CN1287272A

CN1287272A - DC motor tachometer

Info

Publication number: CN1287272A
Application number: CN 99118968
Authority: CN
Inventors: 陈俊宏
Original assignee: ZHENCHEN SCIENCE & TECHNOLOGY Co Ltd
Current assignee: ZHENCHEN SCIENCE & TECHNOLOGY Co Ltd
Priority date: 1999-09-03
Filing date: 1999-09-03
Publication date: 2001-03-14

Abstract

DC motor tachometer includes a pulse coupler connected to a power wire for a DC motor, a single-shot circuit, a tachometer circuit, a comparator and an alarm connected successively. The single-shot circuit is triggered by the pulse coupler to produce a square wave voltage to be measured, the tachometer circuit converts the square wave voltage into a voltage to be measured, the comparator compares the voltage to be measured with a critical voltage and outputs one low rotation speed signal when the voltage to be measured is lower than the critical voltage, and the alarm outputs one warning signal after receiving the low rotation speed signal.

Description

DC motor tachometer

The present invention relates to a kind of DC motor tachometer, particularly relate to a kind of do not need to change direct current drive machine and lower-cost DC motor tachometer; This DC motor tachometer is specially adapted on the fan.

Electronic device and equipment Chang Bixu dispel the heat by fan, avoid the overheated damage that causes, make the electronic device can normal operation, yet, the direct current motor of use on fan, after use after a while, can be because the rotating shaft of motor self wearing and tearing or other mechanical reasons, make motor speed descend, and the heat dissipation that fan provided that is driven by it is greatly reduced, even cause the instrument and equipment that uses this fan to break down or damage, therefore, it is necessary monitoring for the rotating speed of direct current motor.The technology that generally is used for the direct current motor that is used in fan is carried out rotation speed monitoring mainly contains two kinds, the one, adopt the optically-coupled mode, another is the magnetic field induction mode, but this dual mode is when implementing, must be earlier the device of direct current motor be carried out to a certain degree change, and the element cost is higher, therefore, no matter be very not convenient for the fabricator or the user that use direct current motor.

The object of the present invention is to provide a kind of direct current drive machine and DC motor tachometer with low cost of need not changing.

For the present invention that achieves the above object takes following measure:

DC motor tachometer of the present invention is characterized in that: comprise a pulse wave coupling mechanism, an one shots, a tachometer circuit, a comparer and an attention device;

The pulse wave coupling mechanism is electrically connected with the power lead of direct current motor, and exports a coupled voltages;

One shots is electrically connected with the pulse wave coupling mechanism, and is subjected to coupled voltages triggering for generating one square-wave voltage to be measured of this pulse wave coupling mechanism;

Tachometer circuit is electrically connected with one shots, converts the magnitude of voltage to be measured of simulation in order to the square-wave voltage to be measured with one shots output;

Comparer is electrically connected with tachometer circuit, and is provided with a critical voltage value, in order to the magnitude of voltage to be measured of reception tachometer circuit output, and compares, and can export a slow-speed of revolution signal when magnitude of voltage to be measured is lower than the critical voltage value of simulation;

Attention device is electrically connected with comparer, an exportable alarm signal when receiving the slow-speed of revolution signal of comparer output.

Wherein: described attention device can be a buzzer.

Wherein: described attention device can be a light-emitting component.

Wherein: described critical voltage value can be a simulation critical voltage value.

Wherein: described critical voltage value can be a digital critical voltage numerical value.

The present invention is described in detail below in conjunction with drawings and Examples:

Description of drawings:

Fig. 1 is the circuit side figure of the embodiment of the invention.

Fig. 2 is the circuit diagram of DC motor tachometer embodiment of the present invention.

Fig. 3 is the schematic perspective view of the embodiment of the invention.

Fig. 4 is the current waveform synoptic diagram of the power supply of dc motor line of the embodiment of the invention.

Shown in Fig. 1～3, DC motor tachometer of the present invention is performed on the fan 1 that uses direct current motor, this fan 1 comprises a fan body 10, an one direct current motor 20 and a DC motor tachometer 30, direct current motor 20 is to be used for drive fan body 10, this DC motor tachometer is then contacted with the circumscripted power line 21 of direct current motor 20, DC motor tachometer 30 can be external in fan 1, or be directly installed on appropriate location in the fan body 10 as shown in Figure 3, form the some of fan 1 jointly.

Direct current motor 20 can be brushless DC motor or brush direct current motor, and according to the characteristic of direct current motor, the current waveform on its power lead 21 is incited somebody to action continuous negative pulse as shown in Figure 4.

Cooperate shown in Fig. 1,2, DC motor tachometer 30 comprises a pulse wave coupling mechanism 31, one shots 32, a tachometer circuit 33, a comparer 34 and an attention device 35.

21 one-tenth electrical connections of power lead of pulse wave coupling mechanism 31 and direct current motor 20.

One shots 32 is electrically connected with pulse wave coupling mechanism 31, and the coupled voltages triggered response that is subjected to pulse wave coupling mechanism 31 produces a square-wave voltage to be measured, this square-wave voltage to be measured is the continuous square wave of certain width, when the rotating speed of direct current motor 20 is healed high, then the spacing between this square wave and square wave is littler, so average voltage level is higher, otherwise then lower.

Tachometer circuit 33 is electrically connected with one shots 32, in order to the square wave pulse wave electric voltage to be measured of one shots 32 outputs is handled in simulation (or with numeral) mode, converts simulation magnitude of voltage to be measured (or converting digital average counter value to be measured to) to.

Comparer 34 is electrically connected and is preset with a critical voltage value (or critical numerical value) with tachometer circuit 33, in order to receive the magnitude of voltage to be measured of tachometer circuit 33 outputs, and compare, magnitude of voltage subcritical magnitude of voltage to be measured (or average counter value subcritical numerical value to be measured of tachometer circuit 33 outputs) when tachometer circuit 33 outputs, then a slow-speed of revolution signal is exported in response, and critical voltage value and critical numerical value are to set according to direct current motor 20 required output minimum speeds.

Attention device 35 is electrically connected with comparer 34, and when receiving the slow-speed of revolution signal of comparer 34 outputs, then an alarm signal is exported in response, and attention device 35 can be luminophors such as buzzer or light emitting diode.

In the present embodiment, pulse wave coupling mechanism 31 mainly comprises three transistor Q1, Q2, Q3, two resistor R 1, R2 and capacitor C1, and transistor Q2 directly is electrically connected with the power lead 21 of direct current motor 20; Export a coupled voltages through capacitor C1.

One shots 32 mainly comprises two transistor Q4, Q5, five resistor R 3, R4, R5, R6, R7 and capacitor C2, wherein resistor R 3 directly is electrically connected with the capacitor C1 of pulse wave coupling mechanism 31, and be subjected to trigger by the coupled voltages of capacitor C1 output, producing a square-wave voltage to be measured, this square-wave voltage to be measured is the continuous square wave of certain width, if the rotating speed of direct current motor 20 is high more, spacing between square wave then to be measured and square wave is more little, so average current is high more, on the contrary then lower.

Tachometer circuit 33, mainly comprise a resistor R 8 and a capacitor C3, wherein resistor R 8 directly is with the resistor R 6 of one shots 32 and is electrically connected, utilize tachometer circuit 33 to be able to and to convert analog magnitude of voltage to be measured to or further to convert digital average counter value to be measured to via the square wave pulse wave electric voltage to be measured of resistor R 6 output with simulation or further handle with digital form.

Comparer 34, mainly comprise two operational amplifiers and four resistor R 9, R10, R11, R12, comparer 34 directly is electrically connected with above-mentioned tachometer circuit 33, and predetermined critical voltage value or critical numerical value arranged, if the voltage average counter value to be measured of tachometer circuit 33 outputs is lower than this critical voltage value, or the average counter value subcritical numerical value to be measured of tachometer circuit 33 outputs, then export a slow-speed of revolution signal; Critical voltage value and critical numerical value are to set according to direct current motor 20 required output minimum speeds.

Compared with prior art, the present invention has following effect:

From the above, when direct current motor 20 after long-term the use, its rotating shaft (figure do not show) is worn and when the output speed of direct current motor 20 is reduced, as shown in Figure 4, in the current waveform on power lead 21, the spacing L1 of continuous two negative pulses will be elongated, and be coupled to the square-wave voltage to be measured that one shots 32 is exported via pulse wave coupling mechanism 31, the spacing L2 of continuous two square waves is relatively elongated, therefore, simulation mean direct voltage value will reduce (or the average counter value of numeral reduces), also since tachometer circuit 33 change the taking-up magnitude of voltage to be measured (or average counter value to be measured) can decrease, in case the magnitude of voltage to be measured of simulation is lower than default critical voltage value when being lower than default critical numerical value (or the average counter value to be measured of numerical digit), comparer 34 is promptly exported a slow-speed of revolution signal to attention device 35, make attention device 35 send alarm signals such as the sound or light, like this, when in case the heat sinking function that the reduction of the rotating speed of direct current motor 20 causes fan 10 to be provided is not good, the user just can obtain caution immediately, and repair or replace work, avoid using instrument or equipment failure or the damage of fan 10 as the heat radiation instrument.By said apparatus as can be known, when implementing, needn't change the device of direct current motor fully, and required element cost is lower.

Claims

1. a DC motor tachometer is characterized in that: comprise a pulse wave coupling mechanism, an one shots, a tachometer circuit, a comparer and an attention device;

2. DC motor tachometer as claimed in claim 1 is characterized in that:

Described attention device is a buzzer.

3. DC motor tachometer as claimed in claim 1 is characterized in that:

Described attention device is a light-emitting component.

4. DC motor tachometer as claimed in claim 1 is characterized in that:

Described critical voltage value is a simulation critical voltage value.

5. DC motor tachometer as claimed in claim 1 is characterized in that:

Described critical voltage value is a digital critical voltage numerical value.