Author Topic: Heat Tape Monitor/Controller to prevent pipes freezing  (Read 4221 times)

TomWS

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Heat Tape Monitor/Controller to prevent pipes freezing
« on: September 17, 2015, 07:55:03 AM »
I use a heat tape to keep our water meter from freezing in the winter. lining the entire plumbing stack near the meter with the heat tape and then wrapping the whole stack with insulation.  Good thing, too, last winter the crawlspace reached 18 degrees F!

I have a DS18B20 probe tied to the copper pipe coming off the water meter and, with the crawlspace temps at 18 degrees the copper pipe reached a temperature of 95 degrees F!  Good job insulating, but a bit of overkill on the amount of heat transferred!  The heat tape has a thermostat, but that only measures the ambient temp and turns on the heater if the temp falls below 40 F. 

Wanting better temperature control (at least not as extreme) and wanting to replace the WiFi monitor I was using (which proved to be unreliable), I've replaced the monitor and added temperature control with my latest Moteino project:   The Heat Tape Monitor/Controller (I'm not as clever at naming these things as others on the forum).

This is a relatively simple design using a Moteino, RFM69W, One Wire interface to the temp probe, and a Triac isolator/driver to control the Heat Tape power.  I also added a PIC12F1840 for hardware watchdog because I can't afford to have this unit hang up!

I designed this before Felix offered the Proto-PCB, but deciding at the last minute that I really wanted battery backup for monitoring purposes, I added the Proto-PCB with LiPo charger and resistor dividers on both VBat and 5V supplies.

It's all enclosed in a very convenient PolyCase box that has the AC connections built-in.

Attached are photos and the Eagle design files.

Enjoy,
Tom
« Last Edit: September 17, 2015, 11:29:43 AM by Felix »

gregcope

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Re: Heat Tape Monitor/Controller
« Reply #1 on: September 17, 2015, 10:29:36 AM »
I just LOL in the office at the name of this thing...

Nice project.

syrinxtech

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Re: Heat Tape Monitor/Controller to prevent pipes freezing
« Reply #2 on: December 10, 2015, 11:18:28 PM »
Neat project Tom.

We're using the same exact enclosure to house our ESP8266/relay to turn on and off the switch outlets via a Blynk app.  The enclosure does provide plenty of room to stuff in the goodies.

TomWS

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Re: Heat Tape Monitor/Controller to prevent pipes freezing
« Reply #3 on: December 11, 2015, 12:07:14 AM »
Thanks!  Yes, a very useful enclosure, and no wires!

It's currently keeping the water meter comfortably between 50 - 65 degrees F while the rest of the crawlspace is hovering around 40 degrees.

Tom

Felix

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Re: Heat Tape Monitor/Controller to prevent pipes freezing
« Reply #4 on: December 11, 2015, 09:02:57 AM »
As usual, nice project Tom!
Where can this case be sourced?
Any chance you could post a photo of the inside when the PCB is connected to the terminals?
The detail I am looking for is how the PCB is connected to mains, is it directly soldered to the 2 terminals?

syrinxtech

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Re: Heat Tape Monitor/Controller to prevent pipes freezing
« Reply #5 on: December 11, 2015, 10:07:17 AM »
Felix,

I got mine from:  http://www.polycase.com/ps-series

This is the family I use for indoor projects including my weather station with a 16x2 LCD:

http://www.polycase.com/jb-series


TomWS

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Re: Heat Tape Monitor/Controller to prevent pipes freezing
« Reply #6 on: December 11, 2015, 10:29:22 AM »
Felix,

I got mine from:  http://www.polycase.com/ps-series

This is the family I use for indoor projects including my weather station with a 16x2 LCD:

http://www.polycase.com/jb-series
Yes, exactly so.  Great source of enclosures in general.

Re Felix's question about connecting the mains to the PCB, yes, I have the edge slot routed so that the pads on the PCB surround the flat prongs on the supply plug and the PCB screws down to the existing bosses in the enclosure.  The eagle file is accurate (ie, no rework to the board) although I did add a LiPo so that the temperature monitor would still work when I lose power (Felix may note the use of his very useful I/O board for the LiPo charger).  Connection to the load side is via 18ga wire with fastons connecting to the L & N pins of the snap-in connector - I couldn't find a two pin connector that fit in the enclosure opening so the output connector ground pin, in my implementation, is floating...

The 3.5mm stereo jack is used to connect the THREE wires to the ONE wire sensor  :)

Sorry, no 'inside' photos... and I'm currently about 1100 miles from it.   ;)

Tom
PS: I can post the PIC source code if anyone is interested.
« Last Edit: December 11, 2015, 10:31:16 AM by TomWS »

syrinxtech

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Re: Heat Tape Monitor/Controller to prevent pipes freezing
« Reply #7 on: December 11, 2015, 01:21:23 PM »
Tom,

I noticed your mention of the PIC chip.  Not having any experience with that chip family I did a little research just to satisfy my curiosity.  If you don't mind I'd love to see the code.

Sergegsx

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Re: Heat Tape Monitor/Controller to prevent pipes freezing
« Reply #8 on: December 11, 2015, 01:26:26 PM »
Felix,

I got mine from:  http://www.polycase.com/ps-series

This is the family I use for indoor projects including my weather station with a 16x2 LCD:

http://www.polycase.com/jb-series

very nice boxes !! I have looked around and no luck finding anything similar in Spain or around Europe. If anyone knows where, please let me know. Thanks

Felix

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Re: Heat Tape Monitor/Controller to prevent pipes freezing
« Reply #9 on: December 11, 2015, 01:30:38 PM »
Sorry, no 'inside' photos... and I'm currently about 1100 miles from it.   ;)

PS: I can post the PIC source code if anyone is interested.

No problem, the explanation made a lot of sense.
Any sources/pcb files will probably be a good complement to what you posted already to make it a more complete project for those who'd want to replicate.
Thanks Tom.

TomWS

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Re: Heat Tape Monitor/Controller to prevent pipes freezing
« Reply #10 on: December 11, 2015, 02:57:26 PM »
Any sources/pcb files will probably be a good complement to what you posted already to make it a more complete project for those who'd want to replicate.
Thanks Tom.
PCB files were included in original posting. 

No source files since it would have to include my MASSIVE packet data structure code which I have no intention of supporting outside my own sites.  It's sort of intuitive though - looping reading one wire probe, see if temp is higher or lower than the two cutoff points, control gate to triac accordingly, post the temp at fixed intervals and don't forget to pulse the HW watchdog every time you post.

Attached is source for the PIC 'hardware' watchdog.

Tom

syrinxtech

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Re: Heat Tape Monitor/Controller to prevent pipes freezing
« Reply #11 on: December 11, 2015, 05:29:55 PM »
Thanks Tom.

I was noticing that SwitchDocLabs also sells a 2-port external WDT board:

http://www.switchdoc.com/dual-watchdog-timer/


Felix

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Re: Heat Tape Monitor/Controller to prevent pipes freezing
« Reply #12 on: December 12, 2015, 12:30:23 PM »
PCB files were included in original posting. 
Thanks Tom, I completely missed that link, doh.