With suicide doors, my biggest fear is driving off with a door ajar. I have this mental picture of rocketing (hyperbole in a 2cv) along the Queensway only to have a door open with a loud spang, bend into a pretzel, and act like a huge rudder forcing me into the path of an oncoming 40-tonne transport. So door latch locks with warning lights and an alarm are a must.
In previous articles, I mentioned that I have a wreck with suicide doors and I recovered the suicide door latches from it. Turns out that the latches have a little locking lever that you can use to lock the door closed while driving. Great stuff!! The only problem is, how do you remember to lock the door? Hey, I am now 67 and can just manage to walk and chew gum! So, I came up with this idea to modify the locking lever to operate a microswitch and connect it to warning lights and a chime.
Here are some pictures to show what I came up with.
The first picture shows the door latch mounted on a plate welded to the inside of the door frame. I drilled a hole straight through the locking lever, and epoxied a shortened 1 1-1/2 finishing nail through the hole. The finishing nail passes through a curved slot milled into the latch mounting plate and is used to operate a microswitch fastened to the other side of the mounting plate.
The next picture shows the other side of the mounting plate and the microswitch with the latch locking lever off (the door latch is free to operate).
The last picture shows the microswitch with the interlock on (the door latch cannot be operated).
Here is a schematic of an alarm circuit I dreamed up. The way it is supposed to work is at the end of the schematic.