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Old 05-09-2020, 02:04 PM
RyanJones
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DIY dew heater controller

Hi all,

I decided to make myself a 3 channel dew heater controller. It features 3 PWM controllers with thermistors so as the temperature drops, the power to the dew heaters increases. The thermistors are mounted in a compartment at one end that has a fan blowing on them. Not quite as good as humidity sensors but still responsive to the air. Iíve used RCA plugs so that it conforms with industry standard heater straps too. Also features an LCD screen to set the wattage of each heater. Sadly I couldnít find one with red backlight but at least I can turn the backlight off once set. All in all Iím pretty happy with how it came up.

Cheers

Ryan
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Old 05-09-2020, 04:44 PM
redtail (Kenny)
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A write up would be nice.
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Old 10-09-2020, 03:49 PM
Pepper (Steve)
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Very nice. I’m building one myself. It’s off at the nerds for programming now.
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Old 10-09-2020, 04:48 PM
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Astronut07 (Ben)
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Ryan

Thatís a great looking setup!

I made a controller years ago using LED controller (PWM) unit but nowhere as sleek as yours

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Old 10-09-2020, 05:24 PM
Wilsil (Wilco)
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Would be interested to see how you did it and what parts you used.
Good job.
Does it work?
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Old 18-09-2020, 10:10 AM
gregmc (Greg)
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I like this project as it works on dew point and measures temp at strap which means only heat when needed

https://sourceforge.net/projects/ard...controllerpro/
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  #7  
Old 18-09-2020, 07:14 PM
RyanJones
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Thank you everyone .

Steve and greg. The Arduino version does look like a great option but I really wanted something I could do all by myself which certainly at this stage ruled out anything that needed programming. It certainly would have given me more options for control though. I did enjoy the challenge of trying to incorporate auto temp control into the system though.

Wilco, sounds like itís made the same way as Ben did. I bought 3 PMW motor/LED controller kits from Jaycar. I started by making a small dew strap using some resistors to use to test it. This required some calculations to create a strap that produced about 5W at full power (12v). I think overall resistance was somewhere around 25ohms. I built the PWM kits and wired up the Potentiometer remotely. I used the strap and tested it and it worked. Next was to integrate temperature control. I bought some thermistors that were about half the resistance of the potentiometers (47kohm). I wired them in between one leg of the potentiometer and the board so that the temperature dictated a percentage of the high/low timing of the pulse width. I mounted them to a prototype pcb and fitted into one end of the box with an exterior fan blowing onto them from outside the box. When it came to the screen, that wasnít my orginal intention. I actually wanted to have individual LED bar graphs for each channel. The problem was the IC to run the LEDs requires an analog voltage and the PWM output is just pulsing 12v so they didnít work. I looked into making a low-pass filter to smooth the voltage out but it stated to get to complicated for my little brain and stared to test my patience. In the end, I think Iím happier with the screen. I think it gives it more of a professional look. Iíve made a secondary heater to use with it already. See image below although this isnít the finished version and the finished one has a lot more resistors. Iíve tested that with it and it works perfectly so just quietly Iím quite a happy chappy. This weekend I hope to make my guide scope heater and then test it with 2 loads.

Thanks again for the interest and positive comments

Ryan
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Old 18-09-2020, 07:39 PM
jahnpahwa (JP)
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Very cool, Ryan!

I'd love to try something similar, but kid myself that i have no time. Good on you for making it happen 👍👍
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Old 18-09-2020, 08:03 PM
RyanJones
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Originally Posted by jahnpahwa View Post
Very cool, Ryan!

I'd love to try something similar, but kid myself that i have no time. Good on you for making it happen 👍👍
Thank you JP. This project started the first dewy night we had about 5 months ago and I think it will be just about ready for me not needing it until next year. Iíd love to have the time to do more of this stuff but I just donít in someways fortunately Iím one of a few people who has been able to work though Melbourneís lockdown.
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Old 19-09-2020, 08:04 AM
Pepper (Steve)
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Thanks for that write up. For me the programming is the biggest hurdle. Luckily my brother is more than capable being an I.t. Nerd.
He got it running and back to me the other day. Need a nice box like yours though.
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Old 19-09-2020, 09:33 AM
RyanJones
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Originally Posted by Pepper View Post
Thanks for that write up. For me the programming is the biggest hurdle. Luckily my brother is more than capable being an I.t. Nerd.
He got it running and back to me the other day. Need a nice box like yours though.
So did you use an Arduino module for yours ? The box I used was just a Jaycar hobby box with lots of cutting and drilling. Can you post a photo of your setup ? What dew heaters are you using ?
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Old 19-09-2020, 10:15 AM
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Nice box. Better than the dodgy one on mine
http://www.iceinspace.com.au/forum/s...d.php?t=144679
... Shameless plug
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Old 19-09-2020, 11:50 AM
RyanJones
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Nice box. Better than the dodgy one on mine
http://www.iceinspace.com.au/forum/s...d.php?t=144679
... Shameless plug
Nothing wrong with yours Chris and again yours is Arduino based which means yours has better control.
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Old 19-09-2020, 07:56 PM
Pepper (Steve)
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Using arduino uno with lcd plugged in on top.
I got the instructions on the jaycar website and after building it I got dht11 fault. This has been reported by many disappointed folk but apparently there is something funky with the code according to my brother.
Anyway, he got it working. Just need to draw up a box and get a few panel mount rca. Going to power it off a pc power supply along with a few other things.
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Old 19-09-2020, 09:32 PM
RyanJones
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Using arduino uno with lcd plugged in on top.
I got the instructions on the jaycar website and after building it I got dht11 fault. This has been reported by many disappointed folk but apparently there is something funky with the code according to my brother.
Anyway, he got it working. Just need to draw up a box and get a few panel mount rca. Going to power it off a pc power supply along with a few other things.
I have seen these while shopping for my parts at Jaycar. It looks like a pretty neat unit. Who knows, I may end up changing mine again down the track. Looking forward to seeing your finished product
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Old 20-09-2020, 03:11 PM
RyanJones
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Guidescope dew heater

Today I made a custom guidescope dew heater as part of my on going dew control project. Really quite simple. Itís a pair of egg rings with black card/plastic in between. I drilled 50 holes evenly spaced around and pushed through 25 510ohm resistors. Soldered them in parallel to create just over 20ohms total resistance. Soldered on a RCA plug and coated the inside and out with Velcro strips. It fits beatiifully as an interference fit around the end of the guide scope and with the controller creates up to 5W on full setting.
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Old 29-09-2020, 09:23 PM
RyanJones
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For anyone whoís been following:

I can happily say that it all works perfectly. I ran it for 6 hrs last night. The overall increase over a temperature drop of 5 Deg last night was a bit over 1 watt. And no dew formed on either the guide scope lens or the secondary mirror. It wasnít a bad night for dew but there was moisture on the OTA which in the past would have seen at least the guidescope start fogging up. More testing to come, maybe on a more dewy night but things look promising so far

Cheers

Ryan
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Old 30-09-2020, 03:23 PM
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Ryan

What's the box you used, and what's the internal dimensions (when you get a chance) ?

Chris
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Old 01-10-2020, 05:45 PM
RyanJones
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Ryan

What's the box you used, and what's the internal dimensions (when you get a chance) ?

Chris
Hi Chris,

Iíve attached a link to the box from Jaycar. The dimensions it gives are external so take off about 5mm for the internal and the corner posts for the screws come in about 8mm from the external corners of the box to the center of the screw hole. Allow another 3mm or so for the thickness of the post from center of the screw hole. It also has a very slight tapper to the bottom 2 mm max.

Hope that helps

Cheers

Ryan
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