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DIY Dew heater

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#1 Chris Westland

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Posted 04 March 2021 - 05:26 PM

Thought I'd post a quick share of my DIY dew heaters, since there have been discussions elsewhere about this.   SVbony sells various sized, nominally 5vdc, dew heaters for ~$15/ea.  They look nice, and are plastic on the inside for heat conduction, but fuzzy on the outside.  I bought 3 of these, and built dedicated 12vdc power modules for each, for ~$10 per box. 

 

The power modules include a hygrometer / thermometer (~$3/ea. on eBay for cigar humidors) to monitor the heater temperature and outside humidity (you can find the ambient temperature on your phone); and PWM modules (~$4/each on eBay) inside ABS plastic boxes (5 for $9 on Amazon).   The potentiometer on the PWM module changes the duty cycle to modulate temperature and save battery power, and they have a power light.  Your temperature at the scope should be just above the ambient temperature (or maybe a bit more if humidity is high).

 

That's it.  It's one box per dew heater, and if it breaks (which hasn't happened to me yet) just throw it out.

Attached Thumbnails

  • whole.jpg
  • box.jpg
  • therm.jpg

Edited by Chris Westland, 05 March 2021 - 12:39 PM.

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#2 dx_ron

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Posted 04 March 2021 - 05:50 PM

That's a neat idea. I hope the alligator clips are not a permanent part of the setup. Couple of questions: Did you clip off the usb connectors, or connect to the strap itself some other way? And, do you mind posting links to the specific parts you used?



#3 ngc7319_20

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Posted 04 March 2021 - 08:57 PM

Looks fantastic!  Thanks for posting!

 

Is there any issue running 12V into the heater straps designed for 5V?



#4 Chris Westland

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Posted 05 March 2021 - 12:41 PM

That's a neat idea. I hope the alligator clips are not a permanent part of the setup. Couple of questions: Did you clip off the usb connectors, or connect to the strap itself some other way? And, do you mind posting links to the specific parts you used?

Thanks for reminding me.  I've added links to Amazon/eBay for the parts.   

 

I did choose alligator clips (versus a proper battery connector) because I use 2 or more of these at once, and it just makes things easier to connect.  I'll see how it goes over time, and may ultimately switch to proper connectors.


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#5 Chris Westland

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Posted 05 March 2021 - 12:54 PM

Looks fantastic!  Thanks for posting!

 

Is there any issue running 12V into the heater straps designed for 5V?

Thank you.  No problems at all.  They are designed for a steady 5vdc, so with a steady 12vdc they would get pretty hot and burn up.  But the PWM controller is running them at a 10-40% duty cycle, so the power to them is pretty much the same, e.g.,  approximately P=E^2/R --> 5^2/R = .2*12^2/R

 

Oh, and I did clip off the USB connectors, and peeled back the insulation.  They also have a neat little switch with different power levels and terminated with USB connectors, which I didn't use.  


Edited by Chris Westland, 05 March 2021 - 12:58 PM.


#6 dx_ron

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Posted 05 March 2021 - 01:24 PM

If by "neat little switch" you mean the little wheel - I have never figured out how to get that thing set in a useful way. One reason I'm interested in your solution here.



#7 Chris Westland

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Posted 05 March 2021 - 06:46 PM

If by "neat little switch" you mean the little wheel - I have never figured out how to get that thing set in a useful way. One reason I'm interested in your solution here.

Here is what you find in the box (picture) for each of the dew heaters.  They're made for cameras and use a USB wall-wort plug.  The bag (BTW) is really nice, and holds the dew heater.

 

As far as positioning the PWM controller pot, I use the feedback from the thermometer on the box, and set it for a few degrees F. higher than ambient, which I get from my phone or from my Sky Quality Meter (pictured).

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  • sky.jpg


#8 dx_ron

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Posted 06 March 2021 - 08:40 AM

Ah. The Svbony straps I have came with a little plastic thumbwheel. I guess it gives continuous control, but "guess" is what you have to do.

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#9 Chris Westland

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Posted 06 March 2021 - 02:02 PM

Ah. The Svbony straps I have came with a little plastic thumbwheel. I guess it gives continuous control, but "guess" is what you have to do.

They must have changed them.   I'm not sure you guess any less with the attachment I have.  I like my system better, where you actually have a thermometer on the band.




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