Hi - I'm looking for a very small and low profile DPST momentary tactile switch. Problem is - I can't find *any*. Naturally a DPDT would be ok as well. Best I've been able to find is some DPDTs that stick up maybe 15mm. I'm looking for something of the ~8x8x5mm variety. Does such a beast exist? Thanks,
You reminded me that I do want them to be NO, which I forgot to mention in my OP. I'm sure it would be possible to add in some additional circuitry to make a SPST work - but it would be complicated. The problem is that this button will be acting as a reset. It will be grounded and then each pole will be connected to the active low disable input of two power regulators. (low = off, high/high impedance = on). Thus when the button is pressed all regulated power on the board is gone, so driving a relay or other supporting logic gets tricky. I'd have to use the unregulated power.
It seems the standard package for a low profile tactile switch has 4 contacts - it just seems a natural to me that there'd be some DPSTs... Thanks,
Can you use two BSS123? Sources to GND, drains to the respective regulator control pins, gates tied together, resistor from gate node to ground and then the button sends unregulated VCC onto the gate node for the shut-off function. If the unregulated VCC is higher than the gate breakdown you'd need one more resistor to create a voltage divider. The BSS123 comes in SOT23 which should be small enough.
If Digikey doesn't have any they might really be unobtanium.
Normally you'd design around the fact that tac switches are single pole NO. But if you must have a 2 pole one, its not difficult. The black conductive material is a thin layer on the underside of the switch. Simply cut out a strip across the middle. You now have 2 conductive pads. Design the PCB pads accordingly, and you have a 2 pole switch.
The one issue you need to watch for is that it might in some cases enable a user to squish the rubber over to short the 2 poles together. Attention to detail.
Thought about that as well. But it will be a bear in production because you'd have to glue the bar on top or engage in some elaborate molding to hold it in place. Glueing will cause grief such as the glue running into the switch and so on.
Then there is the issue of veered and incomplete button pressing. That can cause one regulator to stop while the other keeps cranking.