Incandescent Bulb Modified to Become a Warmer at 40-45 Degrees Celsius

Shirley you jest.

The electric circuit is the easy part. The hard part is understanding thermodynamics so you can attempt to make this oven or toaster.

"Left to his own devices he couldn't build a toaster. He could just about make a sandwich and that was it."Mostly Harmless, Douglas Adams, 1992

A thermostat comes to mind but...How much air/water/food do you intend to "slow cook" with this device?

What's the problem? The circuit is too simple to bother detailing, as other posters have said. Just get hold of a thermostat and put it in the box or whatever along with the 40-watt bulb and the food. At a pinch you could use a heating system strap-on pipe thermostat, making sure the adjustment covers your range.

Of course heat losses must be less than 40 watt or it won't maintain the temperature.

Better ask how to modify an LED bulb - incandescent bulbs will soon be extinct.

I doubt this can be done at all with a 40W heater. The Easy Bake ovens that used an incandescent bulb for a heat source used a 100W bulb.

But presumably in an oven it would be rather warmer than 40-45°C?

True, but a light bulb heated Easy Bake oven could barely make just one high surface area cupcake at a time. As I said earlier the difficult part will be determining if 40W of heat is enough for this unspecified amount of food/water/air in an equally unspecified location.

Yes, I wouldn't disagree with that

If you have a good insulating enclosure such as a styrofoam cooler, 40 W should be enough. Obviously, the outside temperature needs to be lower than the desired inside temperature. A thermostat can be used, but it is an on-off device with a dead zone. If you need closer control of the temperature, the circuit below could be used (it will work on 120 volts AC).

http://www.electroschematics.com/5990/smart-heater-controller-circuit/

You are right. incandescent are almost extinct.

So my next crazy idea is to use alligator clips to pass electricity through activated bamboo charcoal, which I believe has a resisivity of 1.375 x 1 10^5ohm.

Does anyone know how to produce 45 watts of heat from this scrap.

Thank you all in advance.

Building a resistor from scratch will be just as much of a project as building a toaster from scratch. Just buy a properly sized power resistor and move on. Here is one of many 1000 ohm resistors rated to safely dissipate up to 100 W. Applying 220 VAC will produce 48.4 W. This one is also designed to be bolted to a chassis so you can easily distribute the heat.

My comment was not a total farce. LED bulbs, as efficient as they are, still produce a fair amount of heat. There has been a post floating around CR4 for quite some time about the 60 watt equivalent LED bulb and how dangerous it can be because it overheats the sockets of fixtures not meant for a LED bulb. A good porcelain fixture and some of the new 100 watt equivalent LED bulbs and you probably can get some usable heat. Maybe not enough for your application, but I bet we can still use these to keep pipes from freezing.

LEDs are 25-30% efficient, incandescents are 6-8% efficient.So for this application, incandecsnt lights are better as well as a lot cheaper.

Yes, but....the whole point of my posts is that incandescent bulbs are, at least in countries overly concerned about green house gasses, headed the way of the dinosaur. It would appear that we don't have to worry that we have no way to heat our pipe chases, crawl spaces, and make shift chicken coops in the future - LED bulbs still produce enough heat to replace an incandescent bulb - it will just take more of them. On the plus side - they won't burn out on that 10 below zero night and let your pipes freeze. We always had to check those incandescents every night to be sure they were still on.

In terms of cost and complexity heat strips are very long lasting and are quite low in cost compared to LED lighting in that they run on 120/240 volts directly and you can buy them is ratings in power in watts per foot to suite varied uses.

Incandescent bulbs win on cost now, as you say, but as they vanisdh from the market place, LED lights will not get as cheap because LED lights also need a lower voltage power supply to operate them.

Lamps and sockets are very low in cost for 120 or 240 volts, so they will be the winner for the next 4-5 years. After that old stocks of them will gradually ramp up in price and eventually few will buy them, since LED systems will be cheaper.

Paint the bulb black.

I expect that's tongue-in-cheek lyn, but in case it isn't, 40 watt is the input power and it all ends up in the box whatever colour you paint the bulb.

Only partly. I'm on a hand held and won't try to look at the emissivity of black paint vs the clear, unpainted glass.

But I don't think it makes any difference. 40 watt is 40 watt! I've heard people suggest painting radiators black to save money, and I've explained the same amount of fuel is burnt. It would just mean the circuit water is a little cooler to give the same heat output. I suppose that would give a slight improvement in boiler efficiency due to lower flue gas temperature, but that's not what they had in mind. Black rads might allow use of smaller rad area, but the difference would be small.

Well, I think it makes a little difference ( very little in this case, granted).

I say this because we painted our aluminum satellite electronics packages with black thermal paint to dissipate the heat built up inside the boxes. We would not have added the weight of the paint, if it did not have a specific purpose.

Part of my job was to determine the total weight of paints and adhesives we put into each module. I had a weight budget that I could not exceed.

Of course this was back in the days when the NSA only spied on our enemies.

That's exactly right. The surface (and hence the electronics) would be cooler with the black paint, for a given rate of heat production inside. But if the whole thing were enclosed in an outer box the equilibrium temperature in the outer box would be the same with or without the black paint. That's my take on it anyway.

My thoughts about this:

The filament of an incandescent light bulb is typically around 2200 degrees Kelvin. The glass surface doesn't get that hot due to the near vacuum inside the glass bulb, i.e, almost no conduction of the heat. There is also drop in intensity from the filament to the glass surface, the surface of the filament being much smaller than the glass surface. Since the glass is transparent to the majority of the black body spectrum of the filament, most of the energy passes right through.

Painting the glass bulb black would essentially make the paint the radiating surface, not the filament. The surface would then get powerfully hot.

Yes.

There is no convection inside a box in earth orbit, just as none inside the bulb. Little or no conduction inside the bulb either. So all the heat is radiated outward.

Everything in the electronic package did conduct heat and it was our job to get that to an outer radiating surface. Inside the package we relied moer on condition. Outside, we relied on radiation.

Another crazy idea. Why not simply break the glass so the heat reaches whatever requires heat but protected by a mesh?

If you mean the glass of the light bulb, that is a crazy idea. The glass seals in an inert gas, often nitrogen, to prevent the hot glowing filament from oxidizing.

That's why I can't understand ads for electric heaters claiming 'better efficiency'. Surely all of the input power ends up as heat anyway?

"Better efficiency" than what?

Exactly, they never qualify the statement.

Salesmanship. From the point of view of power into the appliance, an electric heater is 100% efficient, as you say, vs 80-90% for a gas or oil heater. But that conveniently ignores the fact that efficiency of electricity generation from heat input is about 40% tops.

Gas is less efficient but still considerably cheaper for heating.

That's right, but the electric heater salesmen don't tell you that! On a heat basis, cost of electric is 3-4 x gas, because of the conversion efficiency, 2nd law of thermodynamics and all that.

Incidentally, as you're in UK, I don't suppose you listened to Melvin Bragg on In our time (radio 4) the other week? He was discussing perpetual motion with a panel including physics professors. The 2nd law of thermodynamics came up and one of the profs said power output of a heat engine is less than the heat in "because of friction and heat losses". I thought that was lamentable from a physics prof, as the whole point of the 2nd law is that power out is less than heat in even without any friction or heat loss (some heat rejected to the lower temperature reservoir). That's my rant for the day!

I didn't hear it but I understand your consternation. Curiously, some years ago, completely out of the blue I was sent a book on the history of perpetual motion machines with a note asking me to review it. The publisher had no idea why they had sent it to me or how they got my address but said keep it anyway. An interesting book.

There are a large number of internet frauds based on heaters.

Heaters have a very low cost, even well made ones. So these heaters that make great efficiency claims, heat the room, high efficiency etc for $249.00 or some such high price are exploiting the poor and uneducated who supper under the false premise(caused by the advertising) that they can turn off their house furnace and rely on this heater.

These frauds persist, since they do not quality as frauds, since what they do say is technically correct, and exploits ignorance of people.

My stepsister is very happy with her $249 super heater and claims that it heats her whole living room better than anything. I tried to explain that anything that plugs into a regular wall socket(USA 15 amps) is not going to make more heat, no matter how special the design is. She thinks I'm silly and don't know what I'm talking about.

Weak minded girl who defends her bad decision?

We all know they are limited to 1500 watts max in USA/Canada, unless she has a 220 volt heater and plug.

There is an effect that can happen with radiant (infrared) heaters that explains this apparent extra warmth. The infrared energy directly heats the object they shine upon. So exposed skin and the temperature sensing nerves in this skin will be directly heated from this source. This can make a person feel that a room is warmer than it actually is. This effect is more prominent with a room with a high ceiling. The warmer air in a high ceiling room can be just above the space that a person is standing or sitting in.

I would leave the bulb clear. Spread the 40 W around, not concentrate it in one place. Keeping the heat in the bulb will shorten its lifetime.

I think it's moot anyway.

Besides we don't know the duty cycle in either case.

Google on "do it yourself food dehydrator", you'll find complete instructions for building the box and how to wire two bulbs in series as a heating source. NB- maximizing heat emission is not your goal, minimizing the radiant energy is, since you're trying to warm the food not cook it.

But a food dehydrator should also remove moisture vapor (vented fan) from the space. This is not what the OP asked for. They want the air, some probably moist food, and water to be maintained at about human body temperature. This sounds more like an incubator than a desiccator.

Oh, heaven help us. Have we just given a terrorist the last thing they need to make a bio-weapon production capability.

Remember that at 40-45degC, food will deteriorate rather more quickly than at the temperature to be found inside a domestic refrigerator.

What are you trying to accomplish.

An egg incubator?

Typically, you don't want to use a light bulb because the temperature swing is quite high when you're trying to make a heater out of a light bulb!

Sous vide cooking is usually done in a bath of hot water to maintain a constant temperature. The high specific heat of water makes it relatively easy to maintain a constant temperature.

https://en.wikipedia.org/wiki/Sous-vide

$40.

http://www.amazon.com/HotLogic-Mini-Personal-Portable-Oven/dp/B00EC7XJ28

....or you could just get a used warming tray from second hand store and build your own container....

It has to be a 40W warming tray.

Well, let's see: We have guesses ranging from an easy bake oven to a terrorist. All this based on incomplete information. This reminds me of an old joke:

"This anonymous poster walks into an engineering blog..." _{stop me if you have heard this one!}

Hmm. Both of those hyperbolic absurdities were mine. I wonder what that says.

To be accurate, Lyn is the only one who has suggested a modification to the light bulb. I agree with his analysis that the modification will probably not make much of a difference but it does answer the request for a modification of the light bulb.

Yellowstone will erupt and kill all life on earth before the average poster gives complete information here.

We must work with the tools at hand. Such as they are.

Well, AnonyPo1 has failed to stay connected, likely out of shear terror for having asked an absurd question to a collection of cynics and curmudgeons....

But in the spirit of "modifying a 40 watt incandescent bulb to maximise heat emission" (sp error is his), he could increase the voltage applied to it.

He gives us a 120V 40W incandescent bulb. P=V²/R, and R is fixed by the bulb design, so R = V²/P and at 120V, that means R = 360 ohms. So if V = 240V, then P = 160W, all of which would be heat.

The bulb may not last long, but that was not the question AnonyPo1 asked.

The #1 cynic/crumudgeon wonders where the 120 volts comes from.

Not from AP#1 near as I can tell. You may infer that, but it is not stated.

Also, painting it black qualifies as a modification to the bulb in my book.

Increasing the voltage supplied to it would would require furnishing a circuit, or instructions which seems to me to have been his original request.

It's like asking an engineer what time it is.

Where?

Ooops!

You're standing on the north pole. What time is it?

He never stated a voltage. I just picked 120V for my example. I picked it because that's what I live with. Had I bothered to ask AnonyPo#1 for his/her/its voltage, I would have been just adding to the pile of unknowns.

"It's like asking an engineer what time it is."

Yep, that's the joke I was thinking about! See, you have heard it before!

I guess if we can't get any useful information from the OPS these days, we might as well fill in the blanks on our own, and have fun with the subject!

Take a small refrigerator, size depends upon how big you want it, and modify it. At the bottom of the inside place a thermostat with the appropriate range, 104^oF to 113^oF or 40^oC to 45^oC, and make a "rain type cover" for the bulb to prevent liquids from dropping onto it. Some household thermostats may work for this range, if not find a cheap one. Wire the thermostat, the bulb, inside and a shut-off switch, with a fuse outside the box, all in series and connect this to a cord. Wire a plug onto it.

As the thermostat closes (not enough heat) current goes to the bulb, heat source, which heats the inside of the refrig. (heat box) When the temperature reaches the set point the thermostat opens and the bulb, heat source, shuts off. When you are done shut off the main switch and pull the plug out. If the bulb is too hot you can install a small chimney at the top out of sheet metal, 3" round stove duct is fine, with a damper for use as an adjustable vent/chimney. This is also used for something else. If the chamber is too cool replace the bulb with a higher wattage one or a lower one if too hot.

This can also be used, with a larger bulb as a food dehydrator or smoker. Such things as smoked fish, jerky, turkey, beef, rabbit, or anything else you can think of, can be dried in this. To smoke meat, put a small damper on the bottom of the door or the side of the chamber. This is a draft adjustment. Take out the light assembly and place an ash pan on the bottom of the chamber. Hang or place the meat on the upper shelves and start a very small fire (kindling type) out of hickory, oak, or whatever you want on the bottom of the chamber and let it smolder. When used for making smoked Whiting or Salmon the meat is delicious. For whiting dip the headless fish in salt water and smoke it as described above. When smoked to your preferences, peel the skin off and eat the meat. Salmon is even better!

All of this is a "Poor Man's Smoker". For $20, at the most, and a used non-working refrig you have a high class, but not beautiful, warmer, smoker and whatever you want it to do.

These are used on the east coast when the whiting and other fish are running. They are also used on Lake Ontario, at the Pulaski River, when the salmon are returning upstream to their spawning grounds. Smoked salmon roe, now that a delicious treat!

It is simple and cheap to make. With a little more effort you make this device that has several, if not more, uses. Certainly much cheaper than Cabelas!

Good Luck, Old Salt

That is about the correct temperature for making yogurt, or a little warm for egg incubation (depending on the bird).

You can buy wafer type thermostats for small egg incubators that are in the correct range. About $25 US

I'll start at the beginning instead of wandering all over this thread.

As has been said already, you gave us an incomplete description of your problem.

Here is some information you could supply that will enable us top help:

1. How big is your container?

2. What is the ambient temperature.

3. Does it need ventilation, or can it be sealed?

4. Does it need light, or can the light be absent? (Light can be damaging to some materials like food or medicines.

5. Is the application limited to 40 watts of power? AC? DC?

Offhand, without knowing enough, I'll toss you some comments. I would recommend a sealed airtight box with massive insulation. Theoretically, a perfectly insulated chamber will only need an infinitesimal amount of heat to raise the temperature very high. (see the alladin oven for an example) Instead of a light bulb, you could use a reptile heater, hot plate, etc. You'll definitely need a thermostat for this. Is the exac temperature critical? Johnson Controls have some pretty accurate digital thermostats.

Also, it is considered somewhat rude to post anonymously in some forums. It is free to create an account here.

Thank you all for your input. No intention to be rude. Just pressed the wrong button.Clumsy hand and mind.

The voltage is restricted to 220Volt. Container size is 8-12 liter thermal cooker. Have researched all over the web for reptile heater, food warmer, egg incubator,natto maker etc. The commercial natto maker is too deep. Bacteria need to breathe air. Others too high wattage, mostly 50 watt.

I am doing natto DIY.have gone through youtube already. There is a flaw in the info from the web. Hence I got innovative.

I considered a 7.5 watt hydor aquarium mini heater in the water in a 8 litre thermal cooker to keep space above water at 45deg Celsius. But review says it only keeps temp a few degrees above room temperature.

Your input as to which is the better solution appreciated.

Thank you all guys.

https://cookpad.com/us/recipes/155232-homemade-natto-using-a-yogurt-maker-japanese-food-anywhere-you-go

I would get 10 ea 1 qt yogurt makers, separate batches for better quality control....

http://www.ebay.com/itm/Salton-Yogurt-Maker-Machine-YM9-1-Quart-/262087790099?hash=item3d05a64e13

Do you see how deep the maker is? The rows below will suffocate.Bacteria need to breathe.

Does anyone know how to DIY a PTC heater 45 watts which can be attached to a wide surface area flat glass container housing maximum 2 rows of beans?

So you stack plates with shot glasses as separators....or make a nice circular rack with handle to mount the plates on.....I think you're making this much harder than it has to be....

I think you are the same guy, who wants to simulate the solar spectrum, or an extreme prepper

Food spoils faster at 40~45 deg C.

There is a sun beneath the Earth.

Tell me, what's your plan?

You can buy element heaters enclosed in a ceramic surround that have a two pin light connector just like a standard light bulb. Much more robust and durable than an incandescent bulb. Add a thermostat in series. To DIY this is far harder and more expensive than purchasing the correct item designed specifically for the task.

This appears to be the simplest solution for me. I can place a bowl of water to retain moister. Do you know any link leading me to 25 watt ceramic heaters? Placing 25 watt in an enclosed area like the thermos or oven with small ventilation holes will give me 45 deg celsius in 24 in hours.

Use one of those old coffee cup immersion heater coils. Place it in the cup/bowl/container to get the moist heat. They were last seen about 40-45 years ago. Throttle it back with IC circuitry or resistors. You may be in luck if there is a ready IC unit out there from some IC maker.

Luck, Old Salt

In Canada, sale of these immersion heaters, the type James Bond used in a movie, has been outlawed due to the way they start fires when not immersed after the liquid boils off.

It may be illegal but-----

With the voltage and current reduced an appreciable amount the risk of fire is negligible. In order to lower the temp to the desired lower temp, lower than it was originally made for, the power will be reduced significantly to maintain the much lower temperature. As others have discussed, less power less heat. Less power means less voltage and current entering the heater coil. If it was originally a 500 watt unit now operating at 110^oF (that's low enough that you won't burn yourself if you touch it) the voltage and current (power) are going to be too low to ignite anything except flammables with low flash points.

Good Luck, Old Salt

Follow this link and place the flexible heater(s) between two or more ceramic or porcelain tiles of 10" or 12" size.

These heaters are approximately 1/8 inch thick,and are flexible,and self adhesive.

They are commonly used in bill changers,etc. to keep the bills dry.

They work great,last a long time.Not had an element failure in over 10 years.

What could be easier?

You want it built and delivered?

http://www.grainger.com/product/TEMPCO-Flexible-Strip-Heater-WP104514/_/N-m2u?s_pp=false&picUrl=//static.grainger.com/rp/s/is/image/Grainger/6TFN1_AS01?$smthumb$#nav=%2Fproduct%2FTEMPCO-Flexible-Strip-Heater-WP104514%2F_%2FN-m2uZ1z0o0mqZ1z0nzfbZ1z0nru9%3FR%3D6THL3%26_%3D1444902790741%26picUrl%3D%252F%252Fstatic.grainger.com%252Frp%252Fs%252Fis%252Fimage%252FGrainger%252F6TFN1_AS01%253F%2524smthumb%2524%26s_pp%3Dfalse

Just check the web for "ceramic heater bulb". Most are about 60watts but if you are using a thermostat to switch the bulb on and off that will not matter. Alternatively if you have a local pet shop that sells reptiles they would likely stock these bulbs for heating reptile enclosures.

In fact, they have reptile heaters in glass tubes with a thermostat,

You can not beat the low cost of series lightbulbs, and a thermostat in series will run them as well.

Light bulbs are unreliable,and often need replacement.

In an unmonitored situation this can mean trouble.

I made a welding rod cabinet to keep my welding rods dry.

I used a self adhesive flexible strip heater,45 watt, and an old refrigerator.

I attached it between two pieces of 10 inch ceramic tile to disperse the heat and put it on the bottom rack.

Has been operating for 10+ years,no problems.

A line-voltage thermostat can be used to control switching.

Also a modified water heater element will work.You may have to tweak the internals to get what you want.

If temperature is critical,a number of cheap PID controllers are available on line.

Here's a link to some heat strips:

They may be available cheaper elsewhere,but this will start your search.

http://www.grainger.com/product/TEMPCO-Flexible-Strip-Heater-WP104514/_/N-m2u?s_pp=false&picUrl=//static.grainger.com/rp/s/is/image/Grainger/6TFN1_AS01?$smthumb$#nav=%2Fproduct%2FTEMPCO-Flexible-Strip-Heater-WP104514%2F_%2FN-m2uZ1z0o0mqZ1z0nzfbZ1z0nru9%3FR%3D6THL3%26_%3D1444902790741%26picUrl%3D%252F%252Fstatic.grainger.com%252Frp%252Fs%252Fis%252Fimage%252FGrainger%252F6TFN1_AS01%253F%2524smthumb%2524%26s_pp%3Dfalse

Good luck.

Here is a link to a cheap controller:

http://www.amazon.com/Inkbird-Universal-Temperature-Controller-Sensor/dp/B00HVA23CK

"I am open to modifying a 40 watt incandescent bulb to maximise heat emission."

A 40W incandescent bulb is ALREADY designed to maximize its heat emission. I'd need to do some research to get the exact numbers, but 90-95% of the energy you put into a 40W incandescent bulb is converted directly into heat.

People have already suggested using a thermostat to control the bulb's on/off cycle. You just need to determine if the 'diy warmer' has enough insulation to hold the heat in until it surpasses 45 deg C. If the warmer cannot hold the heat in, then the bulb will be on constantly, but the box will never reach the desired temperature.

There's two parts to it, as Jerry Seinfield stated when trying to get the car he reserved at the airport. "Taking the reservation is the easy part, anyone can take a reservation. But the important part is holding the reservation. If you don't hold the reservation, then taking the reservation is meaningless."

Start out with an experiment: build the box the way you think it should be built, then put the bulb in, using a simple light switch for control, and place a thermometer in the 'warming chamber.' See if the container design will reach 50 deg C under constant heating/illumination. If that works, then turn the bulb off and watch the thermometer, time how long it takes between the time the temperature hits 45C and 40C. The longer that time interval, the better the heat retention of the DIY warmer and the more efficient the final unit will be.

*does some math*

So 40-45C is 104-113F, that's the 'keep warm' setting on a modern oven. Depending on the size of the box and how fast it loses head, this could be done, but it may take more than one bulb.

Good luck with your Science Fair project, by the way.

A cheap and easy way to regulate the heat output of the bulb is to put it on a dimmer. This will reduce the heat output, but you'll have to monitor the internal temperature of the box to adjust it. Then keep an eye on it because of variables. Ambient temperature will affect it and as the thermal mass of the contents heat up, they will absorb heat less and the temp will rise. If the bulb is too hot or cold within the dimmer range, just use bulbs of a different wattage.

The setup I suggested isn't the final stage, it's just the 'sanity test.'

The final stage is what many before me have suggested: a thermostat to control the lamp's on/off cycle.

GA

This simple test will answer the question if 40W is enough energy for this incubator. The is a complication missing of this food preparation for dogsbestfriend making natto. This fermenting food will produce some amount of heat and out gas, too. It will likely take a few design iterations to get this exactly right. I'm not sure what gasses will be released but in case they are flammable it might be a good idea to only use solid state switches and brush less fans (if needed) in any part of this incubator that may contact these gasses.

Why Anonymous?

See #38.

Do try to keep up!

52 answers from a tease question?

Probably laughing his ass off.

There may be a flaw in your reasoning.

I'm sure the cats don't mind.

no, watts is E x I. With half the volts and half the current, each bulb make 25% of its rated output, more towards the red and IR. They light dimly, so 200 watts worth of bulbs make 50 watts worth of heat and a little light.

But bulbs only put out 6-7% as light at full rated volts anyway.

I am beginning to see your point.

Output is still 50 watts. But incandescent bulbs have short life. 1000 hours.

I still prefer ceramic. Much longer life. what about applying the dimmer theroy to ceramic heater instead. 50 watt ceramic bulb dimmed to 15 watts?

a 100 watt bulb used at 25% of wattage will last 20,000 hours

evaporation of metal is a function of the temperature to the 4th power, rendered in kelvin. Kinetic energy given to metals and some fly off.

at a dull red heat, W is far from it's boiling point of 5660 C = low vapor pressure

If 200 watt incandescent bulb used but only 20 % wattage used, what is its lifehours?

on the order of 20,000 hours.

Every 10 degree drop in temperature reduces evaporation by 50%.

Long lived bulbs are plotted on a log chart of voltage versus time.

So if it is rated at 120 volts, they run it at 250, 240, 230, 220, 210, 200, 190, 180, 170, 160, 150, 140, 130, 120. The burn 10 bulbs at each voltage and mark the average time on a log chart, and if you plot down to 60 volts you are about 20,000 hours. 50 volts even longer.

Actually, the resistance of a light bulb increases with temperature, so two bulbs in series would have somewhat less than twice the resistance of one connected to the same voltage.

http://hypertextbook.com/facts/2004/DeannaStewart.shtml

Yes, that is correct, and acts to prevent thermal runaway, which would happen if the resistance fell with higher temperature.

As for the idea of the series resistence being effective in making a safe low power heater, the main wish is to get longevity, and operating at 45% to 65% of full power will produce enough heat for the intended use and will have the longevity needed.

They would occupy 2x the space too.

But 100 watt bulbs are not energy saving. Need to use less energy too.

Thank you anyway.

wait . Can we use the dimmer theory to ceramic bulbs? 50watt ceramic bulb dimmed to 15 watt output?

you want heat. You will be using 50 watts. Use less = lower temp unless you insulate more. Add 6" of foam on all sides and you can do this with 2 15 watts bulbs = 7.5 watts of heat.

Use LEDs and it will not work, you want heat

Well, even LEDs put out heat, especially if they're 'screw-in replacement' bulbs, those have the AC/DC rectifier and power conditioner in the base, hence the cooling fins.

However, to put enough LED bulbs to get a good heat output, you would end up with a light output that would cause instant and permanent blindness to any cat that dared to stick its head in. NOT the desired result if you're trying to HELP the beasties.

Another way to live longer is to keep using our brain, be it drafting questions initially silly or brainstorming over the silly question.

This the another very simple solution. Thank you.