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Xringer · 10-19-12, 09:55 PM

(Looks like lower middle would be a good place for a sensor).

Since there are air passageways in the HX fins, you could use two these detectors units, one on each side of the HX unit.
(using the LED on #1 and Photo-Transistor on #2).
I think the range in a dual device setup would be 3 to 4 inches.
Shoot the IR beam between the fins, to turn on the transistor, putting out near zero volts...
When ice filled the voids, less light passing would cause the voltage to increase towards +5.

The only problem with that idea, is really clear ice. (Optically clear).
Clear clean ice would likely pass a pretty good amount of IR light.

To work well, you would need a good ADAC to monitor the analog level.
And most likely a programmable controller to decide what voltage level = ice..

My Sanyo HX coils are stacked layers (dual coils, I think), so I'm not sure if light would make it from one side to the other..

~~~

Using the device normally (IR bounce mode), seems better IMHO, since the surface of clear ice has a substantial mirror effect.
Ever taken a flash picture, shooting through a car window?

I think IR bounce mode will work on white frost or clear ice, equally well.
It has the added advantage of near zero signal being reflected back to the photo-transistor.
Meaning it will be Off and the collector will be at +5V. However, if anything
reflective gets within 1/2" of the beam LED lens, it's going to bounce back and turn On the ~transistor.
If the transistor was half way on, (2.5V) or all the way on (0.2V),
either state means, start melting the ice..

Edit:
Wow, the price of 10 units just shot up by $8.. I paid $1.93 for 10 units.
http://www.ebay.com/itm/160742387966

Here's a better price..
http://www.ebay.com/itm/280760529898

10-19-12, 09:55 PM	#10
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	(Looks like lower middle would be a good place for a sensor). Since there are air passageways in the HX fins, you could use two these detectors units, one on each side of the HX unit. (using the LED on #1 and Photo-Transistor on #2). I think the range in a dual device setup would be 3 to 4 inches. Shoot the IR beam between the fins, to turn on the transistor, putting out near zero volts... When ice filled the voids, less light passing would cause the voltage to increase towards +5. The only problem with that idea, is really clear ice. (Optically clear). Clear clean ice would likely pass a pretty good amount of IR light. To work well, you would need a good ADAC to monitor the analog level. And most likely a programmable controller to decide what voltage level = ice.. My Sanyo HX coils are stacked layers (dual coils, I think), so I'm not sure if light would make it from one side to the other.. ~~~ Using the device normally (IR bounce mode), seems better IMHO, since the surface of clear ice has a substantial mirror effect. Ever taken a flash picture, shooting through a car window? I think IR bounce mode will work on white frost or clear ice, equally well. It has the added advantage of near zero signal being reflected back to the photo-transistor. Meaning it will be Off and the collector will be at +5V. However, if anything reflective gets within 1/2" of the beam LED lens, it's going to bounce back and turn On the ~transistor. If the transistor was half way on, (2.5V) or all the way on (0.2V), either state means, start melting the ice.. Edit: Wow, the price of 10 units just shot up by $8.. I paid $1.93 for 10 units. http://www.ebay.com/itm/160742387966 Here's a better price.. http://www.ebay.com/itm/280760529898 __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less.. Last edited by Xringer; 10-19-12 at 10:01 PM.. Reason: Price