Cat Heater

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jimandy
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Cat Heater

Post by jimandy » Tue Oct 11, 2005 7:45 pm

I’ll probably never do this project but here goes.<p>Start with my 24 yr old cat that craves warmth to soothe her aching joints. In the winter she lives in front of a gas heater but it worries us to leave it on, particular when we make an overnight jaunt to the mountain. Also, her sleeping quarters is our TV room in the finished basement and at night we retire to a 2nd floor bedroom so leaving the heater on gives us a worry.<p>In the winter we set the thermostat to lower the overall house temperature during our sleeping hours. Depending on the outside temperature the basement temp may drop 10 to 20 degrees depending upon the outside temperature. So I was thinking of suspending a 300 watt heat lamp (the red lens kind) so that she could sleep under it on her little cat pillow. <p>My project is to find a simple way to adjust the current through the lamp based on a temp sensor so that the colder the basement, the more heat output from the lamp. My simple mind sees a thermistor attached by some appropriate interface to a kluged up light dimmer to control the lamp intensity. <p>Besides the circuitry, the other task is calibrating it for her maximum comfort. This presents a problem since I can’t ask her if the settings are correct. The poor girl is stone deaf and doesn’t hear a word.
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Chris Smith
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Re: Cat Heater

Post by Chris Smith » Tue Oct 11, 2005 8:24 pm

I think they call them warming pads and electric blankets. They even have controllers. <p>I think you will find that a pre set blanket or pad is more than enough. <p>If not, put a roof on it. Also make the house with a warm side and a cool side so she can chose. <p>Cats will go where its nice, and if its too hot, she wont go there. <p>As to auto-adjustability, I don’t think you will need it with a roof and a variable choice from warm to cool.<p>Just make it warmer than the out side, and they will come. <p>With my puppies, I just made them a cardboard Condo, and point a 150 watt heat lamp at one side of the box from four feet away, and they adjust their sleeping position within the condo to suit their needs. <p>Light, dark, warm or cool. The box goes from cool to warm based on its large size and they like to sleep in the entrance when its too warm. <p>Light doesn’t bother them as they wake up every four hours to play.

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jollyrgr
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Re: Cat Heater

Post by jollyrgr » Wed Oct 12, 2005 3:30 pm

I don't know how much chewing a 24 year old cat might do. Or if the cat has bladder control issues. But they do make a heating pad specifically designed for pets. Go here for an example:
http://www.drsfostersmith.com/product/p ... CatId=1765<p>An electric blanket might work for her. But "medical" heating pad that your department/drug store sells might work as well. Place it in a pet box (something the cat can easily get in and out of without getting trapped) to help retain heat. Sneak the heating pad under the pillow (so the cat does not notice something different) and adjust the heat setting to one of the settings available. A heating pad is meant to be next to human skin and is usually a very safe item. You can sleep on it and it may get warm but never too hot to burn you; or the cat.<p>When you state gas heater, what kind are you referring to? Just curious as I live in a climate where a running furnace in winter is a must. (My furnace kicks on and off around the clock from about late October to April or May. The only difference being the temperature I have it set to; 62 when I'm not home, to 70 when I am.) What kind of heater is it that you don't want running all night?<p>Also, you might consider a ceramic electric space heater. Just watch to make sure stray cat fur does not collect around the fan and cause problems.
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jimandy
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Re: Cat Heater

Post by jimandy » Wed Oct 12, 2005 3:46 pm

Jolly, it's just a plain old 3 panel natural gas space heater. There's a nearby door that must be positioned to keep from getting hot from the heater and, since we have other cats, we worry that the young rowdy one might, in the night, jostle the door into dangerous proximity of the heater.<p>And, yes, I've used the heating pad idea with limited success. My theory on the hanging heat lamp is that it will give her more uniform heating since the pillow beneath her will keep her belly warm<p>Would it really be so hard to interface a thermistor with a light dimmer? Seems as a dimmer has a variable resistor (pot) that a thermister could simply be subsituted with just a few added parts for linearity. I would want full off on the lamp at an ambient upper temp of about 70f and full on at about 50f, with obvious tweaks if I find her whiskers curled the next morning.
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Robert Reed
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Re: Cat Heater

Post by Robert Reed » Wed Oct 12, 2005 5:08 pm

I like your idea of phase controlling a flood lamp for auto-heat. Most cheap lamp dimmers use a series RC circuit across the line for triac firing. Almost without fail the R will be composed of a small series resistor and pot of which the total res. will be 100 to 200K. the cap will probably be 0.1 MF. You can make up this R part with a thermistor of suitable value (may have to do some networking here to get the curve you want) The C part can be changed in value to accomodate the values of R you come up with. But dont go any higher than 0.1MF as you could exceed Ig max. You probably can go as low as 0.015 MF here. Any lower and you will run into triac trigger problems. In phase shifting conduction cycles, the first 30 degs. and the last 30 degs. have very little effect on the power output,as they will only comprise about 5% of the total power available. The important conduction periods will be between 30 degs and 150 degs.,so no need to go crazy trying to get a 180 deg. conduction cycle here. One problem will be that your remote Thermistor will be in the 120VAC potential range.<p>[ October 12, 2005: Message edited by: ROBERT REED ]</p>

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Re: Cat Heater

Post by Deal » Wed Oct 12, 2005 5:43 pm

Jimandy, congrats on guiding and sharing into 24th year. C. Smith had a good call on electric pet blankets. I am adverse to the insurance ripoff and am sensitive to possibilities where fluffy electric blankets intersect with pets and fire. I recommend a thermoelectric (there are other means of electric heating but I would chose to not combine pets with any form of heat elements) base as indirect warming to your cat's sleeping area. TE modules are low voltage, safe, and easily controlled. My animals have also lived very long lives, and I understand your concerns. I am not sure low voltage thermoelectrics negate issues of 60hz 120v electric destructive magnetics, but I would chose filtered low voltage of a thermoelectric sleepspace plate. Sure enough, TE modules are not as efficient as straight resistor electric but in heat mode are cateye close where small heatloads minimize the variable. Warm luck to you and your cat. <p>PS.. J Roger says heat settings 70/62 degrees. Come on J Roger, you have the ability to figue out intracies of a comfortable 60/52 household.

jimandy
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Re: Cat Heater

Post by jimandy » Wed Oct 12, 2005 5:47 pm

Thanks Robert. Now we're getting somewhere.<p>Getting that "curve" just right wll be the tricky part, I guess. Since this will be radiant heat, I can't actually use the air temp to do calibration (maybe I'm using the wrong term here). In other words the comfort of the cat will not have a direct relationship to air temp, but rather to the warmth imparted to her tawny brown fur from the radiated energy.<p>Hmmm. How does one measure radiant heat?
"if it's not another it's one thing."

Robert Reed
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Re: Cat Heater

Post by Robert Reed » Wed Oct 12, 2005 8:47 pm

Try a direct contact sensor on the surface its radiating on.

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philba
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Re: Cat Heater

Post by philba » Wed Oct 12, 2005 9:40 pm

it's kind nice that there hasn't been a single smart-alecky response to this...

Dean Huster
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Re: Cat Heater

Post by Dean Huster » Thu Oct 13, 2005 4:46 pm

I'd suggest inserting a probe in the appropriate place on the cat to sense its temperature. No sense warming the environment around the cat if the cat's doing fine. <p>Maybe I should bail out of this one right now so I don't take it any farther. Cats don't remain around me for more than 24 seconds, let alone 24 years, and it isn't the cat's decision unless it's suicidal.<p>One recipe I read says 35-40 minutes @ 350°F or until a toothpick comes out clean. Sounds good to me.<p>DANG!! There I go again!!<p>Hey, it's all in fun. :) <p>
Dean
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

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jwax
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Re: Cat Heater

Post by jwax » Thu Oct 13, 2005 4:50 pm

Cats? I love 'em!
Taste like chicken!
WA2RBA

jimandy
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Re: Cat Heater

Post by jimandy » Fri Oct 14, 2005 12:06 pm

My cat is terribly upset at the "roasted cats" remarks, but I will press on with the topic.<p>I found a fan speed control in the junk box, the kind you install in place of a wall switch (made by Lutron) Took it apart and it appears to have the triac, an inductor and cap and a pot that varies between abt 15ohm to 150K.<p>The question is can one of these be used as a dimmer? What is the basic difference in it and one for an incandescent light?<p>[ October 14, 2005: Message edited by: jimandy ]</p>
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Michael J
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Re: Cat Heater

Post by Michael J » Fri Oct 14, 2005 2:16 pm

The dimmer should work fine as long as the Max
Load rating for it is not exceeded(for light
dimmers here 240V 500W is common).<p>An Incandecent light and Heating element are both resistive loads.
If you have a dimmer for a fan it's probably even
better as a fan is an inductive load and they are
usually Zero Crossing switched.
I have a plain light dimmer, pot removed and
replaced with a tilt switch (Mercury type) which
is inside a Central Heating controller, this turns the lights on and off thermostatically inside my reptile enclosure. 15 years and only
replaced 1 triac.
The wire to this switch are at mains potential
so treat them as a live mains, insulation etc.

Robert Reed
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Re: Cat Heater

Post by Robert Reed » Fri Oct 14, 2005 4:55 pm

Jimandy<p>Your speed control sounds like a plain garden variety lamp dimmer. Fan contollers lead as simple a life as dimmers, since no closed loop feed back is needed. Like the light dimmer, you just set the control to the intensity/speed desired. Since each device runs at a non varying load it remains at that speed.If there are no chips or transistors in this circuit then it is as simple as they come, will work for either device within its ratings (almost all would have a minimum capacity of 500W).The inductor you see is part of an RFI filter (LC circuit) in series witth the load--these are usually toroid wound in the 100 micro henry range.

jimandy
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Re: Cat Heater

Post by jimandy » Fri Oct 14, 2005 5:32 pm

You guys are great! Reminds me of a cartoon I saw once when the harried executive was leaving for his intolerable job, as he left with briefcase in hand he turned to wife and said...<p>"Damn it Edith, you've given me courage to go on when all I wanted was the will to quit!"<p>but then I digress..<p>Anyway, I found a digital thermometer in wife's never-used kitchen accessories, the kind with a probe to stick in the cat, er uh, pot roast. The probe unplugs from the main unit and I put the ohmmeter on it and found that at room temp it hovers around 220 ohms. I then tested it with body heat (not the cat) and an ice cube but was rushed and have not found the ohmic range to cover 70 to 50 degrees. Will report on progress later.
"if it's not another it's one thing."

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