PROGRAMMABLE AUTOMATIC BLIND OPENER

The blind opener consists of a DC motor that controls the blind pulley via a custom-made gear system. The blind is operated by a control panel, allowing you to either open or close the blind or to set the automatic timing function. A RTC (Real time clock) is used to add the automatic timing function of the blind opener. The start and stop point of the blind is controlled by coloured strips at the top and bottom of the blind, these are detected by a Sensor

STEP 1: OVERVIEW

Basically, the blind opener works by using a DC motor to drive a custom made gear. The cord of the blind fits around this gear and as it turns, the blind is pulled up or down, depending on its direction of rotation.

MOTOR::

The motor's direction of rotation is controlled by connecting it to two relays, these are used to reverse the polarity of the supplied voltage, thus changing the motor's direction. In essence, we are using an H-Bridge.

Control Panel::

The control panel is laser cut from Acrylic sheet and incorporates a 20x4 LCD (Liquid Crystal Display) and four buttons, which are used to program the blind opener.

Blind Direction and State:

The directional movement of the blind is controlled by the use of red and green strips of paper. These strips also act as a trigger to stop the movement of the blind. They are positioned at the top (red) and bottom (green) of the blind. A sensor monitors the blind for the presence of these strips, and when detected, depending on colour it sets the direction of the blind (either up or down) for its next movement.

Arduino (x2):

The reason for using two Arduinos is that one Arduino can be completely dedicated

 to monitoring the colour sensor operation.

Main Arduino:

The main Arduino is responsible for driving the LCD, RTC, Motor and checking the other Arduino. The Arduino controls the motor by using an electrically isolated relay module which is required as the motor runs off 12v, whereas the Arduino runs of 5v. To simplify the design and wiring, a voltage booster is used to convert the 5v from the Arduino's power pins to the 12v that the motor needs. We can use a boost converter as opposed to an external power supply because the motor only requires 150mA to run which is quite a small amount of current compared to other motors.

Secondary Arduino:

The secondary Arduino is used to monitor the sensor. It is dedicated to this function and requires only a small bit of code. It is not interrupted by other functions that may cause it to miss-detect the strips on the blind. This Arduino tells the main Arduino where the blind is by pulling one of two signal wires high. One signal wire is pulled high when the blind is fully up, and the other is pulled high when the blind is fully down.