Friday, April 12, 2013

Automatic Curtain Opener

This circuit can be used with a timer clock to open and shut curtains or (vertical) Venetian blinds. The curtain or blind is pushed by using  an electrical motor with a discount gearbox suited to the keep watch over mechanism of the curtain or blind. This circuit is good for giving your home an occupied look when you are away on vacation or for any different reason. In the author’s house, this association has provided a few 12 monthss of trouble-free carrier on quite a few home windows fitted  with Venetian blinds. 

The unique design was once a easy relay circuit with pushbuttons for opening and shutting and reed switches acting as restrict switches. The mechanical force is equipped by using a small DC motor with a reduction gearbox and pulley (all from Conrad Electronics).  It used to be later modified to work robotically with a timer clock. The timer operates a small  230-VAC (or 120-VAC) relay with a changeover contact. Thanks to the two timers, the motor stops after just a few 2nds if probably the most reed switches is overlooked as a consequence of a mechanical defect. 

Circuit diagram :

Automatic Curtain Opener Circuit Diagram
The circuit works as follows (see Figure 1). In the quiescent state, relays RE1–RE3 are de-energised and the motor is ceaseped. Open the blind: 

When the timer clock applies power to the 230-V (120-V) relay RE3, the voltage on the junction of C1 and R1 goes high. IC1 (a 555)  then receives a set off pulse on pin 2, which lead tos its output (pin 3) to go High and energise RE1, which in turn result ins the motor to begin running. When the magnet reaches reed  swap S1 (‘Open’), the 555 is reset. If the reed  switch does no longer function for some purpose, the relay is de-energised anyways when the  monostable times out (time extend = 1.1 RC;  roughly 5 seconds). Close the blind:
The timer clock cast offs power from RE3, which causes a trigger pulse to be utilized to the opposite 555 timer (IC2) via R5 and C4. Now the motor starts operating within the other direction. The rest of the operation is similar as described above for opening the blind. Diodes D2 and D5 stop the outputs of the 555 ICs from being pulled bad when the relay is de-energised, which could differentwise result in the timer ICs to malfunction. 

All  elements  of  the  mechanical  power  come from Conrad Electronics [2]: a motor with a reduction gearbox (type RB32, order quantity 221936) and a pulley (V-belt pulley, order number 238341) on the output shaft. An O-ring is suited to the pulley to provide  sufficient friction with the force chain of the Venetian blind. The magnet for actuating the  reed swapes is a rod magnet with a hole within the middle (order number 503659), and the chain of the Venetian blind is fed thru this hole.

Author : Ton Smits  - Copyright : Elekto