-30, I really couldn't be bothered making another controller.

[OICURMT]

It depends on what you are trying to achieve in the way of versatility...

If you want something EXTREMELY basic and NON-CONTROLLABLE that is EASY (as in EASY) to assemble... then http://www.skyandtelescope.com/howto/diy/3304231.html may be just what you need.

Includes a simple explanation of Ohm's law and a worded example of what it means in a practical sense.

PLEASE read the warning at the bottom... this dew heater is DC driven not AC.


OIC!

[JonathanCR (Jonathan)]

Originally Posted by hikerbob

Jonathan are you trying to learn electronics in the process?

Bob

Hi Bob, I guess I am, at least the basics. I was reading about the Arduino Uno board http://www.cutedigi.com/product_info...9851b68a8aa465 which seems really interesting to me because of my background in software development.

I wonder how difficult it is to connect a dew strap heater to that board? Is it necessary to incorporate something in the middle? Or is it just a matter of connecting the wires to the right PMW pin and the negative PIN (and the right sketch off course)?

[hikerbob (Bob)]

Jonathan the digital IO pins on the Arduino generally are rated at 40milliamps and heater straps between about .3 and 1.5 amps (or greater). The aruino works on 5volts, heater straps will typically be 12Volts. You will need some kind of switch in the middle and normally some resistors to protect the Arduino.

Have a browse at the material wasyoungonce and I have put up about the controllers we have built to look at idea's for output stages. There is also some good discussion around regarding considerations for the output stages (high side switching vs low side etc, RF suppression etc).

Cheers
Bob