The articles discusses an automatic door mechanism circuit that responds to the ambient light conditions by keeping the door open during day time and closed during night. Here the application is used for operating a hen house door. The idea was requested by Mr. Gavin Sweet
Hi I have a project that I am starting to investigate and was wondering if you had any ideas
The project is to make an automatic door for a hen house, I would like it to be controlled by dawn/dusk to run a 12v motor to open the door then reaching a limit switch to then reverse motor direction when it is dark returning the door down to a second limit switch placed at the bottom of the door (I was also Hoping to put a delay on the door closure of Upto 30 mins)
There are many designs for a timer version of this circuit but this would mean periodic adjustments to the programmable timer.
I hope you can point me in the right direction
The Circuit Design
The requested dawn dusk hen house door operator circuit may be witnessed in the above diagram and understood with the help of the following points.
Two 555 IC stages can be seen the proposed design.
The IC1 stage is wired as light activated switch using an LDR as the sensor.
The relay associated with IC1 is held deactivated during day time and vice versa.
IC2 is configured as a set/reset latch flip flop or bistable stage wherein the relay associated with this IC stays activated when SW1 is in the depressed position and deactivated when SW2 is in a pushed ON state.
Let's assume it's day time and the door being fully open, and the door mechanism keeping the SW1 switch pushed ON.
In the above scenario, the IC1 DPDT relay can be assumed to be in the N/C positions, while the IC2 relay in N/O position.
IC2 relay being in the N/O position cuts off the negative supply to the DPDT relay making sure that the motor in this state stays shut off and tightly locked keeping SW1 pressed and ON.
Now, as day light begins to fade and dusk arrives, the LDR senses this and toggles IC1 pin3 low, actuating the DPDT relay whose contacts now change positions towards their respective N/O points.
The above changeover immediately switches ON the motor which starts moving the door mechanism until its fully closed. In the course it releases SW1 rendering IC2 in a standby position.
When the closing procedure ends, SW2 which is positioned at the the other end of the door mechanism responds to the closing of the door pressure resets the IC2 such that its relay now chnages from N/O to N/C. This action instantly cuts off the other negative line to the N/O contacts of the DPDT.aking sure that the motor shuts off again and stays in that position until dawn sets in.
The 2200u capacitor and R3 may be appropriately tweaked for getting a delayed response from IC1 after dawn or dusk transitions are sensed by the LDR