Automatically opening and closing a door

Question

I'm working on an automatic door that runs like this:

1. Receives an input trigger, probably a voltage input
2. DC motor runs in one direction for x seconds to open the door
3. Same DC motor reverses direction for x seconds to close the door
4. Standby for another trigger

The challenge here is that I can't use any microcontrollers (I'm too reliant on those things) and that everything is automated. I've done some research, so I've figured that I can control the motor direction with a H-bridge IC like an L298N, but I'm pretty confused with the timing control.

So far, I've found capacitor and 555 timing control circuits, but they are timing to ON and OFF circuits, which I'm not sure how to fit in here. I've also found a couple of time delay relays, but I don't know how those work.

Any help would be appreciated, thanks!

Answer 1

I've built a circuit in Proteus VSM for you. The circuit consists of 3 blocks:

1) A Monostable Multivibrator for managing trigger signals and generating enable signals:

img source: http://www.electronics-tutorials.ws

2) An astable multivibrator for managing open- and close-durations:

img source: http://www.electronics-tutorials.ws

NOTE: If you want both durations to be equal then use the following:

img source: http://www.electronics-tutorials.ws

3) Motor Driver:

Final circuit (Click for full view):

First block is a monostable multivibrator with trigger input and "ENABLE/STOP" output. The output goes directly to the second block's ENABLE/RESET input and the motor driver's ENABLE input. The duration of ENABLE signal is the sum of on- and off-durations: \$T = 1.1 \cdot R5 \cdot C4 = 1.1 \cdot 27k \cdot 330\mu F = 9.8s\$

Second block is an astable multivibrator with equal on- and off-durations: \$T_{on} = T_{off} = 0.693 \cdot R1 \cdot C2 = 0.693 \cdot 20k \cdot 330\mu F = 5s\$.

Third block is a 2-way motor driver. Setting IN1=1 and IN2=0 forces the motor to turn on one direction; likewise setting IN1=0 and IN2=1 forces the motor to turn on the reverse direction.

Here's the Proteus VSM simulation file: http://www.filedropper.com/m_5