DD210484A1 - ELECTRONIC THERMOSTAT WITH DIGITAL TEMPERATURE INDICATOR - Google Patents

Abstract

The electronic thermostat with digital temperature display is used for temperature control of refrigeration systems, in particular household refrigerators, with simultaneous digital temperature display and is mainly used in the air conditioning and refrigeration technology. The object of the invention is to combine the basic characteristics of the digital temperature display, which is time multiplexed for several digits for reasons of energy saving, with necessities of control (ignition pulses) power electronic components. The solution according to the invention is characterized by electrical temperature measurement and nominal value-dependent ignition pulse control of the refrigeration machine.

Description

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Title of the invention;

Electronic thermostat with digital temperature display

Field of application of the invention;

The electronic thermostat with digital temperature display is used to control cooling systems, especially household refrigerators, with gleichseitiger display of the temperature conditions reached. It is especially used in the field of small refrigeration systems, cold rooms and climatic chambers,

Characteristic of the known technical solutions

Thermostats for refrigeration units are in DE-OS 2413509 Kl. 25 3 49/00 and in the EE-OS 195ISO? Cl. 17 a 4/02 described. In both documents, technical solutions are presented, which provide a regulation of the refrigeration system via thermistors or temperature-dependent 7 / iderstände, wherein the falling between input and output voltage is compared with a setpoint and a Differenzialkomperator the power levels of the chiller or controls via an operational amplifier against each other Transistor stages Press relays that switch a compressor.

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Both solutions have the drawback that a power control can take place only in three stages, whereby an accurate control is impossible. In addition, in both cases, no Istv / ertanzeige the temperatures reached is provided.

Simple devices for controlling the temperature of refrigeration systems are based on thermostats that directly switch a drive motor. Due to high switching frequency and large switching currents, the contacts of these thermostats are subject to relatively high wear. Therefore, in the last Since Isistungselektronische components such as Z-. B. thyristors or triacs used to switch the prime mover of the refrigeration system. The ignition of these components is due to the high start-up currents in the auxiliary winding of the chiller not directly possible by the thermal state, but must be done via a separate pulse generator to ensure a fast and secure ignition of power electronic components and to prevent the so-called "burn-in" - The pulse generator is controlled by a thermostat.

A disadvantage of this arrangement is the 'relatively high cost of electronic components, associated with a high price, low reliability and large volume and power requirements. The latter is particularly important in the field of domestic refrigerators of importance, where at a total demand of about 70 W / 1 W power loss of the electronics percentage in the order of the 'efficiency differences of engines from different manufacturers.

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The temperature display on household refrigerators was previously with conventional 'thermometers inside the unit. This is an open, combined with loss of cold and moisture absorption necessary. Mechanical and electrical thermometers with Auöenanzeige are usually not used because of the high cost.

Aim of the invention;

The object of the invention is to provide an electronic thermostat with digital temperature display, which consists of a few components and allows accurate control and optimum measurement, the energy consumption is reduced to a minimum compared to conventional thermostats.

Explanation of the essence of the invention:

Object of the invention 'is to produce an electronic thermostat with digital temperature display, which consists of as few components and the basic characteristics of the digital temperature display, which takes place for several digits zeitmultiples, combined with necessities of the control power electronic components.

3rfindungsgemä3 the object is achieved dai3 the temperature measurement is carried out electrically, for. 3. About a HeiSleiter, a resistance thermometer or a Pnübergang a semiconductor. The voltage dropped on the electric thermometer is amplified so that the temperature and the amplifier output voltage are equivalent (i.e., 1 grd ^ 1 mV or 1 7). This tension will

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fed to a running as an integrated circuit A / D converter and brought as a temperature for display. At the same time, this voltage is fed to a comparator where it is compared to a preset set point. The comparator output is fed to the time-divisional clock of the digit display of the A / D converter to an AND gate. If the temperature value of the cooling space is above the setpoint value, then pulses with the clock frequency of the time-division multiplex of the A / D converter are obtained at the output of the ÜITD gate. Pigtail be optionally supplied after further amplification directly or indirectly via an isolation transformer or optocoupler the gate of a triac or thyristor, which is thereby ignited and turns on the chiller. The chiller runs as long as the setpoint is below the actual value. In order not to exceed the permissible switching frequency of the motor, it may be sensible to use a trigger with the corresponding Heutraizone or a made by z, 3, large mass inertial temperature sensor instead of the Kcmperators. Ss. It is also conceivable not to carry out the nominal-actual comparison analogously with a comparator, but to compare the value output by the A / D converter with a numerical value set at a pre-selection switch. However, the economically more favorable variant seems to be the analogue comparator. The setpoint input can be z. 3. with the aid of an additional key, make sure that a voltage drop analogous to the thermometer is made via the solid-state potentiometer as potentiometer and that this "temperature" is displayed via the A / D converter. Of course, here is the ül ~ D-member blocked for Zündimpuiserzeugung to prevent faulty operation of the engine.

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The invention will be explained in more detail in the following embodiment. The accompanying drawing shows a schematic representation of a device according to the invention.

Sin resistance thermometer (i) is traversed by constant current. The temperature-proportional voltage dropping above it is amplified in an amplifier (2). At the same time, in this amplifier (2), the preset zero value at the hull point adjuster / 3) is added. The amplifier output voltage 7/1 is once supplied to the A / D converter (p) , which is designed as an IC, whose output values control the digital display ()) via a BCD su segment converter (8). File, the individual digits are successively switched through by the multiplexing lines (1 2).

On the other hand, the output voltage of the amplifier (2) is compared in a comparator [4] with a value set on the soli value divider (5). If there is a need for refrigeration, this is done on the expander (4) an output signal which is sent by one of the multiplexers (12) in the gate i ^ 9). At the output of the gate (9) pulses are generated with the frequency of the multiplier clock Ignite the triac (JO), causing the chiller (ii) to start. If the cold room temperature has fallen below the set soli value, the output signal disappears at the comparator ^ 4), so that the ignition pulses at the triac \ j10), the chiller remain standing.

Claims (1)

243649 5 invention claim 1. Electronic thermostat with digital "temperature display for controlling the temperature of refrigeration systems, especially of HaushaltsküMschränken," with simultaneous digital 'temperature display, characterized in that the temperature measurement takes place electrically   and logically linking the tachometer clock of a digital temperature display to a target value dependent comparator signal to realize the impulse pulse generation for the string machine motor via a triac, the temperature measurement preferably being with a temperature dependent resistor or a ph-semiconductor transition and reducing the peak frequency Comparator replaced by a trigger bzv /. the thermometer can be made sluggish by larger mass .. 2, electronic thermostat with digital temperature display according to item 1, characterized in that the desired-Ist- "equalization is not analog with a comparator, but that the output signal of the Α / Ό-Wandiers is compared with a numerical value set at a preset switch · 1 salt