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  #1  
Old 07-07-2010, 06:34 AM
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iceman (Mike)
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Article: Dew Heater Control and the Arduino

Bob Stephens (HikerBob) has written an article showing how to build a Dew Heater Control and the Arduino.

You can read the article at the IceInSpace Projects and Articles page, or directly by clicking on the link below:

Dew Heater Control and the Arduino

Thanks to Bob for writing the article.

If you'd like to submit an article or review to IceInSpace, please see the guidelines at Write for IceInSpace. We'd love to have your contributions.

Cheers and thanks.

Last edited by iceman; 07-07-2010 at 07:52 AM.
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Old 07-07-2010, 07:52 AM
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Article uploaded.
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Old 07-07-2010, 03:56 PM
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wasyoungonce (Brendan)
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Hi Bob....great work indeed. I was looking for inspiration and was recently reading your posts on this subject, you did last year.

I was looking at building (putting in the articles) a 4-6 channel PWM heater (I have designed & tested) and am now of the opinion that it is probably best done thru AVR (Arduino)...pretty much the same ideas you were at last year.

I sent Iceman my designs ( a week ago) for inclusion into the articles...maybe he didn't like it. I can see why now!

Excellent work you have done!
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  #4  
Old 07-07-2010, 04:14 PM
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Quote:
Originally Posted by wasyoungonce View Post
I sent Iceman my designs ( a week ago) for inclusion into the articles...maybe he didn't like it. I can see why now!
I don't recall receiving anything? Did I reply?

I've had a backlog of articles to upload for 3-5 weeks now so I may have missed it, sorry I'll check my emails.
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Old 07-07-2010, 04:32 PM
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wasyoungonce (Brendan)
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No problems PM sent...in the mean time I like Bobs AVR project very much indeed!

Now If I can get his AVR project and connect it to my output drive stage....
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  #6  
Old 07-07-2010, 04:37 PM
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Mike thanks for publishing that. Hopefully it will provide a useful starting place for others wanting a dew heater controller. The design should be able to be enhanced or dumbed down (I use a more basic version to provide multi channel dimming of Led lighting in my camper trailer).

I found an additional resource today which could be useful for anyone looking a using the idea's here but is able and willing to do some alterations. A Serial LCD controller based around an Atmel chip ( http://www.arduino.cc/cgi-bin/yabb2/...num=1260399444 ). I've not worked through what's involved yet but it could be useful.

wasyoungonce, thanks for your comments. Please feel free to float any improvements you can think of, I've been learning on the job with this. I'm very happy with the outcome but suspect that there will be a range of other options.

Bob
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Old 07-07-2010, 04:58 PM
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wasyoungonce (Brendan)
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Quote:
Originally Posted by hikerbob View Post
Mike thanks for publishing that. Hopefully it will provide a useful starting place for others wanting a dew heater controller. The design should be able to be enhanced or dumbed down (I use a more basic version to provide multi channel dimming of Led lighting in my camper trailer).

I found an additional resource today which could be useful for anyone looking a using the idea's here but is able and willing to do some alterations. A Serial LCD controller based around an Atmel chip ( http://www.arduino.cc/cgi-bin/yabb2/...num=1260399444 ). I've not worked through what's involved yet but it could be useful.

wasyoungonce, thanks for your comments. Please feel free to float any improvements you can think of, I've been learning on the job with this. I'm very happy with the outcome but suspect that there will be a range of other options.

Bob

Excellent stuff Bob. The only thing I'd look at is maybe higher pwr Fets. I used IRF4095 "p" mosfets, $1.44 ea, capable, ...well in my design ...I've run at 4.8 amps per channel but recommend 3A per channel (with a simple Heatsink). I mean who would need more than 3A per channel I ask?
But that would mean a complete re-work and don't I know it...you have to settle on a design and stop changing it at some stage!

I am trying to work out the STA508A ATM...just a little confused by it. Its a H bridge driver?

But using an Arduino. Yep that's the ticket. Great work putting it on eagle PCB. I did as well.

Well done indeed!

edit:

the more I see of it the more I like!
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Old 07-07-2010, 05:13 PM
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I meant to say as well. After I pretty much finished my designs I ordered a Duemilanove kit (on it's way as we speak) as I was going to play with 6 channel PWM after re-reading your posts from last year.


Sigh...beaten to the punch!
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  #9  
Old 07-07-2010, 06:18 PM
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wasyoungonce, I've been pondering a rework of the design to use individual fets just because the STA509A is getting hard to get.

The STA509A made a lot of sense on veroboard, not so much on a made up PCB. The STA509A is just 4 Fets with the source's already joined together which works well for the way I'm using them (and trying to do the switching between the 12V supply and the heaters looked difficult).
I won't be embarking on those mod's at the moment as I'm hoping that discussion will attract some feedback on power stage filtering, it's not been a bother to me but for those doing serious photographic work it may be an issue.

If it helps the amperage of dew-not heaters is listed on their website http://www.dew-not.com/specifications.htm I don't know what other straps draw.

Bob
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Old 07-07-2010, 06:21 PM
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I've just spotted the typo which identified the the fet array as STA508A rather than STA509A - sorry about that.
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  #11  
Old 07-07-2010, 07:23 PM
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Yes I am pretty much facing a wall with power filtering. Problem is switching Hight current effects everything attached to that line....well it does on my power supply. If I had 2 ccts at 3A and another 2 and .5A...a heap of switching inrush!

I have some high current chokes from jaycar I was going to put in line & fiddle...some day!

Iceman is going to put my ccts on so you can see where I'm at, unless you want me to send you my eagle files now?

Another issue is FET on rds. I pretty much faced pdip (package power dissipation) problems when trying many FETs with .117 milli ohms rds (or so) at 3.5A. Each TO220 FET package can dissipate around 2.5W (Max) and rds on rises with I draw & pdip case increase.

So I turned to very low on rds fets....020milli ohms (IRF4905)! My ccts were designed with these low rds FETs..less pdip issues. But ATM but I am greedily eyeing some new generation automotive intelligent power switch FETs that have I fold-back... like the IR1334 or IR3316. They are designed to run from 12V and have current fold back by using a resistor and/or even monitoring with something like an AVR.

I looked up commercial dew heaters & settled on a 3A per stage max output (with a little head room). Any more is for the big boys!

But I got to say I love your work.
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  #12  
Old 08-07-2010, 08:57 AM
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Thanks Bob! I need a little project in my life, and although I build my own PWM dew controllers already I'd like to investigate this one. Looks very interesting. I'll start investigating parts today.
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  #13  
Old 09-07-2010, 04:18 AM
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Thanks for posting and taking the time.

Minor point - the links in the article to the Arduino.cc website seem to be duds or not quite correct. I didn't check the others, but thought you might like to know.
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  #14  
Old 09-07-2010, 07:33 AM
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Troy thanks, I'd not rechecked links recently.

The link to the Arduino hardware page is http://arduino.cc/en/Main/Hardware

That lists all the official variants, there are a variety of unofficial ones as well such as the Sanguino, Freedunio etc.

Bob
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  #15  
Old 09-07-2010, 07:44 AM
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PCB variant

I'd not completed a PCB version when I originally submitted the article and somehow in the revision process the photo of that got missed.
Attached Thumbnails
Click for full-size image (B_013.jpg)
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  #16  
Old 09-07-2010, 12:19 PM
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I received some LCD displays from Satistronics today. The backlight does not appear to be working on any of them. I need to do some more investigation and I've emailed them to advise of the problem and to seek advice.

They appear to be identical to a number of display's I already had which don't have that problem (using the same dew controller and Serial LCD backpack).

I'd suggest anyone thinking of ordering them hold off until I see what their response is.

I also got some headers and pin strips from them which I use to connect the LCD, arduino and serial LCD driver to the board and they are excellent value compared to what I pay locally.
It should be a long time before I have to buy either again.
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  #17  
Old 14-07-2010, 09:28 PM
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I've discovered that the backlight connections are reversed on the LCD displays. I've still not received a response to my earlier message to them, I've sent on the additional information.

Bob
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  #18  
Old 06-05-2011, 04:20 AM
tjsteele (John)
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Adruino equiped dew heater controller

I was looking to build my own dew heater controller and found a couple different designs on the internet. One had a temperature controller and wanted to combine it with another pulse modulated project using a 555 timer. Then i found your post. This is exactly what i was looking for...

Has there been any modifications to this plan since it was posted (back in 2006) or has anyone else contributed to the design? For some reason i was expecting a very high cost but after looking at the parts, i find that the unit can be build for pretty cheap and will start looking into it very seriously. Can i still contact you guys for assistance if i get lost in the process (which i'm sure will happen - never built anything electronics in 20 years)?

I'm also new to astronomy so after trying my telescope a couple times last fall, i realized that this was needed badly so started looking right away. If i can build it, i would rather do that. Plus that's more fun to say that i built it then to say i bought it...

Thanks, T-J
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  #19  
Old 06-05-2011, 06:59 AM
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John are you on the right thread? My article only went up last year, not 2006.

Happy to help where I can. I need to get back to it very soon and finish another controller for a friend.

Bob
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Old 06-05-2011, 07:18 AM
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My bad. Been following too many links . But at least i got the right link for your build, and that's the project i need...

This adruino stuff is all new to me but tha's the way to go for sure. I studied electronic engineering back in 86 and i just wish i would have kept working in that even as a hobby but life took me in another direction. I'm sure i'm gonna pop a few neurons in this project but it's worth it...
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