Specific Switch needed

I am looking for a switch for a 12v push switch to be activated when a door is opened and again when closed, it need to make contact halfway down its travel when depressed and off when fully depressed, then on release it needs to be momentarily on then off when fully released. I have searched but only seem to find momentary switches that stay on when fully depressed, any links would be great, thanks in advance

This task is always done electronically and may be referred as a "frequency doubler" as you want a pulse on each edge. But you want the threshold to be defined as the halfway point. Typical with all mechanical switches is to have backlash to reduce the chance of contact bounce. Naturally, this also results in hysteresis so that the transitions in each direction are skewed from the mean threshold. But I suspect, this is acceptable.

So to produce a pulse on each transition of either polarity, we might use both inputs of an CMOS XOR or XNOR gate with an RC delay to define the pulse duration like 1/10th second. Then mix that CMOS pulse output with an audible tone to drive a piezo buzzer or simply drive a buzzer. The buzzer currents are higher on magnetic types, so I would suggest the higher pitch piezo types.

simulation for you.

this is simply for a door light so doesnt need to be elaborate, I just need a momentary on switch when opening and closing to trigger the circuit I am using

Use a changeover switch that does not have a "snap" action.

Connect the normally open and normally closed contacts together for one side of the circuit & use the common as the other.

That gives the inverse of what you are asking for, a switch closed at either extreme and open in the middle - but to trigger something electronic, ground one side and add a pull-up resistor to the other and you have a signal than will go "high" part way through the movement.


Or, two separate switches with the plungers adjusted to different lengths or in different positions, so they operate at different angles of the door travel.

Wire them in series to break the circuit, so one breaks as the door gets near fully closed and the other as it's wider open. The two would both be on only at the middle of the movement range.

Other than that, you probably need to make one yourself.
eg. a small magnet in a tube with a spring behind it and a plastic pushrod in front, with a magnetic reed switch attached to the side of the tube so it operates only at the bid point of the magnet movement.

Or the switch on an arm mounted to the door frame & the magnet set in the top of the door; a bit like an old style shop bell that sounded as the door opened.

A rotary switch arranged with a linkage so it turned with the door movement?
Use one or two contacts that close part way through the total travel range.

You can buy the electrical switch version of a shop door bell device!
eg.

They mount to the frame just above the door at a suitable distance from the hinge, so the door lifts the "cam" briefly as it opens or closes.

paulsm1uk said:

I am looking for a switch for a 12v push switch to be activated when a door is opened and again when closed, it need to make contact halfway down its travel when depressed and off when fully depressed, then on release it needs to be momentarily on then off when fully released. I have searched but only seem to find momentary switches that stay on when fully depressed, any links would be great, thanks in advance

Click to expand...

Why a push button? It seems you'd want an angle sensor to sense how far the door is opened.