JPH021038Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an indicator circuit for an overhead projector that is equipped with a switchable main lamp and a spare lamp, and displays the status of the spare lamp externally using an indicator lamp.

The applicant previously proposed switching to an overhead projector (hereinafter referred to as OHP) in order to eliminate the inconvenience of having to interrupt the progress of a meeting, class, etc. when the light source lamp unexpectedly burns out and projection becomes impossible. It is equipped with a main lamp and a spare lamp that can be used, and the pilot also checks whether the spare lamp is disconnected or the spare lamp is forgotten to be installed, that is, whether the spare lamp is in a state where it can be used when the main lamp is used. We proposed a lamp switching device (Utility Model Application Publication No. 104497/1983) that uses lamps to display information externally and guarantees that there will be no interruption to meetings, etc.

By the way, in such a device, in order to simplify the circuit for turning on or off the pilot lamp, when the spare lamp is in a normal state, that is,
The pilot lamp lights up when the spare lamp is set and can be energized, but when there is an abnormality with the spare lamp, i.e., the spare lamp has been forgotten to be installed, or the lamp is disconnected and is not conducting. It was a device that would turn off the pilot lamp when the aircraft was in use.

However, from the user's point of view, it is clear and reliable that the indicator indicating an abnormality in the spare lamp lights up only when an abnormality occurs to prompt the user to replace or install the spare lamp, and it serves the original purpose of warning. be.

The present invention has been developed in response to such a request, and its purpose is to quickly configure the indicator lamp to turn off when the spare lamp is normal, and turn on when an abnormality occurs.
To provide an indicator circuit that further improves reliability when using an OHP and can be implemented with a simple circuit.

In order to achieve this purpose, the present inventor has provided a main lamp and a spare lamp that can be used interchangeably,
Applying an OHP indicator circuit that externally displays the status of the spare lamp with an indicator lamp,
Its main feature is that when switching to the main lamp, the indicator lamp is turned off by the conducting state of the spare lamp, and the indicator lamp is turned on by the non-conducting state of the spare lamp.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

Figure 1 is a mechanical configuration diagram showing an example of an OHP lamp switching device to which the present invention is applied, and Figures 2 to 4.
The figures are OHP indicator circuit diagrams according to the present invention, showing first to third embodiments, respectively.

First, in order to clarify the present invention, an exemplary lamp switching device will be described with reference to FIG.

1 is a light source box, and this light source box 1
A support plate 2 is installed horizontally at approximately the center of the support plate 2, and a holding member 3 having a horizontal channel-shaped cross section is attached to one end of the support plate 2.
are fixed so that both ends thereof are in contact with the inner surface of the box 1. A long hole (not shown) is formed in the plate surface of the holding member 3 in the longitudinal direction, and a plate 4 having a substantially similar cross-sectional shape is slidably mounted thereon. Two light source lamps 5 and 6 are attached spaced apart in the longitudinal direction of this plate 4, and these light source lamps 5 and 6 are attached to the holding member 3.
The long hole faces the center of Box 1. Further, a knob 7 is provided at one end of the plate 4 protruding from the opening of the box 1 (not shown), and by operating this knob 8, the plate 4 is slid within the holding member 3. A plate spring or the like is interposed between the holding member 3 and the plate 4 so that the plate 4 comes into elastic contact with the holding member 3 with moderation.

On the other hand, a micro switch 8 is installed on the support plate 2 to switch the circuits of the light source lamps 5 and 6 according to the sliding of the plate 4, and a condensing reflector 9 is installed directly below the position where the light source lamps are used. are arranged.

Further, a display section 10 is formed on the front surface of the light source box 1, and an indicator lamp 11 is provided on this display section 10 to indicate the status of the light source lamp that is not in use, that is, a spare lamp. A light intensity adjustment dial 12 for the light source lamps 5 and 6 is mounted on the side. Note that the lamp in use among the light source lamps 5 and 6 functions as a main lamp, and the other functions as a spare lamp. This mechanism shows one example to which the present invention can be applied, and can be applied to other types of lamp switching devices.

Next, an indicator circuit connected to the indicator lamp 11 will be explained with reference to FIGS. 2 to 4.

FIG. 2 relates to the first embodiment, with reference numerals 13a, 13
b is a power supply terminal to which a predetermined alternating current voltage or direct current voltage can be applied. The movable contact 8a of the microswitch 8 is connected to the power terminal 13a, one end of the light source lamps 5 and 6 is connected to the fixed contacts 8b and 8c, respectively, and the other end is connected to the power terminal 13b.

On the other hand, 14 is an indicator circuit according to the present invention. The circuit connects a resistor R ₁ and a diode D ₁ in parallel, and connects the cathode side to one end of the light source lamp 5, that is, the fixed contact 8b, and connects a resistor R ₂ and a diode D ₂ in parallel, and connects this cathode side to one end of the light source lamp 6. It is connected to one end, that is, the fixed contact 8c.
The anode sides of diodes D ₁ and D ₂ and one end of resistor R ₃ are connected in common, and the other end of this resistor R ₃ is connected to indicator lamp 1 using a light emitting diode or the like.
The lamp 11 is connected in series to one end of the lamp 11, and the other end of the lamp 11 is connected to the power supply terminal 13b. A diode _D3 is connected in parallel to this lamp 11 with its anode side facing the power supply terminal 13b. The size of each resistance is R ₁ , R ₂ ,
R ₃ >>Z _L1 , Z _L2 (Z _L1 , Z _L2 : each impedance of the light source lamps 5 and 6) shall be satisfied.

The function of the indicator circuit 14 having the above structure will be explained first. When the micro switch 8 is switched to the fixed contact 8b side, the light source lamp 5 becomes the main lamp, and the light source lamp 6 becomes a spare lamp. If the required alternating current voltage is applied between the power supply terminals 13a and 13b, the light source lamp 5 lights up. In this state, if the light source lamp 6, which is a spare lamp, is not disconnected and is in a conductive state, the current will be reduced by applying a positive voltage. Resistor R ₁ , diode D ₂ , light source lamp 6
Flows through the path of , and when negative voltage is applied, diode D ₃ ,
It flows through the path of resistor R ₃ and diode D ₁ . In this case, the potential V _A at point A is V _A ≒ V _F ≒ 0.6 ~ when a positive voltage is applied.
The voltage is 0.7V (V _F : diode forward voltage), which is less than the forward voltage V _L (≒2V) of the indicator lamp 11 (light emitting diode), so the lamp 11 does not light up. Also, current flows through the light source lamp 6.
R ₁ >>Z Lamp 6 does not light up due to _L2 .

Next, if the light source lamp 6 is disconnected or not conductive, a positive voltage is applied and the current flows through the resistors R ₁ , R ₃ ,
Flow lamp 11 in the path of indicator lamp 11
lights up, and when a negative voltage is applied, diode D ₃ , resistor R ₃ ,
The flow lamp 11 does not light up in the path of the diode _D1 . However, the AC voltage of commercial power supply is 50Hz or
Since the frequency is 60Hz, the lamp 11 appears to be lit all the time.

Note that this circuit 14 has a similar function even when a DC voltage is applied. In this case, power terminal 1
Although a positive voltage is applied to the 3a side, a negative voltage is not applied, so the diode _D3 for reverse bias protection becomes unnecessary. Also, since the circuit has symmetry, the micro switch 8 is switched to the fixed contact 8c side, and the light source lamp 6 is switched to the fixed contact 8c side.
It functions similarly when the light source lamp 5 is used as a main lamp and the light source lamp 5 is used as a spare lamp.

Next, a second embodiment will be described with reference to FIG. The difference from the first embodiment is that the micro switch 8 is constructed as a changeover switch 15 having two interlocking circuits and two contacts, and the first switch 16 and the second
It has switch 17. And each switch 16,
17 movable contacts 16a, 17a are connected to the power terminal 13a
and one fixed contact 16b of the first switch.
is connected to the light source lamp 5, and the other fixed contact 16c is connected to the second
It is commonly connected to one fixed contact 17b of the switch 17. Further, the other fixed contact 17c of the second switch 17 is connected to the light source lamp 6. On the other hand, a resistor R ₁ in parallel with the diodes D ₁ and D ₂ shown in the first embodiment
and R ₂ are not needed, instead each diode D ₁ and
The anode side of D ₂ and the fixed contact 16 of the switch
A resistor _R4 is connected between C (or 17b). Other than these, the structure is the same as that of the first embodiment, and the same parts as in FIG. 2 are given the same numbers to clarify the structure. The size of each resistance is R ₃ , R ₄ ≫ _{Z L1} , Z _L2
The following conditions shall be met. In FIG. 3, the portion indicated by the two-dot chain line indicates the indicator circuit 18.

To explain the function of the indicator circuit 18 having the above configuration, first, the changeover switch 15
Movable contacts 16a, 17 of each switch 16, 17
When a is switched to the fixed contacts 16b, 17b side, the light source lamp 5 is lit. If the light source lamp 6 is in a conductive state, the resistor R ₄ and the diode
D ₂ , the circuit of the light source lamp 6 is energized, but neither the indicator lamp 11 nor the light source lamp 6 lights up due to the relationship between V _B (potential at point B) < V _L and R ₄ >> Z _L2 .

On the other hand, if the light source lamp 6 is in a non-conducting state, the resistance
The circuit consisting of R ₄ , resistor R ₃ , and indicator lamp 11 is energized, and indicator lamp 11 lights up. Note that this indicator circuit 18 can also be applied to both alternating current and direct current, and in the case of direct current application, a diode D ₃ is used.
is not necessary. Further, the circuit is symmetrical, and when the changeover switch 15 is switched to the other side, the light source lamp 6 functions as a main lamp, and the light source lamp 5 functions as a spare lamp.

Next, a third embodiment will be described with reference to FIG. This embodiment differs from the first and second embodiments in that a relay is used. That is,
Indicator circuit 14 in FIG. 2 showing the first embodiment
Relay 19 is used instead. relay coil 1
Both terminals of the relay switch 9x are connected between the fixed contacts 8b and 8c of the micro switch 8, and the movable contact 19ya of the relay switch 19y, which is activated by the excitation of the relay coil 19x, is connected to the power terminal 1.
3a, and one fixed contact 19yc is connected to one end of an indicator lamp 11, such as a pilot lamp, and the other end is connected to the power supply terminal 13b. The other fixed contact 19yb of this relay switch 19y is not connected. In addition, Z _R ≫Z _L1 , Z _L2
It is assumed that the following condition (Z _R : impedance of the relay coil 19x) is satisfied. Indicator circuit 20 with this relay 19 and indicator lamp 11
It consists of

To explain the function of the indicator circuit 20, when the micro switch 8 is switched to the fixed contact 8b side, the light source lamp 5 lights up as the main lamp, while the relay coil 19x and the light source lamp 6 are energized, and the energization is stopped. If the relay switch 19y is in the state, the relay switch 19y is the unconnected fixed contact 19.
It has been switched to the yb side and the indicator lamp 11 does not light up. On the other hand, in this state, if the light source lamp 6 is in a non-conducting state due to a disconnection or the like, the relay coil 1
There is no excitation of 9x, and relay switch 19
y is switched to the fixed contact 19yc side, and the indicator lamp 11 is energized and lit. Note that in the third embodiment, a DC power source is applied.

In each of these embodiments, when switching to the main lamp side, if the spare lamp is normal, the indicator lamp 11 lights up, but there are circumstances such as forgetting to install the spare lamp, disconnection of the spare lamp, etc. that prevent it from being used normally. When the indicator lamp 11 lights up, the purpose of the present invention is achieved.

Therefore, each embodiment is illustrative, and other circuit changes that do not depart from the gist are permitted within the scope of the present invention.

As is clear from the above explanation, the present invention
OHP indicator circuit is in spare lamp status,
In particular, since the indicator lamp is turned on when there is an abnormality, the abnormality can be recognized clearly and reliably, and reliability when using the OHP can be improved. Furthermore, it can be provided as an OHP indicator circuit with a relatively simple circuit configuration and can be implemented at low cost, and has high practical value.

[Brief explanation of the drawing]

FIG. 1 is a mechanical configuration diagram of a lamp switching device for an overhead projector to which the present invention is applied, and FIGS. 2 to 4 show first to third embodiments of the overhead projector according to the present invention. It is an indicator circuit diagram of Ekta. In the drawings, 5 and 6 are light source lamps, 11 is an indicator lamp, and 14, 15, and 20 are indicator circuits.

Claims (1)

[Scope of utility model registration request] In the indicator circuit of an overhead projector that is equipped with a switchable main lamp and a spare lamp, and displays the status of the spare lamp externally using an indicator lamp, when the main lamp is switched, the indicator lamp is activated depending on the normal status of the spare lamp. An indicator circuit for an overhead projector, characterized in that the indicator lamp is turned off and turned on when a spare lamp is in a non-conductive state.