enclosuremountswitchestoggle switch
I need to mount a mini toggle or rocker switch to the outside surface of a box. For various reasons I cannot drill a hole, so the entire switch needs to be freestanding or glued to the surface. (There is a small hole for the wires to go into the box, but that's it.)
I remember seeing self-contained switches with nice plastic back covers, but I can't find any such components on the market. Can anyone recommend a good way to cover up the exposed contacts and even provide a nice flat surface?
If it's a "reed switch" you're talking about, they do indeed exist in SPDT form, though they're not as common as SPST N.O.. Also in SPST N.C. (normally closed) form. For example:
If you want to reverse the action of a SPST N.O. switch, you may be able to do something like this:
In the case of the BJT, make Rx about 10-20 times RL. In the case of the MOSFET, make Rx a few K ohms.
simulate this circuit – Schematic created using CircuitLab
Your diagram shows SPDT, so that's what you need. SPST isn't going to work.
The peak current through the switch will be the same as if you connected the relay coil directly to the 12V supply without the capacitor in place. (The capacitor merely causes the current to decay down to zero from this peak value.)
Therefore, if your 12V relay has a coil resistance of 400 Ω, the peak current will be 12V/400Ω = 0.030A.
With a 220 µF capacitor, the relay will activate for roughly 50-100 ms each time the toggle switch changes state. The exact value depends on the holding-current requirements of the relay.
Best Answer
Use heat-shrink tubing. Use a small size that will shrink to a snug fit on the wires and terminals, and a larger size to cover the body of the switch, and extend over the wires.
If the switch carries 120 or 240 VAC, I would prefer to add a box to contain the switch and wires, but the heat-shrink technique should be OK (not ideal) for low voltage.