JPH06100046B2 - Electric blind descent height setting device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a descent height setting device for an electric blind,
In particular, the present invention relates to an electric blind descent height setting device capable of easily designating and canceling the descent position of the blind.

[Prior Art] A conventionally proposed device for setting a descent height of an electric blind is composed of a reduction mechanism that applies rotation of a lifting shaft and a cam. That is, the rotation speed of the elevating shaft is reduced to open and close contacts such as a micro switch linked with a cam or the like to stop the electric motor. When changing the descent height, adjust the screwed bolt of the cam that turns on and off the micro switch in the speed reduction mechanism, which causes the motor to stop early or late, resulting in The descent height was adjusted by controlling the energization time. In other words, the energization time of the electric motor is changed by changing the position of the cam.

[Problems to be Solved by the Invention] However, in such a conventional method for setting the descent height by the electric blind, when the descent height is established by adjusting the position of the cam, the electric blind is always required. It was necessary to install the on the window frame to lower the blind, attach it to the blind depending on the height of the window frame, and adjust the cut-and-dry method while operating the electric blind on site. For this reason, there is a drawback that it takes a lot of time and labor to adjust the attachment to the window frame. In addition, the friction state and position of the cam change due to long-term use and changes over time, and the descending height changes, and it is necessary to manually adjust the descending height each time, and the cam, gear, or screw bolt However, the main purpose of the present invention is to make adjustment unnecessary and to lower the blind to the set position. It is an object of the present invention to provide a descent height setting device for an electric blind.

[Means for Solving the Problems] The above object of the present invention is to provide the commanding means such as a controller with the descending position height setting of the electric blind, and to set the descending position height from the commanding means such as the controller. Can be achieved by

That is, the descent height setting device of the electric blind according to the present invention, the command means for commanding the rising or lowering of the blind, a plurality of blades connected by a string-like member, the electric motor and the rotation of the electric motor. A head box that houses a drum that rotates to wind or unwind the string-like member to raise and lower the blind, and a lower limit position that is provided in the command means and that sets the lower limit position of the blind to fall to an arbitrary position. Lower limit position setting means for setting, a coupling means for transmitting and receiving a signal relating to the lower limit position set between the command means and the head box, and a pulse signal for generating a pulse signal according to the rotation of the drum. Counts the pulse signals generated by the generating means and the pulse signal generating means in response to the rising or falling command from the commanding means and sets the lower limit position. Storage means for rewritably storing the pulse count value at an arbitrary position set by the step, and counting the generated pulse signal, and whether or not the count value matches the value set by the lower limit position setting means In accordance with the determining means and the descending command, the electric motor is rotated to rewind the string-like member by the drum to lower the blind, and the count value matches the value set by the lower limit position setting means. And a control means for stopping the electric motor in response to the determination.

[Operation] The descent height setting device for an electric blind according to the present invention is
The descent height is set from the command means, the pulse signal generated according to the rotation of the drum when the blind is lowered is counted, and the count value corresponding to the descent height of the blind is the lower limit set in advance. Since the descent of the blind is stopped if it coincides with the position, complicated adjustment work can be eliminated, and the descent position of the blind can be set from the command means in correspondence with an arbitrary window frame.

[Embodiment of the Invention] As means for solving the conventional problems, for example, a head box for accommodating a blind lifting device, a command means for commanding the raising or processing of the blind, and a head box An electric blind that is provided below and includes a plurality of blades that are connected by a string-shaped member. The blind is provided inside the head box and rotates according to the rotation of the electric motor to wind or unwind the string-shaped member. A drum for raising and lowering, a pulse signal generating means for generating a pulse signal according to the rotation of the drum, and a lower limit position setting means using a dip switch capable of setting a lower limit position of the blind to an arbitrary value, Discrimination for counting generated pulse signals and discriminating whether or not the counted value coincides with the value set by the lower limit position setting means. Means, and the electric motor is rotated in response to the descending command to rewind the string-like member by the drum to descend the blind, and it is determined that the count value matches the value set by the lower limit position setting means. Accordingly, it may be configured by a control unit that stops the electric motor.

However, in the above-described lower limit position setting means for the electric blind, the lower limit setting switch is provided in the control unit built in the head box, and the lower limit of the lowering of the blind is set by the combination of these switches. For this setting, the switch combination is appropriately selected at the factory according to the height of the window to be installed, and it is adjusted to the height to the window. However, if the window height is set incorrectly or the blind lower limit setting switch is set incorrectly, the blind will not be able to reach the bottom of the window frame after it is attached to the window, and a gap will be created at the bottom of the window frame. However, problems such as loosening of the entire blind occur.
In order to correct this, it is necessary to change the setting of the lower limit setting switch and set it again at the installation site so that it is located at the height of the installed window.

However, the lower limit setting switch is provided in the control unit in the head box. Therefore, the workability of re-setting the lower limit setting switch is extremely poor because the headbox is located above the window, etc., and the work efficiency is significantly reduced at the site where many blinds are installed such as offices and conference rooms. . In addition, after installing blinds, if you follow other objects such as potted plants in the lower part of the window frame, in order to prevent the lower part of the blinds from hitting these when lowering the blinds, the descending state of the blinds every time you lower it. It is necessary to stop the descent of the blind while watching, or reset the lower limit setting switch as described above. However, it is generally necessary to ask the construction company that installed the blinds to reset this setting.

Summarizing the above problems, the above-mentioned electric blind lowering position setting device has the following problems.

(I) After installing the blind on the window or the like, it is not possible to easily change the lower limit setting switch provided in the control unit in the head box because the work efficiency in construction is extremely poor.

(Ii) It is necessary to increase the number of combinations of the lower limit switches in order to make the range of the lower limit setting more detailed, which increases the number of the lower limit switches, resulting in an increase in cost. Moreover, the setting operation becomes complicated.

Therefore, in the present invention, the above-mentioned problems are solved by setting the height of the lowered position of the electric blind as follows.

First, with reference to FIG. 2 and FIG. 3, an external configuration of one embodiment of the present invention will be described. Referring to FIG. 2, the conventional electric blind is a head box 15 in which a slat 13 and a device for vertically driving the slat 13 are housed.
And a controller 2 for controlling the upper and lower sides of the slat 13, and a connection cord 20 for connecting the controller and the head box. The head box 15 is a lifting unit 6, 7, 8 for raising and lowering the slats 13 by hoisting and lowering the ladder cord 11, a geared motor 4 for rotating the lifting unit, and a control unit for controlling the rotation of the motor. 3 and an elevating shaft 12 for transmitting the rotational force from the motor to each elevating unit.

The controller 2 includes a raising switch 21 for raising the slats 13, a stop switch 22 for stopping the movement of the slats, and a lowering switch 2 for lowering the slats 13.
3. It includes an open switch 24 for opening the slat and a close switch 25 for closing the slat. The power cord 1 and the controller 2 are connected to the control unit 3. The control unit 3 includes a microcomputer, a power supply unit, and the like. A geared motor 4 including an electric motor and a reduction gear is connected to the control unit 3. The rotation shaft of the geared motor 4 is connected to the lifting shaft 12 via the coupling 5. The lifting shaft 12 includes lifting units 6, 7 and 8
Are connected. Sensors and fault switches (not shown) built in these lifting units 6, 7 and 8
The upper limit switch 16 is connected to the control unit 3 by the wiring member 9. The wiring material 9 also includes wiring to the geared motor 4 and a connection cord 20 to the controller 2. The lifting units 6 and 8 include a winding drum 37 and a ladder drum 39.
And the lifting unit 7 includes only the ladder drum 39.

One end of the lifting tape 10 (which may be a string-like one) is fixed to the winding drum 37.
The other end of the lifting tape 10 has holes 13 for a plurality of slats 13.
It penetrates through a and is fixed to the bottom rail 14. The take-up drum 37 winds or rewinds the lifting tape 10 in accordance with the rotation of the elevating shaft 12, and slats the slats.
Raise and lower 13 and bottom rail 14. Further, one end of the ladder cord 11 is fixed to the ladder drum 39, and the other end of the ladder cord 11 is fixed to the bottom rail 14.

This ladder cord 11 is, for example, 50 mm, 25 mm of slats 13.
Or two 11a, 11b1 with a space corresponding to the width of 15mm
It is composed as a set, these two ladder cords 11
The a and 11b are connected at intervals corresponding to the pitch p of the slats 13, for example, in the form of a ladder with horizontal cords 11c. The slats 13 are inserted and held in a ladder-shaped space composed of ladder cords 11a and 11b and lateral cords 11c. Then, the ladder drum 39 rotates with the rotation of the elevating shaft 12, and controls the opening degree of the slats. The bottom rail 14 functions as a weight for lowering the blind and as a weight for preventing the blind from swaying due to wind or the like after the lowering.

The control unit 3, the geared motor 4, and the lifting units 6, 7, and 8 are covered by a head box 15 that constitutes an outer box. An upper limit switch 16 is provided below the head box 15, and the upper limit switch 16 is pressed by the slats 13 to operate when the blind is wound, and detects the upper limit position. The upper limit switch 16 may be composed of an electronic switch such as an optical sensor.

FIG. 4 is a schematic block diagram of an embodiment of the present invention.
Next, with reference to FIG. 4, an electrical configuration of an embodiment of the present invention will be described. AC power is input to the power transformer 31 via the power cord 1. The power transformer 31 stabilizes the low voltage by stepping down the input AC power supply.
32 to supply the power required for the control unit 3 and the geared moder 4. Microcomputer (MP
(Referred to as U) 34 is connected to the motor drive circuit 33,
In response to a command from 34, the geared motor 4 is controlled in forward rotation, reverse rotation or brake mode.

Here, the brake mode is to short-circuit the input terminal of the geared motor 4 via the motor drive circuit 33,
By thus short-circuiting the input terminals of the geared motor 4, the geared motor 4 can be braked. That is, for example, when mechanical force is applied to the geared motor 4 such as inertia caused by the descent of the blind or when the blind is strongly pulled in the direction in which it is artificially lowered, the geared motor 4 operates on the principle of the DC generator. Will generate a back electromotive force. Therefore, by short-circuiting between the input terminals, a current for causing this rotation to be blocked, that is, a reverse rotation, flows, and the geared motor 4 is stopped. A voltage detection circuit 35 is connected to the MPU 34. The voltage detection circuit 35 detects the voltage of the power supply Vcc supplied to the control unit 3. That is, the voltage detection circuit 35 monitors the voltage supplied from the power cord 1 on the low voltage side via the transformer 31.

The MPU 34 includes RAMA and RAMB for setting the descent position of the electric blind, which will be described later. The RAMA is a part that always counts the intermittent signal from the photo interrupter 38 described later and calculates the count number to store the blind height from the upper limit position. RAMB is a part for storing the descent position height of the blind input from the controller.

The obstacle switch 36 is built in the elevating units 6 and 8. As an example of trouble, when the operation of descending is stopped due to hitting an obstacle or the like while the blind is descending, the geared motor 4 moves in the descending direction. When the rotation is continued, the lifting tape 10 loosens, and when this continues, the lifting tape 10 is removed from the winding drum 37.
However, if the blind is raised next time, the lifting tape 10 cannot be wound up, resulting in a serious failure.

In order to prevent this, loosening of the lifting tape 10 is detected as a conventional technique by a mechanical switch or an optical or magnetic sensor, and the detection output is input to the MPU 34, and a geared motor is supplied via the motor drive circuit 33. I am trying to stop 4. This sets the motor drive circuit 33 to the brake mode. Further, the MPU 34 reverses the geared motor 4 for an arbitrary time and winds up the blind to loosen the lifting tape 10, and then stops the geared motor 4.

The take-up drum 37 takes up or rewinds the lifting tape 10 in accordance with the rotation of the geared motor 4, and raises or lowers the blind.
Includes Guides 371 and 372. A slit 373 is formed around the guide 371, for example. A disc may be attached to the other part of the elevating shaft 12 separately from the winding drum 37 to form a slit in the disc, so that the elevating shaft 12 rotates or the motor shaft of the geared motor 4 rotates. Since the same effect can be obtained by detecting, the mounting position and method are not limited.

A photo interrupter 38 is provided in association with the guide 371 of the winding drum 37. The photo interrupter 38 optically detects the connection / disconnection of the slit 373 formed in the guide 372 of the winding drum 37, converts the rotation of the elevating shaft 12 into an electric signal, and inputs the electric signal into the MPU 30. That is, the MPU 34 can know the amount of lifting or lowering of the lifting tape 10 by the rotation of the winding drum 37 by an electric signal. As described above, one end of the ladder cord 11 is fixed to the ladder drum 39, and the rotation of the ladder drum 39 changes the angle of the slats 13 to change the input amount of outside light to achieve an appropriate brightness in the room. Or turn off external light.

The ladder drum 39 is fitted in a frictional state via a drum shaft 40 that penetrates the lifting shaft 12. The elevating shaft 12 and the drum shaft 40 rotate integrally (synchronously), but when the ladder drum 39 rotates almost half a turn, the rotation of the ladder drum 39 is stopped by a protrusion (not shown) provided by the head box 15 or the like. Then, it slips on the drum shaft 40 and runs idle. Further, when the elevating shaft 12 is reversed, the ladder drum 39 is also reversed in the same manner, but similarly to the above description, it hits a protrusion such as the head box 15 and spins idle. The slat 13 is rotated by the half rotation of the ladder drum 39, and the angle of the slat 13 is changed. That is, the slat 13 changes from a state in which it is slanted and closed on the indoor side to a horizontal state and is opened, and then a state in which it is slanted and closed to the outdoor side. When the elevating shaft 12 rotates in the direction opposite to that described above, the rotation of the slats 13 is reversed. That is, the state in which the outdoor side is tilted and closed is changed to the horizontal state and the state is opened, and the indoor side is tilted and closed.

A slit 391 for detecting the rotation of the ladder drum 39 is formed at one end of the ladder drum 39. The slit 391 is formed at an angle corresponding to almost half rotation of the ladder drum 39, and a photo interrupter 41 is provided to detect the position of the slit 391. The photo interrupter 41 detects the position of the slit 391, converts it into an electric signal, and gives it to the MPU 34. The MPU 34 responds to this electric signal by changing the angle of the ladder drum 39, that is, the slat.
You can know 13 angles. Lower limit position setting switch 42
Is for setting the lower limit position when the blind is lowered, and is composed of four switches in this embodiment.

The switches 21 to 25, the clock generation circuit 43 and the reset circuit 44 of the controller 2 are connected to the MPU 34.

FIG. 1 is a flow chart for explaining a specific operation of one embodiment of the present invention.

Next, the specific operation of the embodiment of the present invention will be described with reference to FIGS. When the power cord 1 is energized, the AC power source is converted into a low voltage by the power transformer 31 and supplied to the stabilized power source 32. The stabilized power supply generates a stable variable power supply Vcc necessary for the control unit and a power supply V _M for driving the geared motor 4. First, when raising the blind, the raising switch 21 provided in the controller 2 is operated. The MPU 34 receives the signal from the raising switch 21 and gives an intermittent signal to the motor drive circuit 33 in order to close the slat 13.

In response, the motor drive circuit 33 intermittently rotates the geared motor 4. When the geared motor 4 is rotated intermittently, this rotational force is transmitted via the coupling 5 to the lifting shaft.
Rotate 12 intermittently. With the rotation of the lifting shaft 12, the winding drum 37 and the ladder drum 39 are rotated via the drum shaft 40. Due to the intermittent rotation, the rudder drum 39 eventually rotates slowly and the rudder cord 11
On the other hand, if, for example, the side of the ladder cord 11b is wound up, the pair of ladder cords 11a is lowered. That is, as the ladder drum 39 rotates in the direction of the arrow in FIG. 3, the ladder cord 11b side goes up and the 11a side goes down. As a result, the slat 13 rotates in the direction of the arrow and is in the closed state.

The ladder drum 39 rotates, the slit 391 provided in the ladder drum 39 interrupts the output signal of the photo interrupter 41, and a pulse signal is given to the MPU 34. MPU34
When the ladder drum 39 is further rotated, that is, the slats 13 are gradually closed, the pulse signals are sequentially counted. When the ladder drum 39 rotates until the slats 13 are completely closed, a protrusion (not shown) provided on the ladder drum 39 hits the protrusion 45 shown in FIG. 3 and the ladder drum 39 idles. Therefore, the photo interrupter 41
The pulse signal from is not given to MPU34. In response, MPU 34 determines that slat 13 is closed.
Further, the MPU 34 counts the number of pulses of the pulse signal output from the photo interrupter 41 after the raising switch 21 is operated, and stores the counted value as a movement angle of the slat 13 in a memory (not shown).

Next, when the pulse signal from the photo interrupter 41 is no longer given to the MPU 34, a continuous winding signal is given to the motor drive circuit 33. In response, the motor drive circuit 33 changes the geared motor 4 from intermittent rotation to continuous rotation, and shifts to the blind winding operation.

That is, as the geared motor 4 continuously rotates, the winding drum 37 continuously rotates, and the lifting tape 10 is rotated.
To wind up. The other end of the lifting tape 10 is a bottom rail
Since it is fixed to 14, the slat 13 gradually rises from the bottom. To stop the rising of the blind, the stop switch 22 provided in the controller 2 is operated.
The MPU 34 gives a stop signal to the motor drive circuit 33 in response to a command from the stop switch 22. Depending on the motor drive circuit
33 stops the geared motor 4. At this time, the motor drive circuit 33 short-circuits the input terminal of the geared motor 4 and brakes the geared motor 4 to stop it. Since this is a well-known technique, its detailed description is omitted.

Next, as described above, the slat 1 stored in the MPU34
In order to return to the angular position of 3, the MPU 34 gives a reverse rotation intermittent signal to the motor drive circuit 33 to reverse the ladder drum 39 in the direction opposite to the arrow shown in FIG. As a result, the ladder cord 11 performs the opposite operation to that described above, and the slat 13 rotates in the direction opposite to the arrow and is opened.
At the same time, the MPU 34 counts the pulse signal from the photo interrupter 41, and if it matches the count value input when rising,
U34 gives a signal for stopping the geared moat 4 to the motor drive circuit 33 to stop the geared motor 4. As a result, the blind is automatically adjusted to the angle of the slat 13 before stopping and ascending.

The operation when lowering the blind is performed by the controller 2
This is done by operating the descent switch 23 provided on the. The descent of the blind is performed by performing an operation substantially opposite to the above-described ascent. When the stop switch 22 of the controller 2 is operated, the geared motor 4 is stopped at that point and the blind is stopped. Further, the angle of the slat 13 is automatically adjusted to the angle before descending in the same manner as described above.

Next, a method of setting the descent height of the blind will be described. The setting of the descent height of the blind according to the present invention is performed using the stop and descent switch provided in the conventional controller. Not only the setting of the lowered position but also the setting by the dip switch described in the related art may be used together.

FIG. 1 is a flow chart showing a procedure for setting a lower limit position of an electric blind according to the present invention. This will be described below with reference to FIG. When the raising switch 21 is input, the MPU 34 rotates the geared motor 4 via the drive circuit 33, and the blind rises. If there is no input from the controller 2, the blind rises until the upper limit switch 16 is pushed by the slat 13, and if there is an input from the upper limit switch 16, the MPU 34
Receives this input, and stops the geared motor 4 via the motor drive circuit 33. The blinds stop. At this time, the blind is at the uppermost limit, and the upper limit switch 16
At the same time as the input of, the MPU 34 initializes the height data and sets this position as the upper limit value. Next, when the descent switch 23 of the controller 2 is input, the blind starts descent. At the same time as the descent starts, the photo interrupter 38 transmits an intermittent signal to the MPU by the slit 373 provided in the winding drum 37.
Enter in 34. The MPU 34 knows the number of revolutions of the winding drum 37 by counting this intermittent signal, and knows the descent amount (height) of the blind. Visually confirm that the blind height has dropped to the desired lower limit, and
Input the stop switch 22 provided at. Upon receiving this input, the MPU 34 stops the geared motor 4 (brake mode) via the motor drive circuit 33. The blinds stop. At this time, the MPU 34 stores the count number of the intermittent signal from the photo interrupter 38 in the RAMA. After confirming that the blind is at the desired lower limit, the stop switch 22 provided on the controller 2 is first pressed, and then the descent switch 23 is simultaneously input for an arbitrarily set time (for example, 2 seconds). In response to this input, the current blind position is set to the lower limit, and the count number is stored in the RAMB as the lower limit value A. Here, the stop switch 22 is first input for the following reason. If other switches (up / down, angle opening / closing) are input, the blinds immediately operate according to the input. To prevent this, if the stop switch 22 is first input and then the descent switch is input, the blind will not operate. While the stop switch 22 is input, the blind does not operate even if there is input from another switch. (Geared motor 4 remains stopped). In this state, the raising switch of the controller 2
When 21 is operated to raise the blind, the MPU 34 counts the intermittent signal from the photo interrupter 38, always calculates the height from the upper limit position, and stores the count number of the intermittent signal from the upper limit position in RAMA. Operate the stop switch 22,
When the blind is stopped and then the descent switch 23 is operated to lower the blind, the intermittent signal from the photo interrupter 38 is counted from the position and calculated, and the height from the upper limit position is sequentially stored in the RAMA. Intermittent signals corresponding to the height from the upper limit position are counted, RAMA and RAMB are compared, and if this value matches the minimum limit value A, the microcomputer
34 determines that the blind has dropped to the lowest limit, and stops the geared motor 4 (brake mode) via the drive circuit 33. The blind is stopped, and the blind is stopped at the lowest position by the simultaneous operation of the stop switch 22 and the descent switch 23 from the controller 2.

The controller 2 has a stop switch 22 and a descent switch 23.
The lower limit position set by the simultaneous operation of is simultaneously released by the stop switch 22 and the raising switch 21. That is, RAMB is erased. Also in this case, similarly to the above, the stop switch 22 is first input, and then the raising switch 21 is input. The lower limit at this time depends on the setting position of the lower limit switch 42. Also, regarding the blade angle, if the open switch 24 and the stop switch 22 for adjusting the angle provided in the controller 2 are input at the same time, the current blade angle will be stored, and the close switch 25 and the stop switch 22 will be displayed at the same time. By inputting it, the memory of the blade angle can be erased, and it is possible to always set a constant blade angle after going up and down. However, when changing the lower limit value of the blind, the controller 2 stops the switch 22 as described above. RA that stores the lower limit value A by inputting the up and down switch 21 at the same time for any time
After MB is erased and the blind is raised or lowered to the changed position, the stop switch 22 and the descent switch 23 of the controller 2 may be simultaneously input. The position of the blind is newly stored in the RAMB, this value becomes a new lower limit value A, and when the blind is subsequently lowered, if this value lower limit value A and RAMA match, the blind stops as the lower limit. It will be.

[Effects of the Invention] As described above, according to the present invention, since the blind descending position height setting means is provided in the command means such as the controller, the command means such as the controller separated from the head box provided at a high place. It is possible to set the descent position height of the blind depending on the position. Therefore, even after the electric blind is attached to the window frame, the descent height of the blind can be easily adjusted. Moreover, there is an effect that it is possible to easily change even after setting once. As a result, workability during construction and workability during blind assembly are significantly improved, omission or combination of lower limit switches can be reduced, complexity of lower limit switch settings and setting errors can be prevented, and cost is also reduced. There is also an effect such as possible.

[Brief description of drawings]

FIG. 1 is a flow chart for explaining a specific operation of one embodiment of the present invention. FIG. 2 is a diagram showing an outline of an embodiment of the present invention. FIG. 3 is a view showing a main part of a blind winding mechanism. FIG. 4 is a schematic block diagram of an embodiment of the present invention. In the figure, 2 is a controller, 3 is a control unit, 4 is a geared motor, 6, 7 and 8 are lifting units, 10 is a lifting tape, 11 is a ladder cord, 12 is a lifting shaft, 13 is a slat, 14 is a bottom rail, 33 is a motor drive circuit, 34 is a microcomputer, 37 is a take-up drum, 38 and 41 are photointerrupters, 39 is a ladder drum, and 42 is a lower limit position setting switch.

Claims (1)

[Claims] 1. An electric blind that raises and lowers a blind according to the rotation of an electric motor, a command means for commanding an up or down movement of the blind, and a plurality of blades connected by a string-shaped member, Rotating according to the rotation of the electric motor and the electric motor,
A head box that houses a drum for winding or unwinding the string-shaped member to move up and down the blind; and a connecting means for connecting the head box and the command means, Means and a lower limit position setting means for setting the lower limit position for setting the lower limit position for lowering the blind to an arbitrary position; and the command means and the head box provided in the connecting means. And a coupling means for transmitting and receiving a signal relating to the set lower limit position, pulse signal generating means provided in the head box for generating a pulse signal according to rotation of the drum, and the command The lower limit position setting means for counting the pulse signals generated from the pulse signal generating means in response to an ascending or descending command from the means. Therefore, the storage means for rewritably storing the set pulse count value at the set position, the pulse signal generated from the pulse signal generation means is counted, and the count value is the value set by the lower limit position setting means. And a judgment means for judging whether or not the judgment result is matched, and the electric motor is rotated to rewind the string-like member by the drum to lower the blind in response to the descending command from the commanding means. A descent height setting device for an electric blind, comprising: a control unit that stops the electric motor when it is determined that the count value matches the value set and stored by the lower limit position setting unit.