|Off-delay box for video projector|
|Provide a timer before the main power is shut off from the video projector.|
Proper utilization of the video projectors that have been installed in AIT classrooms and meeting rooms requires that the projector are disconnected from the main power not before the projectors have been allowed to cool off.
If the main power is disconnected too early, before the fans have stopped running, the lamp is still hot and may blow off.
If the main power is not disconnected while the projector is unused, some electronic circuit in the power supply of the projector will wear out and after one year the projector takes very long time to turn on.
The proper procedure to turn off the projector is:
The ten minutes delay is not applicable for classroom: after the class is finished, people will simply leave the room and if they have to turn off the main power, it must be without waiting any delay. This box is designed to apply the 10 minutes delay after the off button has been pressed.
The box is built around two 10 amp. magnetic contactors and one Telemecanique RE7RM 11BU Off-delay timer.
The first contactor is building the on/off function, when the contactor is on, the indictator lamp is on and the command Z2/Y1 of the delay is closed.
After Z2/Y1 is open, the delay contactor 15/18 will remain closed for the given time (adjustable from 0.5 to 300 seconds).
The second contactor is only a power line for the video projector: the delay contactor should supply up to 8 amp. while the projector typical power is 2.5 amp.; but the second contactor is just a security against over power.
A 10 amp. circuit breaker at the top of the diagram provides protection for the box.
|Contact us: Olivier Nicole||Last update: Nov 2007|