CA2031037C - Flasher switch circuit independent of polarity of supply - Google Patents
Flasher switch circuit independent of polarity of supplyInfo
- Publication number
- CA2031037C CA2031037C CA 2031037 CA2031037A CA2031037C CA 2031037 C CA2031037 C CA 2031037C CA 2031037 CA2031037 CA 2031037 CA 2031037 A CA2031037 A CA 2031037A CA 2031037 C CA2031037 C CA 2031037C
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Abstract
A two pin switch for automobile direction signal flashers is wired so that the prongs of the switch may be plugged into the respective socket in either orientation, i.e, the switch is independent of polarity. The switch comprises a relay having a driven circuit to throw the relay on a signal of specific polarity. Both prongs are connected into both the driven circuit and diode bridges are provided to block transmission of negative signal to the driven positive terminal and to block transmission of positive signal to the driven negative terminal and to block transmission of signal other than that of the specific polarity to throw the relay.
Description
This invention relates to electronic flasher switches which can be utilized in automotive applications, for example, flashing turn direction indicators.
Various designs of flasher switches have been made in the past. Thermal flasher switches incorporating a bi-metal construction designed to be activated upon resistance heating and expansion of metal components continue to be in frequent use. Such units are popular due to relatively low cost of manufacture. They may be of very simple construction, requiring only a connector pin to the electrical supply and a connector pin to the load. The supply may be either of positive or negative polarity. Such switches may be operated with two connection pins, but have frequently been provided with another pole and a third pin to allow for additional services to the automobile driver, such as the provision of an independent dashboard light indicating serviceability of the system. Disadvantages such as temperature sensitivity and limited lifespan make thermal switches less favourable in a wide variety of heavy duty applications such as in trucks.
Flasher switches incorporating single pole, single throw relays have also been used. Again, these devices are relatively robust. Such flasher switches have been designed for operation under either fixed load or variable load conditions.
With the introduction of sophisticated integrated circuits, it became possible to control the operation of a relay through an integrated circuit (IC). Flasher switches utilizing this technology required three pins, since a ground for the IC was necessary. Overload protection and short circuit protection is normally regarded as necessary for such devices. These devices were also strictly operable in circuits of one polarity only. Thus, if such a device were connected into a circuit "back to front", it would not operate.
Nevertheless, such devices have various advantages. These electronic flashers utilizing IC were, in their early embodiment, unsuitable for the replacement of failed devices unless these were of a similar design. One reason for this was the necessity for utilizing three pins in the improved device while the failed devices would be of the two-pin type and hence suitable connections from the new device would not be present. This difficulty was addressed in Canadian Patent Application No. 595,229, filed March 30, 1989, inventor, Rodney Hayden. That patent application described and claimed a directional flasher switch incorporating an IC and designed to operate without a ground so that only two pins are required. The switch of that patent application is, however, dependent on polarity and thus is not suitable for a replacement part unless the wiring into which it is to be incorporated is of proper polarity.
An attempt has now been made to provide a flasher switch utilizing circuit having electronic relay control and which may be tolerant to connection into a circuit of either polarity.
According to the invention, there is provided a flasher switch reversibly operable with a DC power source and a load including: a first terminal adapted for connection to either one of the DC power source and the load; a second terminal adapted for connection to the DC power source when the first terminal is connected to the load and to the load when the first terminal is connected to the DC power source; a relay connected to open and close a load circuit; drive means for the relay having a positive input terminal for positive input connected to each of the first and second terminals, a negative input terminal for negative input connected to each of the first and second terminals, and a sense input terminal connected to each of the first and second terminals, the drive means being adapted to open and close the load circuit in response to signals applied to the sense input terminal; first means to block transmission of negative signal to the positive input terminal; second means to block transmission of positive signal to the negative input terminal; and third means to block transmission of signal other than that of a specific relative polarity to the sense input terminal when the load circuit is open and to present signal of a polarity opposite to the specific relative polarity to the sense input terminal when the load circuit is closed.
Suitably, the drive means is included in an integrated circuit chip which may also include fault and overload protection means. Such a chip may suitably be Motorola~ UAA
1041 or SGS Thomson~ 9686. It may also be possible to include some or all the blocking means in an integrated circuit chip.
The blocking means may be, for example, diode bridges located firstly between a V+ pin of the integrated circuit and each of the first and second terminals arranged to block negative signal to the positive pin, secondly between a -VCC pin of the integrated circuit and each of the first and second terminals to block positive signal to the negative pin, and thirdly between a sensing pin and each of the first and second terminals to block positive signal to the sensing pin from the one of the first and second terminals that is connected to the DC power source.
An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which:
Figure 1 shows a prior art circuit for a flasher adapted for use only with the polarity as indicated;
Figure 2 shows a modified circuit of Figure 1 for a fixed load flasher switch, adapted, due to an embodiment of the invention, for use with polarity in either direction;
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Figure 3 shows a circuit modified in a similar manner to that of Figure 2 but for a variable load flasher switch;
Figure 4 shows a simplified circuit showing features of the invention.
Figure 1 of the drawings illustrates a circuit diagram of a prior art flasher switch. In fact, the circuit illustrates a two-pin flasher switch as described and claimed in co-pending Canadian Patent Application No. 595,229 hereinbefore referred to. The circuit includes a positive source or connection X and a lamp load L. Positive source X may be connected to the positive terminal of an automotive battery source (not shown). It is to be understood that in accordance with the present invention, switching means (not shown) will be present intermediate of the load L and the flasher switch circuit, and that such switching means may include switches of the 4-way hazard warning light type or of the directional turn signal type. The lamp load L will vary according to the number and types of operative automotive lamps connected in the installed circuit.
With reference to Figure 1 showing a fixed load flasher, positive source X is connected to a relatively low resistance shunt 10. Shunt 10 is connected to both a relay contact 18 and terminal 7 on an integrated circuit 20. Integrated circuit 20 may be of a type readily available to the automotive parts manufacturing industry, such as model number UAA 1041 manufactured by Motorola Semiconductor Products Division of Motorola Limited. All IC pin numbers discussed below correspond to pins 1 to 8 of the Motorola~ UAA 1041 integrated circuit, as would be known to a person skilled in the art. As described herein, integrated circuit 20 may be of a type providing overvoltage protection, fault detection and other protective features.
S ~ ~ J ~
Terminal 7 is a fault detector pin for detection of, for example, a shorted lamp socket. If a shorted lamp socket is present in the circuit, a lower voltage is sensed at this terminal if it is connected as shown and the signal switch operation is prevented. However, if terminal 7 is not connected, the switch will operate as variable load flasher switch. Terminal pin 6 acts as an on-off switch for the fault detector (overcurrent) feature. Where, as shown, terminal 6 is not connected to a positive voltage source, the fault detector feature is in the on-position. Where this feature is not desired, the terminal pin 6 should be connected to a positive voltage source. It is to be understood that such a feature is possible with fixed load flasher switches where a unit will be designed to operate properly only when all of a specified number of lamps are functional. In applications where a variable load flasher switch is desirable, such a fault detection feature is not possible as it is inherently required that all remaining functional lamps be permitted to flash upon activation of the switch. It is necessary that positive source X is connected to the V+ pin 2 on the integrated circuit 20 for proper operation of the integrated clrcult .
In the embodiment shown, source X is also connected to two capacitors 22 and 24 of differing sizes to allow for the avoidance of using a separate ground and hence a third terminal of the device. However, insofar as the present invention is concerned, it is to be understood that the circuit of Figure 1 is merely exemplary of a suitable circuit onto which the present invention may be superimposed. The concept of the present invention may equally be utilized for three-pin devices.
Nevertheless, the operation of the circuit of Figure 1 will be briefly described by way of example. Capacitor 22 is connected to V+ pin 2 and to diode 32 which acts to suppress discharge of capacitor 22 across the lighting circuit, namely, 6 ~ 3 ~ z the load L. Diode 32 is connected to resistor 11 which is in turn connected to sensing terminal pin 8 on the circuit 20.
Pin 8 acts as a sensor for detection of the closure of relay contact 18 through detection of a voltage level. Diode 30 serves a similar purpose to that of diode 32 by acting as a gate to suppress discharge of capacitor 24 across the lighting circuit. As shown, capacitor 24 is connected in series to suppressor diode 30 as previously described and resistor 13 is connected between pin 1 and capacitor 24. Resistor 13 is in turn connected to pin 1 on integrated circuit 20, pin 1 being the -VCC pin for the integrated circuit 20.
Initially, pin 8 senses a negative signal due to direct connection of lamp load L. Such a negative signal at sensing pin 8 allows energization of relay coil connected to pin 3 of integrated circuit 20. Relay coil 40, when energized, closes relay contact 18, allowing a positive signal to pass to pin 8.
Capacitor 26, which in conjunction with resistor 12 functions as a timer circuit, is connected to terminal pin 4 and resistor 12 which is in turn connected to terminal pin 5 of the integrated circuit 20. The flash rate of the flasher switch circuit is a function of the features of the capacitor 26 and resistor 12. The capacitance rating of the capacitor 26 determines the time off of lights operating on the flasher circuit and the corresponding resistance rating of resistor 12 determines the on time of such lights.
The operation of the flasher switch assembly through a complete cycle may be described in generalized terms as follows. Upon activation of a switch, such as a directional turn signal switch or a hazard warning light switch (not shown), a negative voltage is sensed at sensing pin 8. Timing capacitor 26 is charged and once charged to capacity, relay coil 40 is energized, thereby closing contact 18. Upon closing contact 18, reversal in the signal is sensed at terminal 8 causing the capacitor 26 to discharge. A signal ~ ~ ~ c~
through pin 4 or 5 determines when the relay contact is opened.
The circuit may easily be modified to provide a variable load flasher switch by disconnection of pin 7 but, in this case, it is not possible to utilize any overload protection and outage indicator provided in integrated circuits as it is not possible to specify the number of lights that may not be operative at any time.
For the above described circuit, it may be seen that, for proper operation of integrated circuit 20, it is necessary to present a positive voltage at pin 2, a negative voltage at pin 1 and an initial negative voltage at pin 8. In the circuit of Figure 1, if the terminals X and L are reversed, the proper polarity is not presented and the integrated circuit 20 does not operate. Automobiles are, however, inconsistent in the polarity of wiring to supply directional flasher switches.
This may not cause a great deal of difficulty in the installation of original units, but replacement units should preferably be utilizable with wiring of either polarity.
The invention, an embodiment of which is shown in Figures 2 and 3, provides a device suitable for use with wiring of either polarity. Figure 2 shows a device for fixed load operation including shunt 10 connected to pin 7 of the integrated circuit 20 and Figure 3 shows pin 7 disconnected for variable load operation. Figure 4 is a simplified diagram showing only the connections of blocking means to the V+, -VCC
and sensing pins of the integrated circuit 20. Terminals 50 and 52 are shown, replacing terminals X and L of Figure 1.
Terminal 50 may be either positive or negative and terminal 52 may be either positive or negative without affecting operation of the device. This is achieved by the presence of diode bridges Dl, D2, D3, D4, D5 and D7. Diodes D6 and D7 correspond to diodes 30 and 32 in Figure 1 and are so 8 ~ ,f c,~
referenced in Figure 2. Thus, diode D7 carries out a dual function.
Diodes Dl and D7 connect -VCC of integrated circuit 20 to respective terminals 50 and 52.
When terminal 50 is connected to the positive battery terminal of an automobile and terminal 52 is connected to the load, diode D1 will block positive voltage signal reaching -VCC
pin 1. Positive voltage will, however, reach positive pin 2 through diode D2. In this circumstance, terminal 52 will carry the load and will be relatively negative, essentially functioning as a ground. Negative voltage will be blocked from positive pin 2 by diode D3 but will reach -VCC pin 1 by diode D7. On start-up, a relative negative voltage will be received at pin 8 from terminal 52 as is necessary for operation of integrated circuit 20. Thus, for the configuration where terminal 50 is positive and 52 is negative, pin 8 receives the proper signal.
When terminal 50 is connected to the positive battery terminal, a relative negative voltage will initially be received at sensing pin 8 irrespective of the presence of diodes D4 and D5, but it may be seen that diode D5 allows such relative negative signal to reach pin 8.
When terminal 52 is connected to the positive battery terminal and terminal 50 carries the load, diode D7 prevents a positive voltage at -VCC pin 1 while diode D1 does not prevent a negative voltage as a result of the load functioning as a ground. Similarly, diode D3 allows positive voltage at positive pin 2 and negative voltage is blocked through diode D2 .
When terminal 52 is connected to the positive battery terminal, the situation at sensing pin 8 is a little more ., ,. .
complex. Sensing pin 8 requires an initial relative negative voltage to allow pin 3 (not shown on Figure 4 for simplicity) to conduct. In this case, the presence and arrangement of diode D5 blocks the transmission of positive voltage from terminal 52 to pin 8. Special measures are necessary to ensure the initial relative negative voltage necessary at pin 8. As in the prior configuration, this may be provided by means of resistor 15. Positive signal from 52 is transmitted by D3 but, due to resistor 15, relative negative signal is presented at pin 8. Thus pin 3 conducts with resultant closing of relay contacts 18, and pin 8 is made positive through resistor 15 as the positive signal no longer has access to ground. The sensing pin 8 thus operates normally.
The values for the various resistors 11, 15, 12 and 13 is a matter of choice to achieve suitable voltages at the respective pins of the integrated circuit chip 20 and across the various capacitors. This choice will be within the skills of a person skilled in the art and will vary with the circuitry employed.
It may, however, be noted that a device according to the invention may be made suitable for use with 12-volt batteries, as are common in automobiles, and may be readily adapted to use with a twenty-four volt system by the provision of a suitable resistor 15 in the circuitry. The provision of such a resistor is possible whichever of terminals 50 or 52 is the battery terminal.
It is also worth noting that some automobiles are wired utilizing a positive earth from the battery. A device according to the invention may readily be adapted for use in such wiring.
Various designs of flasher switches have been made in the past. Thermal flasher switches incorporating a bi-metal construction designed to be activated upon resistance heating and expansion of metal components continue to be in frequent use. Such units are popular due to relatively low cost of manufacture. They may be of very simple construction, requiring only a connector pin to the electrical supply and a connector pin to the load. The supply may be either of positive or negative polarity. Such switches may be operated with two connection pins, but have frequently been provided with another pole and a third pin to allow for additional services to the automobile driver, such as the provision of an independent dashboard light indicating serviceability of the system. Disadvantages such as temperature sensitivity and limited lifespan make thermal switches less favourable in a wide variety of heavy duty applications such as in trucks.
Flasher switches incorporating single pole, single throw relays have also been used. Again, these devices are relatively robust. Such flasher switches have been designed for operation under either fixed load or variable load conditions.
With the introduction of sophisticated integrated circuits, it became possible to control the operation of a relay through an integrated circuit (IC). Flasher switches utilizing this technology required three pins, since a ground for the IC was necessary. Overload protection and short circuit protection is normally regarded as necessary for such devices. These devices were also strictly operable in circuits of one polarity only. Thus, if such a device were connected into a circuit "back to front", it would not operate.
Nevertheless, such devices have various advantages. These electronic flashers utilizing IC were, in their early embodiment, unsuitable for the replacement of failed devices unless these were of a similar design. One reason for this was the necessity for utilizing three pins in the improved device while the failed devices would be of the two-pin type and hence suitable connections from the new device would not be present. This difficulty was addressed in Canadian Patent Application No. 595,229, filed March 30, 1989, inventor, Rodney Hayden. That patent application described and claimed a directional flasher switch incorporating an IC and designed to operate without a ground so that only two pins are required. The switch of that patent application is, however, dependent on polarity and thus is not suitable for a replacement part unless the wiring into which it is to be incorporated is of proper polarity.
An attempt has now been made to provide a flasher switch utilizing circuit having electronic relay control and which may be tolerant to connection into a circuit of either polarity.
According to the invention, there is provided a flasher switch reversibly operable with a DC power source and a load including: a first terminal adapted for connection to either one of the DC power source and the load; a second terminal adapted for connection to the DC power source when the first terminal is connected to the load and to the load when the first terminal is connected to the DC power source; a relay connected to open and close a load circuit; drive means for the relay having a positive input terminal for positive input connected to each of the first and second terminals, a negative input terminal for negative input connected to each of the first and second terminals, and a sense input terminal connected to each of the first and second terminals, the drive means being adapted to open and close the load circuit in response to signals applied to the sense input terminal; first means to block transmission of negative signal to the positive input terminal; second means to block transmission of positive signal to the negative input terminal; and third means to block transmission of signal other than that of a specific relative polarity to the sense input terminal when the load circuit is open and to present signal of a polarity opposite to the specific relative polarity to the sense input terminal when the load circuit is closed.
Suitably, the drive means is included in an integrated circuit chip which may also include fault and overload protection means. Such a chip may suitably be Motorola~ UAA
1041 or SGS Thomson~ 9686. It may also be possible to include some or all the blocking means in an integrated circuit chip.
The blocking means may be, for example, diode bridges located firstly between a V+ pin of the integrated circuit and each of the first and second terminals arranged to block negative signal to the positive pin, secondly between a -VCC pin of the integrated circuit and each of the first and second terminals to block positive signal to the negative pin, and thirdly between a sensing pin and each of the first and second terminals to block positive signal to the sensing pin from the one of the first and second terminals that is connected to the DC power source.
An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which:
Figure 1 shows a prior art circuit for a flasher adapted for use only with the polarity as indicated;
Figure 2 shows a modified circuit of Figure 1 for a fixed load flasher switch, adapted, due to an embodiment of the invention, for use with polarity in either direction;
l' ;
Figure 3 shows a circuit modified in a similar manner to that of Figure 2 but for a variable load flasher switch;
Figure 4 shows a simplified circuit showing features of the invention.
Figure 1 of the drawings illustrates a circuit diagram of a prior art flasher switch. In fact, the circuit illustrates a two-pin flasher switch as described and claimed in co-pending Canadian Patent Application No. 595,229 hereinbefore referred to. The circuit includes a positive source or connection X and a lamp load L. Positive source X may be connected to the positive terminal of an automotive battery source (not shown). It is to be understood that in accordance with the present invention, switching means (not shown) will be present intermediate of the load L and the flasher switch circuit, and that such switching means may include switches of the 4-way hazard warning light type or of the directional turn signal type. The lamp load L will vary according to the number and types of operative automotive lamps connected in the installed circuit.
With reference to Figure 1 showing a fixed load flasher, positive source X is connected to a relatively low resistance shunt 10. Shunt 10 is connected to both a relay contact 18 and terminal 7 on an integrated circuit 20. Integrated circuit 20 may be of a type readily available to the automotive parts manufacturing industry, such as model number UAA 1041 manufactured by Motorola Semiconductor Products Division of Motorola Limited. All IC pin numbers discussed below correspond to pins 1 to 8 of the Motorola~ UAA 1041 integrated circuit, as would be known to a person skilled in the art. As described herein, integrated circuit 20 may be of a type providing overvoltage protection, fault detection and other protective features.
S ~ ~ J ~
Terminal 7 is a fault detector pin for detection of, for example, a shorted lamp socket. If a shorted lamp socket is present in the circuit, a lower voltage is sensed at this terminal if it is connected as shown and the signal switch operation is prevented. However, if terminal 7 is not connected, the switch will operate as variable load flasher switch. Terminal pin 6 acts as an on-off switch for the fault detector (overcurrent) feature. Where, as shown, terminal 6 is not connected to a positive voltage source, the fault detector feature is in the on-position. Where this feature is not desired, the terminal pin 6 should be connected to a positive voltage source. It is to be understood that such a feature is possible with fixed load flasher switches where a unit will be designed to operate properly only when all of a specified number of lamps are functional. In applications where a variable load flasher switch is desirable, such a fault detection feature is not possible as it is inherently required that all remaining functional lamps be permitted to flash upon activation of the switch. It is necessary that positive source X is connected to the V+ pin 2 on the integrated circuit 20 for proper operation of the integrated clrcult .
In the embodiment shown, source X is also connected to two capacitors 22 and 24 of differing sizes to allow for the avoidance of using a separate ground and hence a third terminal of the device. However, insofar as the present invention is concerned, it is to be understood that the circuit of Figure 1 is merely exemplary of a suitable circuit onto which the present invention may be superimposed. The concept of the present invention may equally be utilized for three-pin devices.
Nevertheless, the operation of the circuit of Figure 1 will be briefly described by way of example. Capacitor 22 is connected to V+ pin 2 and to diode 32 which acts to suppress discharge of capacitor 22 across the lighting circuit, namely, 6 ~ 3 ~ z the load L. Diode 32 is connected to resistor 11 which is in turn connected to sensing terminal pin 8 on the circuit 20.
Pin 8 acts as a sensor for detection of the closure of relay contact 18 through detection of a voltage level. Diode 30 serves a similar purpose to that of diode 32 by acting as a gate to suppress discharge of capacitor 24 across the lighting circuit. As shown, capacitor 24 is connected in series to suppressor diode 30 as previously described and resistor 13 is connected between pin 1 and capacitor 24. Resistor 13 is in turn connected to pin 1 on integrated circuit 20, pin 1 being the -VCC pin for the integrated circuit 20.
Initially, pin 8 senses a negative signal due to direct connection of lamp load L. Such a negative signal at sensing pin 8 allows energization of relay coil connected to pin 3 of integrated circuit 20. Relay coil 40, when energized, closes relay contact 18, allowing a positive signal to pass to pin 8.
Capacitor 26, which in conjunction with resistor 12 functions as a timer circuit, is connected to terminal pin 4 and resistor 12 which is in turn connected to terminal pin 5 of the integrated circuit 20. The flash rate of the flasher switch circuit is a function of the features of the capacitor 26 and resistor 12. The capacitance rating of the capacitor 26 determines the time off of lights operating on the flasher circuit and the corresponding resistance rating of resistor 12 determines the on time of such lights.
The operation of the flasher switch assembly through a complete cycle may be described in generalized terms as follows. Upon activation of a switch, such as a directional turn signal switch or a hazard warning light switch (not shown), a negative voltage is sensed at sensing pin 8. Timing capacitor 26 is charged and once charged to capacity, relay coil 40 is energized, thereby closing contact 18. Upon closing contact 18, reversal in the signal is sensed at terminal 8 causing the capacitor 26 to discharge. A signal ~ ~ ~ c~
through pin 4 or 5 determines when the relay contact is opened.
The circuit may easily be modified to provide a variable load flasher switch by disconnection of pin 7 but, in this case, it is not possible to utilize any overload protection and outage indicator provided in integrated circuits as it is not possible to specify the number of lights that may not be operative at any time.
For the above described circuit, it may be seen that, for proper operation of integrated circuit 20, it is necessary to present a positive voltage at pin 2, a negative voltage at pin 1 and an initial negative voltage at pin 8. In the circuit of Figure 1, if the terminals X and L are reversed, the proper polarity is not presented and the integrated circuit 20 does not operate. Automobiles are, however, inconsistent in the polarity of wiring to supply directional flasher switches.
This may not cause a great deal of difficulty in the installation of original units, but replacement units should preferably be utilizable with wiring of either polarity.
The invention, an embodiment of which is shown in Figures 2 and 3, provides a device suitable for use with wiring of either polarity. Figure 2 shows a device for fixed load operation including shunt 10 connected to pin 7 of the integrated circuit 20 and Figure 3 shows pin 7 disconnected for variable load operation. Figure 4 is a simplified diagram showing only the connections of blocking means to the V+, -VCC
and sensing pins of the integrated circuit 20. Terminals 50 and 52 are shown, replacing terminals X and L of Figure 1.
Terminal 50 may be either positive or negative and terminal 52 may be either positive or negative without affecting operation of the device. This is achieved by the presence of diode bridges Dl, D2, D3, D4, D5 and D7. Diodes D6 and D7 correspond to diodes 30 and 32 in Figure 1 and are so 8 ~ ,f c,~
referenced in Figure 2. Thus, diode D7 carries out a dual function.
Diodes Dl and D7 connect -VCC of integrated circuit 20 to respective terminals 50 and 52.
When terminal 50 is connected to the positive battery terminal of an automobile and terminal 52 is connected to the load, diode D1 will block positive voltage signal reaching -VCC
pin 1. Positive voltage will, however, reach positive pin 2 through diode D2. In this circumstance, terminal 52 will carry the load and will be relatively negative, essentially functioning as a ground. Negative voltage will be blocked from positive pin 2 by diode D3 but will reach -VCC pin 1 by diode D7. On start-up, a relative negative voltage will be received at pin 8 from terminal 52 as is necessary for operation of integrated circuit 20. Thus, for the configuration where terminal 50 is positive and 52 is negative, pin 8 receives the proper signal.
When terminal 50 is connected to the positive battery terminal, a relative negative voltage will initially be received at sensing pin 8 irrespective of the presence of diodes D4 and D5, but it may be seen that diode D5 allows such relative negative signal to reach pin 8.
When terminal 52 is connected to the positive battery terminal and terminal 50 carries the load, diode D7 prevents a positive voltage at -VCC pin 1 while diode D1 does not prevent a negative voltage as a result of the load functioning as a ground. Similarly, diode D3 allows positive voltage at positive pin 2 and negative voltage is blocked through diode D2 .
When terminal 52 is connected to the positive battery terminal, the situation at sensing pin 8 is a little more ., ,. .
complex. Sensing pin 8 requires an initial relative negative voltage to allow pin 3 (not shown on Figure 4 for simplicity) to conduct. In this case, the presence and arrangement of diode D5 blocks the transmission of positive voltage from terminal 52 to pin 8. Special measures are necessary to ensure the initial relative negative voltage necessary at pin 8. As in the prior configuration, this may be provided by means of resistor 15. Positive signal from 52 is transmitted by D3 but, due to resistor 15, relative negative signal is presented at pin 8. Thus pin 3 conducts with resultant closing of relay contacts 18, and pin 8 is made positive through resistor 15 as the positive signal no longer has access to ground. The sensing pin 8 thus operates normally.
The values for the various resistors 11, 15, 12 and 13 is a matter of choice to achieve suitable voltages at the respective pins of the integrated circuit chip 20 and across the various capacitors. This choice will be within the skills of a person skilled in the art and will vary with the circuitry employed.
It may, however, be noted that a device according to the invention may be made suitable for use with 12-volt batteries, as are common in automobiles, and may be readily adapted to use with a twenty-four volt system by the provision of a suitable resistor 15 in the circuitry. The provision of such a resistor is possible whichever of terminals 50 or 52 is the battery terminal.
It is also worth noting that some automobiles are wired utilizing a positive earth from the battery. A device according to the invention may readily be adapted for use in such wiring.
Claims (7)
1. A flasher switch reversibly operable with a DC power source and a load comprising:
a first terminal adapted for connection to either one of the DC power source and the load;
a second terminal adapted for connection to the DC
power source when the first terminal is connected to the load and to the load when the first terminal is connected to the DC power source;
a relay connected to open and close a load circuit;
drive means for the relay having a positive input terminal for positive input connected to each of the first and second terminals, a negative input terminal for negative input connected to each of the first and second terminals and a sense input terminal connected to each of the first and second terminals, the drive means being adapted to open and close the load circuit in response to signals applied to the sense input terminal;
first means to block transmission of negative signal to the positive input terminal;
second means to block transmission of positive signal to the negative input terminal; and third means to block transmission of signal other than that of a specific relative polarity presented to the sense input terminal when the load circuit is open and that of a polarity opposite to the specific relative polarity presented to the sense input terminal when the load circuit is closed.
a first terminal adapted for connection to either one of the DC power source and the load;
a second terminal adapted for connection to the DC
power source when the first terminal is connected to the load and to the load when the first terminal is connected to the DC power source;
a relay connected to open and close a load circuit;
drive means for the relay having a positive input terminal for positive input connected to each of the first and second terminals, a negative input terminal for negative input connected to each of the first and second terminals and a sense input terminal connected to each of the first and second terminals, the drive means being adapted to open and close the load circuit in response to signals applied to the sense input terminal;
first means to block transmission of negative signal to the positive input terminal;
second means to block transmission of positive signal to the negative input terminal; and third means to block transmission of signal other than that of a specific relative polarity presented to the sense input terminal when the load circuit is open and that of a polarity opposite to the specific relative polarity presented to the sense input terminal when the load circuit is closed.
2. A switch as claimed in claim 1, in which the drive means is included in an integrated circuit.
3. A switch as claimed in claim 2, in which the third means includes a resistor connected to present the signal of the specific relative polarity to the sense input terminal.
4. A switch as claimed in claim 3, in which the first means comprises diode bridges connected respectively between the positive input terminal and each of the first and second terminals arranged to block negative signal to the positive input terminal.
5. A switch as claimed in claim 3, in which the second means comprises diode bridges connected respectively between the negative input terminal and each of the first and second terminals to block positive signal to the negative input terminal.
6. A switch as claimed in claim 3, in which the third means comprises diode bridges connected respectively between the sense input terminal and the one of the first and second terminals that is connected to the DC power source to block positive signal to the sense input terminal from the one of the first and second terminals that is connected to the DC power source.
7. A switch as claimed in claim 6, in which a resistor is connected between the one of the first and second terminals that is connected to the DC power source and the sense input terminal, whereby positive signal transmitted to the one of the first and second terminals that is connected to the DC power source is presented to the sense input terminal as relative negative signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2031037 CA2031037C (en) | 1990-11-28 | 1990-11-28 | Flasher switch circuit independent of polarity of supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2031037 CA2031037C (en) | 1990-11-28 | 1990-11-28 | Flasher switch circuit independent of polarity of supply |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2031037A1 CA2031037A1 (en) | 1992-05-29 |
| CA2031037C true CA2031037C (en) | 1999-05-11 |
Family
ID=4146548
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2031037 Expired - Fee Related CA2031037C (en) | 1990-11-28 | 1990-11-28 | Flasher switch circuit independent of polarity of supply |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2031037C (en) |
-
1990
- 1990-11-28 CA CA 2031037 patent/CA2031037C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2031037A1 (en) | 1992-05-29 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |