Refrigerator with door opening sensor. Refrigerator with door open sensor Refrigerator open door unit wiring diagram
In modern household refrigerators, the door is fixed in the closed position using magnetic rubber. This, of course, is very convenient and the rubber gasket fits snugly, but the disadvantage is that the absence of any lock or latch leads to the fact that if the force is insufficient or excessive when closing, the door remains ajar.
And this is very dangerous not only for perishable products, but also for the refrigerator itself, because it is struggling to cool the entire kitchen, which, of course, it cannot do. The compressor overheats and deteriorates. Not to mention the electricity wastage.
The device described here is externally a sounding soap dish, which must be placed in the refrigerator on a shelf near the backlight of the refrigerator compartment.
If the refrigerator is working, then when you open its door, the backlight inside lights up. When the door is closed the lamp turns off.
The signaling device works like this: if the refrigerator door is left open for more than 5-6 seconds, an intermittent sound is heard, which will sound until the refrigerator is closed. The time of 5-6 seconds is not critical, it depends on the resistance of one resistor, and during adjustment it can be set to anything.
Alarm circuit
The circuit is built on two identical microcircuits of the 4001 type (K561LE5, K176LE5). A photorelay is built on the D1 chip, which determines by the illumination inside the refrigerating chamber whether it is open or not. In addition, a timer is made on one element of this microcircuit, which determines how much time must elapse from the moment the door is opened in order for the sound alarm to turn on.
The light sensor is a photoresistor FR1. Unfortunately, I do not know its brand and nominal parameters (at one time I dropped it from somewhere). But checking with a multimeter showed that in a closed refrigerator its resistance is about 500 kOhm, and in an open one it is about 8-20 kOhm (depending on the proximity to the lamp inside the refrigerator).
Photoresistor FR1 together with resistor R1 forms a voltage divider that depends on the level of illumination. When the door is closed, the voltage across it is near logic zero. When the door is open - about a logical unit.
On the logic elements D1.1 and D1.2, a Schmitt trigger is made, which is necessary in such cases. It provides clear switching thresholds on a signal from the photosensor.
Rice. 1. Schematic diagram of a homemade signaling device for refrigerator doors.
The timer is made on the logic element D1.3 and the circuit R4-C1. After a logical unit appears at the output of D1.2, it takes time for it to appear at the inputs of D1.3, which depends on the charging rate of C1 through R4, this time depends on the capacitance of C1 and the resistance of R4.
To create the effect of intermittent sound, two multivibrators were made on the D2 chip. The multivibrator on D2.1 and D2.2 generates pulses with a frequency of about 3 Hz to interrupt the operation of the audio multivibrator on D2.3 and D2.4, which generates pulses with a frequency of about 2 kHz. Element D1.4 serves as an output stage, to the output of which a piezoelectric sounder BF1 is connected.
When the refrigerator is closed, the voltage at the inputs D1.1 is equal to logic zero. The same voltage is at the output D1.2. Capacitance C1 is discharged and the output D1.3 is a logical unit. The multivibrators on D2 are blocked. No sound.
If the door is open, the output of D1.2 will be a logic one. Capacitor C1 starts charging through R4, and after 5-6 seconds the voltage across it reaches a logical unit. The output of D1.3 is zero.
The multivibrators of the D2 chip start and an intermittent sound is heard.
Installation and details
Powered by an imported analogue of the "Krona". In static mode, the current consumption is minimal, and the battery should last for a long time. BF1 - 7BB-20 piezoelectric sound emitter (round plate with wire contacts).
The assembly was carried out in a plastic soap dish without the use of a printed circuit board. Two CD4001 chips are glued to the bottom of the soap dish with Moment glue, so that the pins are up. Previously, the first conclusion is marked. Then the mounting is done in a volumetric way, using the microcircuit leads as mounting racks.
The frequency of sound interruption can be selected by the resistor R6. The delay in the start time of the sound can be selected by the resistor R4. The photosensor can be adjusted by selecting the resistor R1.
Kudymov Yu. S. RK-2016-04.
- 10.01.2016
The figure shows a diagram of a two-channel audio frequency power amplifier based on the LA4450 IC. The output power of the amplifier at a supply voltage of 26.4V (recommended) is 12W (per channel) into a load of 8 ohms and 20W (per channel) into a load of 4 ohms. IC LA4450 has thermal protection, protection against overvoltage and impulse noise. Main characteristics Maximum voltage …
- 25.05.2015
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- 21.09.2014
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I use this device to protect against current overloads of electrical appliances operating from a 220V network. The device has a relay load control, so it can be used in conjunction with any type of electronic equipment. The circuit consists of a current sensor (optocoupler U1) and a key on VT1 whose load is a relay. When current passes through R1 to ...
T.A. Babu
An open refrigerator door can significantly increase your energy bill. This simple device will start beeping if you leave the refrigerator door open for more than 20 seconds. When the door is open, the light comes on and the 4060B counter starts counting down. With a delay of 20 seconds, the piezo emitter begins to emit periodic sound signals, which continue, again, for 20 seconds. Then the signal is interrupted for 20 seconds. This cycle is repeated as long as the refrigerator door remains open.
Usually, either a step-down transformer or a quenching capacitor is required to obtain a low DC voltage from the mains voltage. The highlight of this project is that we do not need either one or the other. When the refrigerator door is opened, power is supplied to the light bulb through the diodes D1 ... D4 of the bridge rectifier, and through the zener diode Z1 (see figure). The voltage drop across the zener diode is smoothed out by the filter capacitor C1. This voltage is sufficient to power the rest of the circuit.
To connect the circuit, it is necessary to cut the wire going to the refrigerator light bulb as shown in the figure, and connect the circuit (shaded part of the figure) at points A and B. You can place the circuit in the compressor compartment. There are more than enough places. When the door is closed, the light is off and the circuit draws no power.
The circuit is powered directly from the mains. Therefore, caution and some idea of the device of the refrigerator would not be superfluous for you at all.
- It seems to me that now this is not relevant, all modern refrigerators already have this signaling device.
- It is not necessary to use this alarm in the refrigerator. Have you turned off the light in the bathroom, closet, hallway, etc.? Valuable solution for the formation of supply voltage. The weak point in the circuit is the protection of the diodes when the light bulb burns out, at this moment, there is often a surge of current comparable to a short circuit "knocking out the circuit breakers.
- Tell me how to apply to the bathroom? What changes to make?
- Yes, yes, I agree with this, I forgot to indicate in the first post. But I am more satisfied with options with galvanic isolation from the network, or battery options for such devices.
- When entering the bathroom, I think you won’t forget to close the door, otherwise you can accidentally find your photos on the internet :) But when you leave, you can do without a time relay. The solution couldn't be easier. If you forgot to close the door and the light is off, the squeaker will work. There will be no false positives, because first the door must be closed, and then the hand is freed to turn off the light.
- I can't agree that every refrigerator has an alarm. I don't have one, Atlant. I personally would be very annoyed by this squeak. I don’t like extraneous noises, the refrigerator is buzzing so if it squeaked it would be too much.
- I have had a refrigerator for 2 years, and I only heard the squeaker when I wiped the shelves. He does not squeak right away, but after a while only in an emergency, when they forgot to close it.
- This scheme is only suitable if the refrigerator has a light bulb. But there is a light bulb only in the large compartment, and in the freezer, which is at the bottom of the refrigerator, there is no light bulb. Unfortunately, it is the freezer that my family sometimes does not completely close. At least put the spring, as on the doors :)
- you can use a sound signaling device to fill the bathtub with water that has filled to a certain level .. or buckets for washing floors. In my opinion, you can find simple diagrams on the Internet. :)
- The refrigerator should simply be installed slightly tilted back. And that's it!
Refrigerator open alarm
The peculiarity of this signaling device is that it does not connect to the electrical circuit of the refrigerator in any way. This is just a small box that is placed inside the refrigerator. When the refrigerator door is open, the interior light turns on. The light from it hits the photodiode VD 1 and its resistance decreases sharply, the circuit in Fig.1.
Fig.1
Capacitor C1 begins to charge through the reduced resistance of the photodiode. After some time, the voltage on C1 reaches the level of a logical unit and a "tandem" of two multivibrators is launched, one of which operates at an audio frequency ( D 1.3 - D 1.4), and the second on the infrasonic ( D 1.1 - D 1.2). Connected between input and output element D 1.4, the piezoelectric sound emitter starts to beep intermittently, indicating that the refrigerator door is open for more than the charging time for C1 to a logic unit voltage.
When the refrigerator door is closed, the resistance VD 1 is high and the voltage on C1 is low and the signaling device is “silent”.
The signaling device is powered by the Krona battery. The battery has enough energy for at least one year of operation of the device.
Adjustment is to adjust the resistor R 2 so as to obtain the desired characteristics (time delay, response threshold).
The tone of the sound can be set by selecting R 3, and the interrupt frequency is R1.
J. Radio constructor
No. 12, 2004
Miniature plant watering alarm
The device shown in Fig. 2 signals that the earth in the flower pot has dried up and the plant needs to be watered., while the indicator (LED VD 2 ) shines at maximum brightness.
Fig.2
As soil moisture increases, the brightness of the LED gradually decreases, and it goes out completely. resistor R3 the brightness of the indicator of the desired humidity level is adjusted.
The circuit uses the K561TL1 chip. On elements DD 1 assembled a rectangular pulse generator. From the entrance DD 1 signal is fed to the electrode P1 and through the inverter DD 2 to electrode P2. Elements DD 3 and DD 4 control the LED. The rectangular pulses are designed to prevent oxidation of the electrodes. Long nails can be used as electrodes.
Load disconnection signaling device
The circuit signals with a luminous LED about the on state of the load, and an audible signal about the fact of the load being disconnected (or about a break in it, about a power outage), Fig.3.
Fig.3
On the direct resistance of several diodes connected in series to the load, some voltage drops. As long as the load is receiving power, this voltage is present. It is rectified by a diode rectifier. VD 10 and capacitor C1, and serves as power for the indicator LED HL 1. And also, it charges the capacitor C2, which serves as a power source for the microcircuit D1.
On chip D 1 made a sound generator. While on conclusion 5 D 1 high voltage is supplied, the generator is blocked. When the load or supply voltage is turned off, the voltage on C1 quickly decreases due to the discharge through the LED. In this case, the charge of the capacitor C2 is not consumed so quickly, since the diode interferes with this VD 11 and low current consumption chip D 1. Supply voltage D 1 is maintained, but the voltage at output 5 drops D 1. As a result, the sound generator and the piezoceramic sound emitter are launched bf 1 sounds for a while while it is powered by the charge of capacitor C2.
When the load is turned on, C1 charges quickly and blocks the sound generator.
The setting consists in selecting the number of diodes VD 1-VD 8.
D1 - chip K561LE5.
Kuzyansky L.
Literature:
1 Piet Germing. Automatic Lighting Swith
Elektor, No. 7-8, 2008.
Mains voltage failure signaling device
In any locality, short-term interruptions, "failures" of voltage in the network occur. Their duration can vary from fractions of a second to several seconds. Relatively long dips are visually noticeable - the lighting "blinked". Shorter ones go unnoticed, but may well cause the TV to switch from working to standby mode or crash the computer. It often remains unclear whether the failure occurred due to a malfunction of the device or a short-term failure of the mains voltage was the cause. The cause of both irregular and frequent short dips can be a malfunction of the contacts in the socket or plug (poorly clamped wires, weak spring contacts, oxidation of the contacts), a violation of the integrity of the cores of the stranded wire in the power cord, wear of the switch contacts.
To understand where to look for a malfunction, the proposed device will help - a signaling device for a network voltage failure. First of all, it must be plugged into a free outlet, not the one that includes the network plugs of the TV or computer. If the entire network of an apartment, office or building is faulty, then at the first voltage drop, the alarm LED will turn on. If this does not happen, but a failure occurs, it is likely that the socket to which the malfunctioning device is connected, its plug or power cord is faulty.
The next step is to connect the signaling device and the TV (computer) through a tee to the same outlet. If now the LED turns on, it means that the socket in the wall or the tee is junk. Otherwise, it remains to check the plug and power cord of the TV (computer). If they are serviceable, you will have to look for a defect in the device itself, which is prone to failures.
The diagram of the signaling device is shown in Fig.4.
Fig.4
On transistors VT1 and VT 2, the equivalent of a thyristor is assembled. When the signaling device is initially connected to the network or after an interruption in the mains voltage, the "thyristor" remains closed, and the LED HL 1 on because the transistor VT 3 open by base current flowing through resistors R5 and R 7. After pressing the button SB 1 "thyristor" will open, the voltage drop across it will become insufficient to keep the transistor open VT 3 with an LED included in its emitter circuit. The transistor will be closed and the LED off. In this (standby) state, the device will remain until the next failure of the mains voltage, as a result of which the “thyristor” closes and the LED turns on.
The mains voltage is reduced to approximately 23 V by a resistive voltage divider R1-R 3. This made it possible to apply in a rectifier bridge VD 1-VD 4 relatively low voltage diodes. The capacitance of the smoothing capacitor C1 indicated in the diagram was selected experimentally. Its decrease leads to dips in the rectified voltage at the moments when the mains sinusoid passes through zero and false alarms of the signaling device. Excessive capacitance of this capacitor increases the minimum duration of detectable dips. Ceramic capacitor C2 and inductor L 1 eliminate impulse noise that can open the "thyristor" and turn off the LED before its inclusion is noticed.
Zener diode VD 5 ensures reliable operation of the signaling device at increased mains voltage. However, even when it breaks, the voltage across the diodes VD 1-VD 4, capacitors C1, C2 and other parts of the signaling device due to the resistive divider R1-R 3 does not go beyond the limits allowed for them. To reduce the risk of electric shock in case of accidental contact with parts of the signaling device, R1 and R 3 voltage dividers are included in both network wires. Their total resistance is chosen so that the average current of the "thyristor" or the LED cannot exceed 9 ... 10 mA, even if the resistor is broken at the same time R 2 and Zener diode VD 5. The power consumed by the signaling device does not exceed 2 W.
Instead of KD522V diodes, any of the KD521, KD522 series will do. Throttle L 1 - homemade, 40 turns of any insulated thin wire on any ferrite magnetic core. A ready-made choke DM or PDM is also suitable for the inductance indicated on the diagram. A replacement for the D814A zener diode should be selected from among devices with a voltage of 5 ... 7.5 V and always in a metal case, for example, KS156A, KS168A, D808.
As a fuse FU 1, a piece of wire with a diameter of about 0.05 mm was used from the frame of a faulty microammeter. In the event of a burnout of the insert (for example, during a thunderstorm), the need to check the health of the zener diode VD 5, if necessary, replace it and only then turn on the signaling device with a new plug in the network.
HL LED 1 lights up immediately after the signaling device is connected to the network. To put the device into standby mode, just briefly press the button SB 1. After the dip is detected and the LED signal is noticed, you can press the button again to turn off the LED and return the device to standby mode.
Pankov E.
Perm
Stove gas burner burner
It is no secret that gas stoves should be used with caution. But sometimes, after removing the pan from the heat, we forget to turn off the gas burner. To get out of this situation, prompting about an oversight in time, can be a gas combustion signaling device, the diagram of which is shown in Fig. 5.
Fig.5
It is based on a multivibrator based on transistors of various structures ( VT4, VT 5), supplemented by an amplifying stage ( VT2, VT 3) with thermal sensor.
The role of the thermal sensor is performed by the transistor VT 1 located above the gas stove. per transistor VT 1 no heat is active while there is a pot or kettle on the burner. One has only to remove them, as the heat from the combustion of gas rushes up and heats the transistor VT 1. This will cause a change in the resistance of the collector-emitter section of the transistor and will lead to an increase in the voltage across the resistor R1.
The change in the signal across the resistor is amplified by a two-stage transistor amplifier VT2 and VT 3. On the collector of the transistor VT 3 there will be a significant decrease in the voltage value to such a value that the sound generator on transistors will turn on VT4 and VT 5. At this moment, an alarm signal will sound from the electrodynamic head, indicating that the gas burner is turned on and is unattended.
The tone of the signal is selected by changing the capacitance of the capacitor C1. The signaling device in standby mode consumes a current of 0.2 ... 2 mA, depending on the position of the axis of the variable resistor R 1. When a signal appears, the current consumption increases to 10 mA.
A transistor from the MP39 ... MP42 series is selected for the sensor using an ohmmeter. Connect the negative probe of the ohmmeter to the collector, positive to the emitter and fix the resistance value: if it is more than 20 kOhm, then the transistor can be used as a sensor.
The signaling device, assembled from known good parts, is immediately ready for operation. The operation of the sensor is checked by closing the collector and emitter of the transistor VT 3. In this case, a sound should be heard, when opened, the sound will disappear. Next, the scale of the variable resistor is calibrated. The sensor is installed above the lit burner, the variable resistor is set to the middle position, the signaling device is turned on and the time of the signaling device is fixed on the scale. This operation is performed at different positions of the variable resistor slider. After grading the scale, the indicator is ready for practical use.
Pestrikov V.M.
"Ham Radio Encyclopedia"
"Cover the refrigerator" signaling device
A miniature open door signaling device can be made on the K176LA7 chip (Fig. 6).
Fig.6
On elements DD 1.3 and DD 1.4 an audio frequency tone generator was assembled. The tone of the sound depends on the capacitance of the capacitor C3 and the resistance of the resistor R 3. On elements DD 1.1 and DD 1.2, another generator is assembled, periodically turning on the tone generator.
The signaling device is controlled by miniature contacts or a gecko SA 1. If the door is open (which means that the contacts are open S 1) more than 30 s (time delay depends on the resistance of the resistor R 1 and the capacitance of capacitor C2), the generator will turn on on the elements DD 1.1 and DD 1.2, the tone generator starts working and in the capsule bf 1, intermittent beeps will sound. The frequency of repetition of signals depends on the capacitance of the capacitor C1 and the resistance of the resistor R 2 (it is selected when setting up the structure).
Nechaev I.
G. Kursk
Refrigerator open door alarm
Figure 7 shows the simplest diagram of the refrigerator door open signaling device. The design is made from an old Chinese-made alarm clock.
Fig.7
Here, instead of a bell switch, a conventional photodiode from the remote control systems of old domestic TVs is turned on. It is connected in the opposite direction, that is, like a photoresistor. In the dark, its resistance is high and the alarm does not sound. When the refrigerator door is opened, the interior light comes on.
The light from it hits the photodiode and the structure located in the refrigerator starts to sound.
Temperature change alarm
One of the problems of reliable operation of electronic structures is the protection of their most important elements from overheating. For this purpose, a device has been developed, shown in Fig. 8, signaling a change in the temperature regime of such elements.
Fig.8
Its basis is a sensor on a silicon diode KD102A ( VD 1). When the temperature of the diode changes by one degree, the voltage falling at the diode terminals during forward bias changes by two millivolts. Moreover, it decreases as the temperature rises. In other words, the diode has a negative temperature coefficient of resistance.
The inverting terminal of the operational amplifier is connected to the anode of the diode. DA 1, and the reference voltage from the variable resistor engine is applied to the non-inverting output R 4, which determines the alarm threshold. When the voltage at the anode of the diode exceeds the voltage at the slider of the variable resistor, the signal at the output of the operational amplifier DA 1 is almost equal to zero. LED on HL 1 green. If the voltage at the anode becomes less than the reference voltage, a positive voltage will appear at the output of the amplifier, the LED will light up HL 2 red, warning about an increase in the temperature of the object near which (or on which) the temperature sensor is installed.
Since the operational amplifier has a large gain and is very sensitive to alternating electromagnetic fields, a capacitor C1 is installed in the feedback circuit of the operational amplifier to protect against them.
Creative workshop "Homemade"
Bobrovsky V.
Nartkala
Signaling device "Field flowers!"
A simple device, the diagram of which is shown in Fig. 9, will tell you when you need to water the plants, since when the soil dries out, a reminder signal will turn on.
Fig.9
The device reacts to the conductivity of the soil, which is highly dependent on its moisture content: the drier the soil, the worse its conductivity. Two electrodes are immersed in the soil in a flower pot and connected to the device by conductors. While the soil is damp, resistance R n is small, therefore, the voltage at the base of the transistor is low and it is closed. There is no sound signal. As the soil dries out, the resistance R n increases and at some point in time becomes such that the transistor T1 opens and the supply voltage is applied to the sound generator. There is a low, but quite distinct sound signal.
The desired tone of the signal is regulated by the selection of the capacitance of the capacitor C1. With a variable resistor R 2 set the device response threshold. At the same time, an interesting feature should be noted: as the soil dries out, its resistance gradually increases and therefore the transistor T1 gradually begins to open slightly. A soft tone is heard, the volume of which increases over time.
Electrodes 1 and 2 must be made of nichrome wire with a diameter of 0.5-1 mm. You can also use narrow strips of stainless steel.
Acoustic signaling of the arrival of guests
The simple electronic circuit shown in Fig. 10 has a high input sensitivity and is used to warn about the approach of any living object (for example, a person) to the E1 sensor.
Fig.10
The circuit is based on two elements of the K561TL1 chip ( DD 1) connected as inverters.
Foreign analogue K561TL1 - CD 4093B.
In the initial state after turning on the power at the input of the element DD 1.1, there is an indeterminate state close to a low logic level. At the exit DD 1.1 - high level, output DD 1.2 is again low. Transistor VT 1, acting as a current amplifier, is closed. Piezoelectric capsule HA1 (with internal AF generator) is not active. When touching a bare part of the human body (for example, a finger) to conclusions 1 and 2 DD 1.1, the alternating voltage induced in the human body switches elements DD 1.1, DD 1.2 to the opposite state, and they remain in it until the next effect of the pickup voltage on the input of the element DD 1.1. With the value of C1 indicated on the diagram, this electronic assembly works as a bistable trigger.
A high voltage level appears at pin 4, as a result of this transistor VT 1 opens and the capsule HA1 sounds.
By selecting the capacitance of the capacitor C1, you can change the mode of operation of the microcircuit elements. So, when the capacitance C1 decreases to 82 ... 120 pF, the node works differently. Now the beep sounds only while the input DD 1.1 affects interference - human touch.
Based on this experiment, a constant resistor is connected to the input R 1 with a resistance of 10MΩ (depending on the length of the wire to the sensor and the external installation conditions of the node). Consistently with R 1 (in that order) connect a shielded wire (cable RK-50, RK-75, shielded wire for rewriting AF signals - all types are suitable) 1 ... 1.5 m long, the shield is connected to a common wire.
It happens that the door of the refrigerator, due to inattention, remains “open, and warm air penetrates into it. From this, the temperature inside the refrigerator rises, the walls of the refrigerator chamber quickly become overgrown with a fur coat, the refrigerator electric motor turns on more and more often, which leads to increased energy consumption.
The signaling device avoids unnecessary losses. It is assembled (Fig. 64, a) “on one microcircuit and consists of two generators, one of which is tone, assembled on elements DD1.3, DD1.4, switched on by the second generator on elements DD1.1, DD1.2. The operation of the signaling device is controlled by the SA1 contacts installed on the refrigerator body, opposite its door.
In standby mode, when the refrigerator door is tightly closed, the contacts are closed, none of the generators works. In this mode, the signaling device consumes a current determined by the resistance of the resistor R1 and the leakage current of the microcircuit.
If the refrigerator door is open for a long time or is not tightly closed, the capacitor C2 is charged through the resistor R1, and when the voltage across it reaches a high level, the generator will start working on the elements DD1.1, DD1.2. The pulse repetition rate is approximately 1 Hz. At the same frequency, the tone generator is turned on and off. Thus, if the refrigerator door is open for a certain time, then an intermittent sound signal will be heard in the telephone BP1.
The duration of the delay in the sound signal depends on the resistance of the resistor R1 and the capacitance of the capacitor C2. When the door is closed, the capacitor quickly discharges through the closed contacts SA1 and the signaling device goes into standby mode. If the door is opened / for a long time, for example, to defrost the refrigerator, then for this time the signaling device power supply is turned off by a special switch or simply by disconnecting the GB1 battery.
Rice. Fig. 64. Signaling device circuit (a), SA1 contact design (b) and signaling device circuit board (c)
The fixed part of the SA1 node is a piece of foil textolite with a thickness of not more than 0.5 mm (Fig. 64, b) with two contact pads. The textolite is glued to the refrigerator body opposite the rubber door seal. The second part of the assembly is a smaller piece of foil glued to the rubber seal opposite the first part. With the door closed, this segment should close the contact pads.
The BF1 phone must be high-resistance, the power source can be a Krona, Corundum battery or two 3336, Rubin batteries connected in series. The circuit board is shown in fig. 64, in.
The delay time of the signaling device is set by selecting the capacitance of the capacitor C2, the required tone of the signal - by the capacitor C3, and the frequency of the signal - by selecting the capacitance of the capacitor C1.
References: I. A. Nechaev, Mass Radio Library (MRB), Issue 1172, 1992.