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Winter came imperceptibly, I felt it when on the way to the store my hands were very cold. Of course I know about gloves, but they do not warm, but only keep the warmth of our hands. So I decided to whip up a mini heating pad especially for my precious hands. There are a lot of hot water bottles of this kind in the markets, but still he wanted to make his own.
On sale there are heating pads with a combustible mixture inside, these are camping heating pads with a long reserve on the principle of catalytic combustion.There are also electric heating pads with a built-in battery and a heating element.
A long time ago I bought several power banks with a metal case, and a heating pad was assembled on the basis of this case.
My heating pad will be electric.
On aliexpress, I bought an infrared heating element, which is used as a heater for a warm floor, they are also wrapped around water pipes so that the water in the latter does not freeze. Well, in general, there are a lot of areas of application for such a heater.
The heater consists of two parts - a fiber resistive material that is actually heated, and a heat-resistant flexible insulation.
Empirically, I selected the optimal power of the heating element; for this, a nichrome heater was used. I wound the wire on the aluminum frame of the power bank and selected the length so that when powered from 12 and volts, the case heats up to 50 degrees in a maximum of 20-30 seconds, as a result, I found out that this requires a heater with a power of about 6 watts.
Knowing some initial data and Ohm's law, you can easily calculate the required length of the heater, but you need to take into account the fact that as the heater heats up, the resistance of the heater will increase, therefore the power will decrease, the length and resistance for my case is not so important, since everyone will calculate the heater individually depending on supply voltage and heater length.
The heater will be powered by just one standard lithium can 18650 , but not directly, but through a step-up converter, it is possible without it, but in order to get the required power from 3.7 Volts, you need to shorten the length of the wire and connect several in parallel. To avoid the collective farm, I decided to use the converter, in this case the heater will be one-piece and will stretch along the entire length of the sleeve, thereby ensuring uniform heating.
In the heating pad, the battery must be protected, otherwise it may fail due to a deep discharge.
I kept some distance between the turns of the heater, having received something like grooves for fingers, so that the heating pad fits perfectly in the hand.
A cheap MT3608 scarf is ideal as a boost converter, we supply 3.7 Volts to the board input and turn the trimmer resistor at the output of the module to 12 Volts. My case turned out to be too small and the converter board simply did not fit, but did not want to change the case, in the end I decided to modify the inverter shawl with wire cutters, and that's what happened.
The size has decreased by two and a half times.
We will make measurements of power and operating time. We supply a voltage of 3.7 volts to the input of the inverter, simulating a battery, connect a heater and a wattmeter to the output of the inverter.
The battery consumption is slightly less than two amperes, of which about 100mA is consumed by the wattmeter itself, which is a little more than 7 watts at the input, and at the output we have 4.5-5 watts, the efficiency is about 70%. Naturally, without an inverter, there would be less losses. But even taking into account all this, a 2200mA / h battery will last for a little over an hour of continuous operation of the heating pad, and if this is not enough, you can take a 3400mA / h battery.
Heat-resistant adhesive tape is wound on the aluminum case of the power bank, in principle it is not needed, initially it was used for thermal insulation of the case. This is necessary so that the battery does not overheat, but later tests showed that most of the heat will be directly transferred to the hand, and the temperature inside the case is not critical.
Despite the cut-down converter board, I had to lengthen the case, since I completely forgot that at the beginning I was planning to shove the charging system here from the USB.
The heating pad is turned on with a button without fixing.
The button is located directly under the thumb, it is convenient, regardless of which hand you have a heating pad in.The button here is not easy to use, since the heating pad will mostly be in your pocket, then there is no guarantee that you will not leave it on, and there will be no such problems with the button, let go and everything turned off.
The charging circuit is based on TP4056 , nothing new. This fee also had to be reduced.
Well, now we turn on the heating pad and measure the temperature.
I think the result is excellent, if you hold the heating pad in your hand, some of the heat will be removed by the hand itself. and if it is too hot, then the temperature can be reduced by decreasing the output voltage of the inverter, it is not in vain that I made a hole for adjustment.
The coils of the heater can be glued with superglue or epoxy, or they can be sealed with thermal tape.
The case is not necessarily the same as mine; aluminum sleeves from some capacitors are excellent for these purposes.
By the way, it was possible to leave the motherboard of the power bank and recharge the phone if necessary, but this option was useless to me.
Finally, we glue the heating pad with aluminum self-adhesive film or aluminum tape.
It doesn't look good, but the heat is transferred more evenly.
The hot-water bottle has been tested more than once and coped with its tasks perfectly.
If the rear window defroster is out of order, the visibility is significantly reduced due to freezing and fogging. But do not panic - the "heating pad" can be repaired by yourself.
The heater is a grid of conductive material with a certain electrical resistance applied to the glass. Usually it is about a dozen horizontal threads, the ends of which near the body pillars are connected by two thicker vertical conductor threads.
First of all, damage to the threads can cause damage to the heater. If a horizontal line breaks, it alone fails, and damage to the vertical “bus” entails the failure of all the elements located behind it (in the direction from the electrical connector to the periphery). The damage is easy to identify visually, and the conduction of the broken conductor can be restored. Electric heater repair kits include a stencil that “draws” a conductive track, a brush and a tube of adhesive. With this kit, even an inexperienced motorist can repair the thermoelement.
If there is no visible damage to the conductive threads, you should look for a wiring fault. This requires a voltmeter or auto-tester. First of all, when the rear window heating is on, you need to check the presence and magnitude of the voltage on the wires supplying current to the terminals of the glass heater - it must be at least 11 V.
If everything is in order here, the next possible place for a contact failure is the heater's electrical connectors. They sometimes oxidize, which leads to an increase in the contact resistance. To identify this defect, you need to measure the voltage directly on the contact glued to the glass, without removing the “chips” of the supply wire from it. A voltage lower than that on the wire (less than 11 V) will confirm that the failure or poor performance of the heater is due to poor contact in the connector. In this case, it needs to be cleaned.
Finally, in the complete absence of voltage on the contacts near the glass and on the wires, you need to check the fuse “responsible” for this circuit.
But in the case when the fuse is working and its contacts are not oxidized, and the current does not flow to the glass anyway, the breakdown must be looked for in the switch or wiring. Such work is associated with the dismantling of the torpedo, and it is better to entrust it to professionals.
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As a result, simple heating devices will turn into a “VIP” device that has a real-time timer and temperature controls for separate control of the left and right halves of the heater or to turn off the heating completely.
There are many useful things in the world for comfortable living conditions for a person, one of them is the so-called "soft electric heater", or as it is usually called an electric blanket or an electric sheet.
In winter, I just can't imagine how I can do without it. When you dive into a warm bed. uhhh, a fairy tale….
I will say right away that for the sake of curiosity I did not disassemble my copy of the electric sheet. It is enough that all manufacturers as one claim that all these products have a quality guarantee, are safe and have the highest level of electrical insulation.
For these purposes, a device was made to control the heating of sleeping places on a microcontroller, which of course implies additional comfort.
The control program has the following properties:
Automatic switching on - turning off the heaters according to the real time clock, or manually according to the timer (operational setting for auto shutdown from 1 to 9 hours.).
Setting the heating temperature for each bed.
All data is displayed.
Display of a graphic thermometer on the screen, for room temperature from +10 ° С to + 35 ° С
Current hours, minutes, seconds, day of the week, day of the month, and year.
Room temperature display (main thermometer # 1)
Display of the temperature of warming up the sleeping place L (thermometer # 2)
Display of the temperature of warming up the sleeping place R (thermometer No. 3).
Functions; * The main thermometer No. 1 is a general control, giving commands for turning on the heating of sleeping places. ** Manual one-time switching on of heaters from 1 hour to 9 hours. *** Automatically turn on - turn off the heaters according to the daily timer. **** Thermostats No. 2,3 control the temperature of the heaters L and P.
Priorities. Control , carried out by means of three buttons.
Fuse: MK is clocked from the internal RS oscillator, for correct operation of the program, set to the internal clock frequency 8 MHz.
Since there are a great many different programmers, and I myself use this MK for the first time, for my own "fixing the material" I will give another example of what fuses look like read from the new ATmega168 with my programmer, and how they were installed later, it will not be difficult to make a comparison, and in the same way make the correct installation of the fuse on other programmers.
The circuit uses a switching power supply from a charging mobile phone, which very well suited this circuit, ! , small size, does not have a galvanic connection with the network, the output is stabilized 5 volts.
(Of course, I was lucky with power. But here 0.1A would be enough. But as they say, “they don’t look a gift horse in the mouth” :-))
Photo of the insides before installation in the case.
No. 8A (70x134x23), together with the second part, back cover No. 8U (70x134x5) Topic of section Homemade electronics, computer programs in category General issues ; Hello everyone! Not quite in the subject, but I ask for help. I bought a microlife heating pad the other day, it has 4 temperature settings.
Hello everyone! Not quite in the subject, but I ask for help. I recently bought a microlife heating pad, it has 4 temperature settings and an auto-timer for 90 minutes. Here's how to turn off the nafig timer, it's automatic and zadolbal to turn off, I need it to heat until you pull it out of the socket. I think this yellow thing is the timer. Or not?
If anyone helps him (the timer) to pull it out of the circuit, I will give him this timer!
The easiest way to make an electric heater is this one. To get started, prepare the following materials:
2 identical rectangular glasses with an area of about 25 cm 2 each (for example, measuring 4 * 6 cm);
a piece of aluminum foil, the width of which is no more than the width of the glass;
cable for connecting an electric heater (copper, two-core, with a plug);
paraffin candle;
epoxy adhesive;
sharp scissors;
pliers;
wooden block;
sealant;
several ear sticks;
clean cloth.
As you can see, materials for assembling a home-made electric heater are not at all in short supply, and most importantly, everything can be at hand. So, you can make a small electric heater with your own hands according to the following step-by-step instructions:
Using this technology, you can make an electric mini heater with your own hands. The maximum heating temperature will be about 40 o, which will be quite enough for local heating. However, for heating a room, such a homemade product will be, of course, not enough, so below we will provide more efficient options for homemade electric heaters.
Another original model of a homemade electric heater, which is suitable for local heating in a garage or room. All that is needed for the assembly is:
a can of coffee;
transformer 220/12 Volt;
diode bridge;
cooler;
nichrome wire;
textolite, with an area approximately the same as the diameter of a can;
drill with a thin drill;
soldering iron;
cord for connecting to the network;
push button switch.
This instruction is even simpler and you can make an electric heater from a can with your own hands in 1-2 hours. First, you need to remove the foil from the PCB and cut out the middle in it, as shown in the photo below:
After that, using a drill, you need to make holes diagonally. By the way, for this you can make a homemade mini drill according to our instructions. We fix the nichrome wire into the holes, after which we solder the wires.
We connect a transformer, a diode bridge, a cooler, a nichrome wire and a switch in one circuit.
We mount the fan in the jar using glue, and then attach the textolite as shown in the photo:
We put all the elements of a homemade electric heater in a jar, drill holes in the lid and check the device's performance!
If you want to make a more powerful device with a spiral, we recommend watching the video tutorial below:
VIDEO So we move on to more powerful electric heaters that you can easily make yourself at home. To make an infrared heater, we need the following materials:
2 sheets of plastic, area of each 1 m 2;
graphite powder, crushed to flour fraction;
epoxy adhesive;
two copper terminals;
cord with a plug for connecting to a 220 volt network.
So, you can make a do-it-yourself room infrared heater according to the following instructions:
Mix graphite with epoxy adhesive in a 1 to 1 ratio.
By the way, in order for the structure to be more durable, it is recommended to place the infrared heater in a wooden frame, which can also be made by hand. Do not forget to check the resistance of the device and calculate the power before connecting!
Another model of the device, which is recommended to be assembled for heating a garage or other outbuildings in the country. All you need is an old battery, tubular heater, oil and a plug. You will also need a welding machine, welding skills and some free time. The photo below shows one of the options for a homemade oil heater.
A tubular heater is installed at the bottom left, and an oil drain / fill plug at the top. Uncomplicated design of an electric heater, which will be enough to heat a small room.
The video below clearly shows how to make an oil heater with your own hands:
VIDEO Well, the last option for a home-made heater is a device that runs on 12 volts, which can be used to heat the interior of your own car. To assemble, you will need the following materials:
old power supply from a computer;
nichrome wire;
residues from floor ceramic tiles;
fasteners: bolts, corners, plates.
It is not so difficult to make an electric heater for your car yourself. The assembly process is recommended to be viewed at the master class in photo examples:
The disadvantage of such a heater is the increased risk of fire in the car, because nichrome wire is practically unprotected. In addition, you need to correctly calculate the power of the device so as not to damage the car's wiring.
That's all the ideas for assembling a homemade electric heater. As you can see, a simple electrical appliance can be easily made from various materials at hand, if you wish. If you liked the master classes, share the record with your friends so that they also know how to make a heater with their own hands for a house, garage or car!
It will be interesting to read:
VIDEO
VIDEO
Baking soda (sodium bicarbonate) readily reacts with acetic acid to form salt (sodium acetate) and weak carbon dioxide, which immediately dissociates into carbon dioxide and water. All components and reaction products are completely harmless, and the gas-rich mixture actively foams, making the pies more magnificent and forcing students to point fingers in surprise.
Sodium acetate is widely used not only as a food additive (E262), but also in the chemical industry - for dyeing fabrics, rubber vulcanization, etc. - and, of course, as part of warming "salt warmers". This substance melts at a temperature of about 58 ° C and easily dissolves in water, and if you then evaporate excess moisture from it and cool it, you can get a supersaturated solution that waits only for a slight "push" in order to instantly crystallize.
This exothermic process is accompanied by the release of a large amount of energy - from 264 to 289 kJ / kg. Unlike the production of sodium acetate, this is not a chemical reaction, but a physical process, a phase transition, and it is completely reversible. It is necessary to heat the mixture (for example, in a water bath), the acetate will again dissolve in the remaining water, and the "heating pad" can be reused.
Having briefly familiarized ourselves with the theory, let's move on to practical exercises. Of course, you can buy a “saline heating pad” at almost any pharmacy, and ready-made sodium acetate at the first suitable chemical store. But why? All the ingredients you need can be found in your own kitchen.
Take a suitable container (a saucepan will work fine) and add food vinegar. Keep in mind that as a result, the volume will decrease by about an order of magnitude - we had to prepare the acetate solution in several batches.
Add baking soda carefully, do not rush, letting each new portion react, otherwise you really have to get acquainted with the "chemical volcano". For every 500 ml of a 9% vinegar solution, we used 4-5 teaspoons of baking soda.
We have obtained an acetate solution, from which it remains to evaporate excess water. Place the saucepan on low heat and let the liquid simmer until fine crystals of acetate begin to appear on the sides. At the same time, the solution becomes yellowish and decreases in volume by almost 90% - this can take an hour or more.
While our solution was evaporating, we made an activator for the heating pad: we took out the base, a curved metal tape from the ruler bracelet, and cut out a circle from it, which, when pressed, bends in one direction or the other with a click. To prevent such a "button" from damaging the heating pad, it was tightened with electrical tape.
Video (click to play).
We poured the oversaturated acetate solution into a heating pad, putting our activator in it - but in principle, the reaction can be started without it. It is enough to throw in one of the crystals that remained on the walls of the dishes, and once spontaneous crystallization began with us simply from a sharp blow. The heat in such a heating pad [5] can last up to several hours, and for reuse it is enough to heat it in a water bath, again converting the acetate into a liquid form.
