» Fixtures »Portable do-it-yourself warmer

DIY portable heating pad

Fixtures
Added 35 comments
Hello dear readers and the inhabitants of our site!
In this article, YouTube author Samodelki Vitmana will tell you how he made the simplest, compact hand warmer from highly accessible materials.

Materials
- Heat-shrink tubing
- Textolite sleeve

- A piece of plastic tube with a diameter of 3/4 inch

- Two bottlenecks

- Two caps

- Battery 18650
- Enamelled copper wire 0.25 mm
- Two small screws
- Two spring terminals for batteries

- microswitch

- Light-emitting diode.
Instruments, used by the author.
- glue gun
- Soldering iron, solder
- Technical hair dryer
- Pyrometer
- Screwdriver, drill
- File.

Manufacturing process.
To begin with, the author sets the switch. Drills a hole in the bottle cap and adjusts the size with a file.


Next, setting the switch makes a hole for the indicator (LED).


Everything connects and fixes on the cover with screws.



Then sequentially solder one spring with wires to the switch, and fix it with hot glue.



In one of the necks, makes a recess for the output of the wires, and screw it into the lid with a switch.



In a plastic tube, on the one hand, makes a similar groove. And on the other hand, symmetrically to the groove, makes a hole for the output of wires.




Leads the wires through the hole, installs the lid on the tube.



The same groove makes a file in the textolite sleeve.


Then it wraps on it a copper enameled wire with a diameter of 0.25 mm and a length of 6.5 meters. Puts a sleeve with a heating coil on the tube.




Now solders the ends of the wires and windings.


In the second neck also makes a groove for the wires, and puts it on the other side of the tube along with the second spring and solders the ends of the wires.





Now it checks in operation, it uses a 18650 battery as a power source.




The device heats up, the whole spiral. He puts on a heat shrink tube and warms it with a hairdryer.





The device is ready, the author installs the battery, and proceeds to testing in operation, and measures the temperature with a pyrometer before and after 5 minutes of operation. At the time of switching on, the temperature is 26.9, and after five minutes it reaches 44.2 ° C.





During operation, part of the heat is transferred to the hand, and the surface temperature of the heating pad decreases slightly, to 41.3 ° C.



As a result, the author obtained a compact and effective hand warmer, which will be indispensable in the cold.
It is interesting that the design will warm the battery itself, and this will allow it to work even in severe frost.

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Added 35 comments

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35 comments
+2
Reply To quote A complaint
Nothing is said about such a megavailable parameter in the cold as the operating time from a fully charged battery.
-2
Reply To quote A complaint
I understand that the site is about homemade products, but isn’t it better to buy this thing from the Chinese?
Author +2
Reply To quote A complaint
Wow, how many comments!
I have a second on the left. Kovea if that smoke
Author 0
Reply To quote A complaint
The jumper burns if briefly
+1
Reply To quote A complaint
Here is a suitable curler spool. From some kind of fiber (heat resistant). The diameter of the hole (for the battery) ~ 23mm. And on top of the wire (heating) is covered with material with a pile, which reduces cooling through the air. And when you squeeze in the palm of your hand, the pile is crushed and the thermal contact with the wire improves.
+1
Reply To quote A complaint
Not easier: you need to have a bunch of resistors of different ratings. Another thing is that having a resistor of several ohms, you can choose the current. But this will not be a complete imitation of a heating pad due to size, unless you take resistors 50 watts or more powerful. And for the product (not to simulate) in size suitable only PE-50, but you can’t put the 18650 in it. He will enter PEV-50, but there hard conclusions stick out.
0
Reply To quote A complaint
wrap a few meters of copper wire in this homemade product

It is easier to choose a resistor such as a sew.
0
Reply To quote A complaint
And if at all not theoretical, wrap several meters of copper wire in the same way as in this homemade product and apply current from an adjustable source. Measure the current at the temperature you like. Recalculate the length to the source planned for use.
+2
Reply To quote A complaint
Write the equation of the heat balance taking into account the external temperature not specified by you, and then everything is elementary: based on the input power, select the source and calculate the parameters of the heater.
The above design, provided that the battery is properly secured, protection against overdischarge is added and the circuit breaker is replaced, has the right to exist.
0
Reply To quote A complaint
At a fixed temperature there will be no maximum and minimum time

Is required not theoretical, and a practical, economical heating pad, powered by a Li-ion battery, temperature of about 40 degrees +3, we take into account that we warm our hands, and not the universe.
+1
Reply To quote A complaint
the portable heating pad should warm the maximum time from a specific source, the temperature of the heating pad is fixed.
At a fixed temperature there will be no maximum and minimum time. There will be one time under the condition of a given external temperature.
+1
Reply To quote A complaint
Quote: Nruter
The nichrome wire will reach the same temperature much faster and will go into steady-state operation.
Exactly the opposite: copper will heat up a little faster. The specific heat capacity of nichrome 450 J / (kg · K) at 25 ° C, copper - 385 J / (kg · K).
We consider the situation of bringing to the conductors of equal resistance from nichrome and copper equal battery power. All this power will be converted into heat, it has nowhere else to go, the rest of the effects due to their extreme meagerness can be neglected.
The nature of the conversion will differ slightly in the mechanisms and the time it takes to establish the heat balance, but still the heating will be the same in both cases, only in copper more evenly distributed over the surface.
0
Reply To quote A complaint
If the resistance of a nichrome wire is equal to the resistance of a copper wire,
I think this is not necessary, necessary economical warmer with a temperature of the order of 40 degrees.
+1
Reply To quote A complaint
Quote: Korolev
portable heater should heat the maximum time from a specific source

Here you need flies separately, cutlets separately :)
The source does not care what to spend energy on. If the resistance of a nichrome wire is equal to the resistance of a copper wire, then the source will work exactly the same for both resistances.
In the case of copper wire, energy will first be spent on heating the wire itself and reaching a certain temperature. The nichrome wire will reach the same temperature much faster and will go into steady-state operation. That is, nichrome will begin to give off heat faster than copper.
0
Reply To quote A complaint
nichrome radiation will give more than copper

The radiated heat will go away in shell, to the air, into the frame

copper will be warmer then due to thermal conductivity in frame and shell she will give more

I apologize, but with all my sincere respect for your professionalism, I have not been given a blunt understanding! smile
Let's try to come in from the other side: the portable heating pad should warm maximum time from a specific source, the temperature of the heating pad is fixed.
+1
Reply To quote A complaint
With the same power, copper and nichrome will act differently: they will give more than nichrome radiation than copper, so it will heat less. The radiated heat will go into the shell, into the air, into the frame and into adjacent turns. Since copper will be warmer, it will give more due to thermal conductivity in the frame and shell.
In total, that copper, that nichrome when summing up equal power will give the same heat, but in much different ways and a little bit in a different direction.
+1
Reply To quote A complaint
the heat that Nichrome radiates a little more than copper

warmer than nichrome copper

Honestly, I didn’t quite understand, but if it comes to portability, then it is also about economics (duration), I even got the idea to play with resistors like PEV, remember the green “boilers”, as a child, we made soldering irons from them!
+1
Reply To quote A complaint
That's it. In this product, the heater is covered with heat shrink. Therefore, the heat with which nichrome radiates a little more than copper will still remain in the space under the shell. Similarly, warmer copper than nichrome will give off heat in the same space.
0
Reply To quote A complaint
Watt - it is a watt ... "Electric" it, or "thermal" - no difference.

Another thing where this watt is spent
I completely agree with you, the conservation law seems to have not yet been repealed (or already, but I do not know? smile ) You can recall the lamps ... smile
+2
Reply To quote A complaint
I calculated from the source data from a copper wire ... R ~ 2.27ohm, I ~ 1.68A,
P ~ 6W, Q ~ 6J
The heater is more effective, of course, in one layer with a 0.4 mm manganin wire with a length of ~ 65 cm. At the same power.
There are such electric curlers. They are similarly made. They are of different diameters (for all sorts of curls). I measured R = 1.71kom (for d = 33mm) and R = 2.42kom (for d = 24mm). There, the wire in the form of nichrome 0.06 mm, wound in the groove of the insulator
+1
Reply To quote A complaint
here the battery will probably warm
Not sure, but for sure! In notebook, telephone, etc. Battery required temperature control!
0
Reply To quote A complaint
where this watt will be spent on - heating the conductor itself (different heat capacity), or the surrounding air ...
Well, I’m talking about the same thing, (taking into account heat conductivity and battery heating):
nichrome will release more heat
! smile
+1
Reply To quote A complaint
here the battery will probably warm itself) By the way, it will also work and how the heat accumulator works.

Can it just shorten the battery and bask from it?))
+1
Reply To quote A complaint
With equal energy costs, nichrome will release more heat into the surrounding space than copper.

And if the copper is already hot? )))))))
+2
Reply To quote A complaint
Maybe I'm wrong, but it seems to me that per watt of electric power, nichrome will generate more heat,

You are mistaken ... A watt - it is a watt ... "Electric" it, or "thermal" - it makes no difference ... Someone even once suggested that "energy does not appear and does not disappear ..." and I completely agree with this someone! ))))).
The efficiency of any electric heater is close to a hundred. Another thing where this watt is spent is on heating the conductor itself (different heat capacity), or the surrounding air ...
+2
Reply To quote A complaint
Comrades dear ...))))
All this is true, of course, only here ...
1. In this case, we are not considering a convector at all!))) We need to heat the body itself, and not the air.
2. At such meager amounts there will be a meager "error" between copper and nichrome ... But the "volume of a warm body" is just to our benefit ...
0
Reply To quote A complaint
You are not mistaken at all. At equal energy costs Nichrome will release more heat into the surrounding space than copper. Because the energy needed to heat a copper conductor will need more. This energy depends on the weight of the conductor, its heat capacity. And to get the same copper resistance, you need 100 times more.
+3
Reply To quote A complaint
Nichrome in this case will be much thinner, respectively, strength will be worse, especially considering baboutthe greater fragility of nichrome.
And where does this watt go? Another thing is that due to the fact that the radiative characteristics of nichrome and copper are different, the process of heat generation itself will not be exactly the same in time and space. With equal power, the air surrounding nichrome will be slightly warmer than the air around copper, but copper itself will be warmer than nichrome.
0
Reply To quote A complaint
copper is better than nichrome or another high-resistance conductor

Maybe I'm wrong, but it seems to me that per watt of electric power, nichrome will generate more heat, any spirals are now sold, distributing evenly is not a problem, although maybe I'm wrong.
+1
Reply To quote A complaint
In this case, copper is better than nichrome or another high-resistance conductor, because it can be evenly distributed overaboutthe largest area.
+4
Reply To quote A complaint
So same as nichrome ... Only it needs to be "thinner and more authentic" for the same heating .... And the maximum allowable temperature is lower (not for this case).
And I once (as a kid, in the early 80s) made a hand warmer. We were sent from school to "help our collective farms" to cut sugar beets. At the same time, hands mercilessly froze. And I wrapped a coil of copper “hair” and took a “flat battery” with me ... When my hands were completely “wooden”, I squeezed it in my hand and connected it. Enough for a couple of times to warm the batteries ...))))
The prototype was an anchor from the motor mentioned above here with two magnets on the sides. He also warmed up quite well ... But I did more powerful .... More precisely, not more powerful, but "bigger" - the temperature in my heating pad turned out to be lower, but the amount of heat was more ...
+3
Reply To quote A complaint
What is the difficulty?
+2
Reply To quote A complaint
About copper - I do not agree
Maybe I'm wrong, but it seems to me that copper does not cope with the conversion of electrical energy into thermal energy.
+1
Reply To quote A complaint
About discharge - of course, the battery will die at the most inopportune moment. About copper - I do not agree: the current will be 1.85 ... 1.33 A when the voltage changes within the acceptable limits of 4.2 ... 3 V. Here, using a switch designed for 100 mA in a two-ampere circuit is a bad decision. And also, saying about the LED, they did not say anything about the current-limiting resistor.
+4
Reply To quote A complaint
enameled copper wire with a diameter of 0.25 mm and a length of 6.5 meters
I think copper is not the best material for a heating coil. And I would like to know the battery life without a discharge controller! smile

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