EP1100100B1 - A circuit for detecting the state of electrical switches - Google Patents
A circuit for detecting the state of electrical switchesInfo
- Publication number
- EP1100100B1 EP1100100B1 EP00124515A EP00124515A EP1100100B1 EP 1100100 B1 EP1100100 B1 EP 1100100B1 EP 00124515 A EP00124515 A EP 00124515A EP 00124515 A EP00124515 A EP 00124515A EP 1100100 B1 EP1100100 B1 EP 1100100B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- switch
- state
- signal
- circuit according
- switches
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000003745 diagnosis Methods 0.000 claims description 16
- 238000012544 monitoring process Methods 0.000 claims description 16
- 230000007257 malfunction Effects 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 7
- 230000004913 activation Effects 0.000 claims description 4
- 238000001514 detection method Methods 0.000 claims description 2
- 230000002688 persistence Effects 0.000 claims description 2
- 230000008859 change Effects 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 238000010276 construction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000003071 parasitic effect Effects 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H9/00—Details of switching devices, not covered by groups H01H1/00 - H01H7/00
- H01H9/16—Indicators for switching condition, e.g. "on" or "off"
- H01H9/167—Circuits for remote indication
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H1/00—Contacts
- H01H1/0015—Means for testing or for inspecting contacts, e.g. wear indicator
Definitions
- the present invention relates in general to a circuit for detecting the state of electrical switches.
- the invention relates to a circuit of the type described in the preamble to Claim 1, for reading the state (open/closed) of electrical switches, particularly for automotive applications, as well as for the diagnosis of a possible damaged condition of the contacts of the switches.
- Electronic control units provided for managing information connected with the instantaneous states adopted by these switches and for undertaking predetermined actions as a result of a change thereof, are therefore required to monitor these states continuously.
- Information regarding the instantaneous state of a switch is generally acquired by the provision of a network (for example, this may simply be a resistive divider) which supplies the switch and which detects the voltage established at the terminals of the switch and compares its value with one or more threshold values.
- a network for example, this may simply be a resistive divider
- Switches fitted in motor vehicles are generally exposed to moisture, dirt and other atmospheric agents with the result that they undergo damage to their contacts and, in some cases, exhibit a general malfunction condition.
- an electrical switch which in an open state would have an equivalent resistance of the order of 100 k ⁇ or more may have a greatly reduced equivalent resistance (of the order of a few k ⁇ ) because an undesired current path is established between the contacts.
- each switch is constantly supplied with a cleaning current of considerable intensity and the value of the voltage which is established at its terminals is transferred to the input of a processing and control unit where it is converted into a digital signal and stored.
- this method does not permit quantitative diagnosis of a condition of damage to the contacts of the switch, that is, it cannot recognize whether a certain voltage value at the terminals of the switch results from a corresponding actual operative state or from a condition of excessive damage.
- control unit In all of these cases it would instead be preferable, in the absence of events, for the control unit to operate in an operative state of low current consumption, for example, in order not to discharge the battery of the vehicle, but to be able to recognize correctly the operative state of a switch and/or a possible malfunction condition thereof.
- the object of the present invention is therefore to provide a satisfactory solution to the problems set out above, preventing the problems of the prior art. According to the present invention, this object is achieved by means of a circuit having the characteristics recited in Claim 1.
- the present invention is based on the principle of supplying the switches continuously with a monitoring current of low intensity so as to satisfy the requirements of low consumption and, selectively, in dependence on the detection of a presumed change in the state of a switch, with a diagnosis current of greater intensity in order to check that the event has actually occurred or to reveal a condition of damage to the switch.
- the supply of the monitoring current permits continuous monitoring of the state of a switch and qualitative recognition of cases in which the switch has a low or almost zero equivalent resistance (and hence a voltage below a first predetermined threshold value at its terminals) or a very high equivalent resistance (and hence a voltage above a second predetermined threshold value at its terminals).
- a low or almost zero equivalent resistance may be due to the closed state of the switch, but also to a condition of damage thereto which is present in an open state, when the control unit recognizes that this situation has arisen, the control unit is arranged to supply the diagnosis current and to take a further reading of the state of the switch.
- the network for supplying the switches includes, for each switch, a pair of circuit branches, each of which is supplied by a corresponding supply voltage and which, in the currently-preferred embodiment, constitute, with the switches, resistive dividers.
- the supply voltages and the resistive components of these branches are advantageously selected in a manner such that, for a equivalent resistance value which is typical of a condition of damage to the switch so that this condition is interpreted as a closed state of the switch when it is supplied solely with the monitoring current, the supply by means of the diagnosis current enables the open state of the switch to be detected correctly, thus giving rise to two different readings.
- the supply voltages and the resistive components of the supply network are also advantageously selected in a manner such that the closed state of a switch and the open state in an undamaged condition are interpreted in the same manner in both supply situations.
- the control unit is then arranged to warn the user of the vehicle of the appearance of a malfunction condition when there are differing readings, and to undertake cyclically a checking procedure to ascertain whether a correct operating condition has been re-established.
- the switches are also connected to a microprocessor control unit P via respective connection lines, for example, for the switches SW 1 and SW 2 , the lines 10, 20 each of which is connected at one end to the corresponding node N i and at the other end to an activation input IRQ i and to a reading input RD i of the control unit P.
- the supply network includes first and second circuit branches connected to each switch via the respective node N i and supplied by means of corresponding terminals VS 1 and VS 2 , respectively.
- a first supply circuit branch B 1 to the supply terminal VS 1 of which a first supply voltage V cc is applied, comprises a resistor R 1 interposed between the supply terminal and the node N 1 .
- a second supply circuit branch B 2 to the supply terminal VS 2 of which a second supply voltage V B is selectively applied comprises a resistor R 2 and a diode D connected in series therewith, with its cathode connected to the node N 1 .
- the supply terminal VS 2 is connected to a battery B (for example, the 12V battery of the vehicle, in automotive applications) by means of the emitter-collector path of a switch Q.
- a single switch Q is common to all of the second circuit paths B 2 and is formed by a bipolar transistor the base terminal of which is connected to an output EN of the control unit P.
- the connection of the diodes D in the branches B 2 prevents the monitoring current supplied to the switch SW 2 from flowing from the respective branch B 1 , through the respective branch B 2 and the branch B 2 relating to SW 1 , towards the switch SW 1 , upon closure of the switch SW 1 , confusing the reading of the voltage at the node N 1 .
- An electrical switch approximates to the behaviour of an ideal switch SW id (short-circuit in a closed state, open circuit in an open state), except for a resistive component in series, indicated R s , which intervenes in a closed state and is of the order of a few tens of ohms (the value typically recognized for an on/off switch or a diverter switch for applications in the automotive field is 25 ⁇ ), and except for a resistive component in parallel, indicated Rp which takes account of any parasitic current path between the contacts of the switch due to conditions of wear and dirtiness.
- the resistive component R p in parallel is of the order of hundreds of k ⁇ ; in a damaged switch, the value typically recognized for the resistive component R p is 2k ⁇ .
- the supply voltage V cc applied to the terminal VS 1 of the first circuit branch is preferably 5V (and corresponds to the supply voltage of the control unit P), whereas the supply voltage V B applied selectively to the terminal VS 2 of the second circuit branch is derived directly from the battery B (and is therefore about 12V).
- the values of the resistors R 1 and R 2 are preferably 47k ⁇ and 1k ⁇ , respectively.
- the signal indicative of the state of a switch is acquired by detecting the voltage which is established at its terminals.
- each switch SW i is supplied with a monitoring current exclusively via the respective first circuit branch B 1 .
- the control unit P is therefore able to monitor the (normally open) state of each switch continuously, operating in a state of low current consumption (of the order of hundredths of a mA).
- the voltage detected at the node N i is determined by the resistive divider constituted by the resistor R 1 and by the equivalent resistance of the switch.
- the equivalent resistance of a closed switch adopts a value substantially equal to R s (almost zero) and the voltage at the corresponding node N i adopts a value close to the earth potential and in any case within a first range of values or below a predetermined first threshold value.
- the control unit P receives this voltage value at the corresponding input IRQ i and interprets it as a low logic level binary signal.
- a monitoring current of the order of a tenth of a mA flows through the switch.
- the equivalent resistance R p is of the order of hundreds of k ⁇ or more and the supply voltage V cc is divided and is established predominantly at the terminals of the switch.
- the voltage at the corresponding node N i adopts a value within a second range of values or above a predetermined second threshold value.
- the control unit P receives this voltage value at the corresponding input IRQ i and interprets it as a high logic level binary signal.
- a situation of this type also arises when a switch undergoes excessive damage to its contacts and its equivalent resistance R p in the open state adopts a low value (of the order of 2 k ⁇ ) much lower than R 1 .
- the supply voltage V cc is divided and is established predominantly at the terminals of R 1 and, although the voltage at the node N i is not close to the earth potential, it nevertheless adopts a value within the first range of values or below the first threshold value, which is again interpreted as a low logic level binary signal.
- control unit Every time the control unit is activated, it is arranged to take a further reading of the state of the switch in order to distinguish which event has actually occurred.
- the voltage detected at the node N i is now determined substantially by the resistive divider constituted by the emitter-collector path of the switch Q, by the resistor R 2 , by the diode D polarized directly, and by the equivalent resistance of the switch.
- a diagnosis current of the order of a few mA flows through the switch.
- the equivalent resistance R p is of the order of one k ⁇ , but is still comparable with R 2 so that the supply voltage V B is divided and is established predominantly at the terminals of the switch and the voltage at the corresponding node N i again adopts a value within the second range of values or above the second threshold value, and the control unit interprets this value correctly as a high logic level binary signal.
- the control unit correctly recognizes the closed state of the switch and undertakes the predetermined actions resulting from this event.
- control unit If the control unit has detected a general condition of malfunction of a switch, it warns the user of the vehicle of this condition and is arranged to perform cyclically a checking procedure to ascertain whether a correct operating condition has been re-established.
- the control unit prevents the supply of the diagnosis current, arranging the network for supplying the switches to operate with the monitoring current alone (switch Q non-conductive). Cyclically, after a waiting period of predetermined duration, it reads the states of the switches at two successive moments by supplying them by means of the monitoring current and by means of the diagnosis current, respectively.
- the persistence of the malfunction condition is recognized and the unit is arranged for a further diagnosis when a subsequent waiting period has elapsed.
- the unit advantageously starts to operate in the normal operative condition again, and is set to await an event (supply with low current consumption).
- the invention is not limited purely to the preferred embodiment described fully by way of example, in which the signal indicative of the state of a switch is acquired by detecting the voltage at the terminals of the switch, but further embodiments in which this signal is acquired at other points of the circuit branches for supplying the switches are also envisaged.
Landscapes
- Keying Circuit Devices (AREA)
- Electronic Switches (AREA)
- Transmitters (AREA)
- Electrophonic Musical Instruments (AREA)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
ITTO990969 | 1999-11-12 | ||
IT1999TO000969A IT1311343B1 (it) | 1999-11-12 | 1999-11-12 | Circuito per il rilevamento dello stato di interruttori elettrici. |
Publications (2)
Publication Number | Publication Date |
---|---|
EP1100100A1 EP1100100A1 (en) | 2001-05-16 |
EP1100100B1 true EP1100100B1 (en) | 2006-10-04 |
Family
ID=11418199
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP00124515A Expired - Lifetime EP1100100B1 (en) | 1999-11-12 | 2000-11-09 | A circuit for detecting the state of electrical switches |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP1100100B1 (it) |
DE (1) | DE60031069T2 (it) |
ES (1) | ES2267448T3 (it) |
IT (1) | IT1311343B1 (it) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN105785264A (zh) * | 2016-04-25 | 2016-07-20 | 首瑞(天津)电气设备有限公司 | 断路器状态监测装置 |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4026418B2 (ja) | 2002-06-05 | 2007-12-26 | 株式会社デンソー | スイッチ状態検出装置 |
DE10244534B4 (de) * | 2002-09-25 | 2012-03-01 | Nucellsys Gmbh | Schaltungsanordnung sowie Verfahren zur Erkennung von Fehlersituationen in gekoppelten Systemen |
FR3006462B1 (fr) | 2013-05-30 | 2015-07-03 | Continental Automotive France | Procede et dispositif de lecture de l'etat de variables de contact d'un vehicule automobile |
FR3024794B1 (fr) | 2014-08-05 | 2016-09-02 | Continental Automotive France | Procede d'acquisition de signaux, tels que signaux representatifs de l'etat de contacts d'un vehicule automobile |
FR3080399B1 (fr) * | 2018-04-18 | 2023-11-24 | Psa Automobiles Sa | Procede de commande d’une serrure electrique permettant de diagnostiquer une defaillance de la commande d’ouverture associee, commande d’ouverture et vehicule mettant en œuvre un tel procede |
IT201900006846A1 (it) * | 2019-05-15 | 2020-11-15 | Geox Spa | Circuito di controllo per un indumento luminoso e metodo di attivazione di sorgenti luminose su indumenti |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2921095C2 (de) * | 1979-05-22 | 1983-03-31 | Auergesellschaft Gmbh, 1000 Berlin | Verfahren zur Überwachung des Schaltzustandes von Schaltelementen |
JPH073465B2 (ja) * | 1986-09-12 | 1995-01-18 | オムロン株式会社 | スイツチ機構 |
DE3724926A1 (de) * | 1987-07-28 | 1989-02-09 | Bayerische Motoren Werke Ag | Schaltungsanordnung zur ueberpruefung der zuleitungen eines schalters oder sensors |
DE4015271A1 (de) * | 1990-05-12 | 1991-11-14 | Vdo Schindling | Schaltungsanordnung zur abfrage von schalterstellungen |
FR2682528B1 (fr) * | 1991-10-15 | 1997-01-31 | Alsthom Gec | Dispositif pour la determination de l'etat d'un appareil et en particulier de l'etat ouvert ou ferme d'un appareil electrique a l'aide de contacts auxiliaires. |
US5772205A (en) * | 1995-10-27 | 1998-06-30 | Coldebella; Mark J. | System to detect inoperative switches in an amusement device |
US5714852A (en) * | 1996-09-13 | 1998-02-03 | United Technologies Automotive, Inc. | Three state switch detection using current sensing |
-
1999
- 1999-11-12 IT IT1999TO000969A patent/IT1311343B1/it active
-
2000
- 2000-11-09 EP EP00124515A patent/EP1100100B1/en not_active Expired - Lifetime
- 2000-11-09 DE DE60031069T patent/DE60031069T2/de not_active Expired - Lifetime
- 2000-11-09 ES ES00124515T patent/ES2267448T3/es not_active Expired - Lifetime
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN105785264A (zh) * | 2016-04-25 | 2016-07-20 | 首瑞(天津)电气设备有限公司 | 断路器状态监测装置 |
CN105785264B (zh) * | 2016-04-25 | 2018-06-08 | 首瑞(天津)电气设备有限公司 | 断路器状态监测装置 |
Also Published As
Publication number | Publication date |
---|---|
DE60031069T2 (de) | 2007-02-08 |
ITTO990969A0 (it) | 1999-11-12 |
EP1100100A1 (en) | 2001-05-16 |
ITTO990969A1 (it) | 2001-05-12 |
IT1311343B1 (it) | 2002-03-12 |
DE60031069D1 (de) | 2006-11-16 |
ES2267448T3 (es) | 2007-03-16 |
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