The electric heater does not work. Electric heating pad: characteristics, application, description and reviews. Electric heating pad: description

The utility model relates both to meeting the vital needs of a person and to electrical engineering and can be used to protect household electric heaters from overheating in the event of a malfunction in these devices, in particular heating pads. The utility model solves the problem of ensuring the operational reliability of an electric heater by protecting the heating element from overheating with an increase in fire safety and electrical safety throughout the entire life of the electric heater. The technical result is achieved by the fact that in a heating pad containing a heating element enclosed in a flexible shell, the device protective shutdown electric heating pads from overheating in the form of an irreversible normally closed fuse connected in series with the heating element and an operating mode switch, a thyristor and a capacitor connected in parallel with the outputs of the heating element are introduced into the protective shutdown device, and the irreversible normally closed fuse is made in the form of a current fuse.

The utility model relates both to meeting the vital needs of a person and to electrical engineering and can be used to protect household electric heaters from overheating in the event of a malfunction in these devices, in particular heating pads.

A flexible electric heater is known (RF patent 2076462, IPC H05V 3/34, March 27, 1997), containing a cover, a heating element located inside the cover in the form of a zigzag curved tape and a thermal fuse. The disadvantage of this design is that when the heating element is crushed, uncontrolled heating occurs, which leads to damage to the device and ignition of the heater.

Closest to the claimed utility model is a household electric heater (RF patent 97624 MPK A61F / 00, 09/20/2010) containing a flexible shell with a heating element located in it, an operating mode switch and an irreversible normally closed fuse.

However, the disadvantage of this design is the insufficient electrical safety of the device, due to the fact that it does not protect the network from short circuits in the heating element and in the connecting wires, which is especially important for ensuring the durability of the device, since the insulation of the wires and the heating element located at high temperature by the end of its service life, it ages and collapses.

To prevent fire from misuse the following measures are applied: the timer limits the warm-up time; the overall power is reduced; thermal sensors and thermal relays are installed, thermal controllers are installed in the mode switches, fasteners are made to fix the electric heater on a person or on a bed. But as practice has shown, people leave electric heaters unattended, neglect the operating instructions.

The utility model solves the problem of ensuring the operational reliability of an electric heater by protecting the heating element from overheating with an increase in fire safety and electrical safety throughout the entire life of the electric heater.

The technical result is achieved by the fact that in a heating pad containing a heating element enclosed in a flexible shell, an overheat protection device in the form of an irreversible normally closed fuse connected in series with the heating element and an operating mode switch, a thyristor and a capacitor connected in parallel are introduced into the protection device. terminals of the heating element, and the irreversible normally closed fuse is made in the form of a current fuse.

Figure 1 shows general form heating pads;

figure 2 presents functional diagram heating pads;

figure 3 - design of the heating element.

heating pad contains a heating element 1, a device 2 for protective shutdown of an electric heating pad against overheating and a switch for 3 operating modes.

The heating element 1 is intended for heating the electric heating pad not higher than 60°C and is a thermal cable enclosed in a flexible sheath 4 containing a copper current-carrying core 5 coated with insulating layer 6 on top of which is wound a heating coil 7 of nichrome wire enclosed on top in elastic insulation 8. The heating element 1 is included in the temperature control circuit, and its temperature is maintained in the specified mode.

The protective device 2 of the heating pad is designed to protect the heating element from overheating.

Device 2 works only in combination with thermal cable 1. Thermal cable 1 is used as a sensor for exceeding the limit temperature, i.e. generates a signal for device 2, and device 2 is used as an actuator.

The protective shutdown device 2 contains an irreversible normally closed fuse 9, a thyristor 10 and a capacitor 11.

The irreversible normally closed fuse 9 is a current fuse having a rated value of the protective operation current approximately equal to the rated current through the heating element 1.

Fuse 9 is connected with one output to the power source through the switch 3 operating modes, the other to the first outputs of the heating element 1, thyristor 10 and capacitor 11.

The current irreversible fuse 9 is designed to break the power supply circuit of the heating element 1 when the current through it increases above the permissible value.

Thyristor 10 and capacitor 11 are connected in parallel with the terminals of the heating element 1.

Switch 3 operating modes of the heating pad is connected in series with current fuse 9.

Switch 3 switches the operating modes of the heating pad. In one of the modes U pit \u003d U network (where U pit is the supply voltage supplied to the heating element of the heating pad, U network is the voltage electrical network) the heating pad is operating at full power. In another mode, U pit \u003d 1 / 2U of the network (where U pit is the supply voltage supplied to the heating element of the heating pad, U network is the voltage of the electrical network), the mains voltage passes through diode 12, which does not pass the upper half-wave of the mains voltage, the heating pad works with 50 % power.

The heating pad works as follows.

During normal operation, the temperature of the heating element 1 does not exceed the set limit temperature.

When the heating pad overheats, the insulating layer 6 of the thermal cable 1 melts, as a result of which the heating coil 7 is connected to the copper current-carrying core 5. Further, the mains voltage pulse through the copper current-carrying core 5 is supplied to the protective shutdown device 2.

Since the heating coil 7 and the copper current-carrying conductor 5 are connected (in case of overheating), a mains voltage pulse will appear on the copper current-carrying conductor 5. The mains voltage pulse received by the device 2 affects the control electrode of the thyristor 10 and this leads to the tearing off of the thyristor 10, that is, the transition from a non-conductive state to a conductive one. During the transition to the conductive state of the thyristor 10, an additional current flows through it. As a result, the current through the irreversible fuse 9 will exceed the maximum allowable current through the fuse 9 and the latter will melt with current and break the power circuit of the heating element 1. To prevent the thyristor 10 from becoming conductive, when the supply voltage is applied, capacitor 11 is used.

Thus, the proposed utility model has the following advantages:

Overheating control is carried out over the entire area of ​​the heating pad;

The absence of contacts in an irreversible fuse through which a significant current of the heating element flows, and the use of a current fuse as an irreversible fuse significantly increases the durability of the device;

The introduction of a current fuse instead of a thermal one simplifies the device due to the absence of a heating element and the absence of thermal connection with the heating element, increases its reliability and durability by facilitating the operation of an irreversible fuse, which is located not in a compartment with a high temperature of 250-300 ° C, but in a place with normal room temperature 25-30°C.

The introduction of a current fuse simultaneously with thermal protection provides protection of the power supply network from short circuit (short circuit) in the heating element and in the connecting wires, which is especially important for ensuring the durability of the device, since the insulation of wires and the heating element at high temperatures ages by the end of its service life and is destroyed;

The absence of breaking contacts in the device, during the switching of which interference appears in the electrical network, in addition, the contacts have a very small service life.

A heating pad containing a heating element enclosed in a flexible shell, a protective cutout device for the heating pad against overheating in the form of an irreversible normally closed fuse connected in series with the heating element, and an operating mode switch, characterized in that a thyristor and a capacitor connected in parallel are introduced into the protective cutout device output of the heating element, and the irreversible normally closed fuse is made in the form of a current fuse.

Probably, many people still have such heating pads from Soviet times:

They had 3 position switches to adjust the temperature. In our age of electronics, it is a sin not to modernize such a thing, especially since it is quite simple. Here is a diagram of a thermostat designed for a fixed temperature of 36-37 ° C:

The basis of the circuit is a DS1821 temperature sensor operating in thermostat mode. At first, the circuit did not have a transistor, but practice has shown that such an inclusion of a temperature sensor is unacceptable. During operation, the voltage at pin 2 exceeded the power supply of the microcircuit due to a voltage drop at the control transition of the triac. This led to spontaneous reprogramming of the temperature sensor and disruption of its operation. I had to add a transistor (any low power one) and reprogram the thresholds TH0 and TH1.

It is most convenient to program the DS1821 to put it into thermostat mode and set the operation thresholds using a simple programmer. The sensor is placed directly inside the heating pad.

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 our hands warm.Therefore, I decided to hastily put together a mini heating pad especially for my precious hands.There are a lot of heating pads of this kind on the markets, but still I wanted to make my own.

On sale there are heating pads with a combustible mixture inside, these are long-term reserve hiking heaters based on the principle of catalytic combustion. There are also electric heaters 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 used as a heater for underfloor heating, they are also wrapped around water pipes so that the water in the latter does not freeze. well in general areas There are many uses for this heater.

The heater consists of two parts - a fibrous resistive material that actually heats up, and a heat-resistant flexible insulation.
Such heaters are powered by the mains, 10 meters of such a wire consumes about 160 watts when powered by a 220 volt mains. Exactly given material and decided to use in my heating pad.

Empirically, I selected the optimal power of the heating element; for this, a nichrome heater was used. Wrap the wire around aluminum frame power bank and picked up the length so that when powered by 12 and volts, the case would heat up to 50 degrees in a maximum of 20-30 seconds, as a result, it turned 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 desired length of the heater, but you need to take into account the fact that as it heats up, the resistance of the heater will increase, therefore the power will decrease, the length and resistance for my case are not so important, since everyone will calculate the heater individually depending on the supply voltage and heater length.

The heater will be powered by just one standard lithium can 18650 , but not directly, but through a boost converter, it is possible without it, but in order to get the desired power from 3.7 Volts, you need to shorten the wire length and connect several in parallel. In order to avoid a collective farm, I decided to use a converter, in which case the heater will be solid and will stretch along the entire length of the sleeve, thereby ensuring uniform heating.

In a heating pad, the battery must be protected, otherwise it may fail due to deep discharge.

Between the turns of the heater, he kept some distance, having received something like notches for the 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 input of the board and set 12 Volts at the output of the module by rotating the trimmer resistor. My case turned out to be too small and the converter board simply didn’t fit, but I didn’t want to change the case, in the end I decided to modify the inverter board with wire cutters, and that’s what happened.

The dimensions have decreased by two and a half times.

Let's take measurements of power and operating time. We supply a voltage of 3.7 volts to the input of the inverter, simulating a battery, we connect a heater and a wattmeter to the output of the inverter.

The consumption from the battery 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 with all this 2200mAh battery, it will last a little more than an hour continuous operation of the heating pad, and if this is not enough, you can take a 3400 mAh battery.

A heat-resistant adhesive tape is wound on the aluminum case of the power bank, in principle it is not needed, it was originally used to insulate 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 truncated converter board, I had to lengthen the case, since I completely forgot that at the beginning I planned to shove a USB charging system here.

The heater is turned on with a non-latching button.

The modern electric heater is the best device, which helps a person in the cold season to prevent a cold after hypothermia or relieve pain. A convenient and practical electrical appliance, which replaced rubber quickly cooling or catalytic ones, is a high-quality source of dry heat.

Frost and dank weather are not terrible if trouble-free warm heating pad which will warm the body and carry out a real physiotherapy procedure. In addition, it can be equipped with a vibration massager, which will help improve blood circulation in the feet, which has a beneficial effect on the entire human body, relieves pain, relieves spasms and speeds up metabolic processes.

Electric heating pad: description

This is a device for generating heat and constantly maintaining comfortable temperature with the help of electricity. Modern models not only convenient, but also safe. They are equipped with a triple protection mechanism that prevents the device from overheating and protects a person from electric shock. Blanket-shaped heating pad can be equipped with a timer automatic shutdown, which allows you not to get out of bed to unplug the cord from the outlet, but to fall asleep peacefully - the heating pad will turn itself off.

The device of modern heaters includes an internal heating element, an external removable cover made of heat-resistant fabric (fleece), a power cord with a plug and a thermostat. This design allows you to operate the device simply and comfortably. The cover is easy to remove and can be washed (machine washable on some models) to remove any stray dirt thanks to heating element heat is constantly maintained, and the thermostat controls the required degree of heating.

Types and forms

The current range of heating pads amazes even picky buyers. Every year more and more advanced novelties are released on the market for the use of electric heaters at home and in the country, in the car and while traveling. Today there are heating mats and warm pads even for pets!

In the production of heating pads, very durable materials- synthetic winterizer and high-tech polycotton (combination of cotton and polyester).

Electric heaters in pharmacies can be conditionally divided into the following models: for the body - small mats-mattresses, on which it is easy to lie and warm; universal appliances - flat pads small size applied to frozen parts of the body; specialized heating pads with electric heating, designed for specific parts of the body (legs, lower back, shoulder area, cervical region and spine).

They can have a special anatomical shape or be made in the form of boots, felt boots or slippers (an electric foot warmer), a heating vest, a belt or a roller. Pillows-hot pads are both in the form of a quadrangle, and in the form of a roller, orthopedic models serve to prevent cervical osteochondrosis.

Heating pads-mattresses can act as an alternative when turning off central heating. Models powered by the car's electrical network will come in handy on a long trip. Heating pads for chairs can be chosen both for home and for being in the car.

Bed linen and accessories (electric blankets and electric sheets) are as soft and pleasant to the body as regular ones, but are equipped with a power switch for convenient temperature control. Aromatic heating pads (Beurer Aroma) are additionally equipped with two fillers for aromatherapy sessions: for colds and for relaxation.

The use of heating devices

Heating pads are devices that are used to heat the body or separate zones for prevention or treatment.

An electric heating pad will help to obtain uniform dry heat with an adjustable level: in case of hypothermia (both the whole body and its individual parts); for muscle recovery after power loads; to increase tone and reduce excess stress in case of general malaise or after increased mental stress; in the fight against colds; to eliminate congestion in the blood supply internal organs and tissues, in the lymphatic system; for the care of bedridden patients (including postoperative); to combat diseases of the musculoskeletal system (diseases of the spine and joints, osteochondrosis, rheumatism); in the complex treatment of cystitis and other ailments that require dry heat.

Characteristics

Different types of electric heaters may also differ in characteristics: power - it is related to the heating rate of the device; quantity temperature conditions- this allows you to set the required operating temperature as comfortably as possible (in a heating pad for legs, for example, it should not exceed 60 degrees); automatic shutdown function - high-quality devices allow people to fall asleep without worrying about a burn or fire - the thermostat will turn off the device in time, preventing overheating; the presence of a vibrating massager (in electric heating pads for the legs) - this helps to work out the legs in various modes benefiting the entire body.

But warming and massaging the feet at the same time will not work - these two options are switched. The consumed voltage of electric heating pads does not exceed forty watts, so certified products are as safe as possible, pleasant to the touch and reliable.