Hi, this is my first post 
I do not have a great deal of knowledge with electronic circuits other than the basics so please be patient if my terminology is not quite right
Ok now to my project, basically I've got a few old projectors (Hitachi ED-A101s) two of which are suffering a common fault which is a mechanical failure within the mirror motor gearbox assy. the failure is very common and as such I'm looking to bypass the mirror motor so that the mirror can simply be opened by hand. The perfect hack would be to modify the firmware but reverse engineering lines assembly code would be a nightmarish task.
Now the problem and project requirements..
The problem is that the projector monitors the mirror using a changeover switch triggered by a cam this switch (via some resistors) returns a signal to the SoC telling it what position the mirror is in. The movement is also appears to be timed in the firmware so if it's too fast or too slow reaching a position it fails and shuts down. As such we can't simply unplug the motor :-/
From the service manual schematics it appears that the cam / switch works as follows
Endpoint 1 - return output ~1mv
Travelling / Moving - return output 2.43v
Endpoint 2 - return output 1.59v
My idea is to take the motor input (+12vdc or -12vdc depending on direction) use it as a trigger input to a circuit that emulates the correct cam switch response allowing us to use our projectors without these dreaded gearbox failures, they are used primarily by our community group who are a non profit group so don't have the funds to replace the gearboxes every time they fail.
The circuit would need to have a method of adjusting the time delay between endpoints (emulating motor travel time) e.g. :-
+12v
Endpoint 1 (1mv) --> moving 8s (2.43v) --> endpoint 2 (1.59v)
-12v
Endpoint 1 (1.59v) --> moving 8s (2.43v) --> endpoint 2 (1mv)
Any ideas and or advice, would be greatfuly received.
I do not have a great deal of knowledge with electronic circuits other than the basics so please be patient if my terminology is not quite right Ok now to my project, basically I've got a few old projectors (Hitachi ED-A101s) two of which are suffering a common fault which is a mechanical failure within the mirror motor gearbox assy. the failure is very common and as such I'm looking to bypass the mirror motor so that the mirror can simply be opened by hand. The perfect hack would be to modify the firmware but reverse engineering lines assembly code would be a nightmarish task.
Now the problem and project requirements..
The problem is that the projector monitors the mirror using a changeover switch triggered by a cam this switch (via some resistors) returns a signal to the SoC telling it what position the mirror is in. The movement is also appears to be timed in the firmware so if it's too fast or too slow reaching a position it fails and shuts down. As such we can't simply unplug the motor :-/
From the service manual schematics it appears that the cam / switch works as follows
Endpoint 1 - return output ~1mv
Travelling / Moving - return output 2.43v
Endpoint 2 - return output 1.59v
My idea is to take the motor input (+12vdc or -12vdc depending on direction) use it as a trigger input to a circuit that emulates the correct cam switch response allowing us to use our projectors without these dreaded gearbox failures, they are used primarily by our community group who are a non profit group so don't have the funds to replace the gearboxes every time they fail.
The circuit would need to have a method of adjusting the time delay between endpoints (emulating motor travel time) e.g. :-
+12v
Endpoint 1 (1mv) --> moving 8s (2.43v) --> endpoint 2 (1.59v)
-12v
Endpoint 1 (1.59v) --> moving 8s (2.43v) --> endpoint 2 (1mv)
Any ideas and or advice, would be greatfuly received.
