High-voltage DB25 switch

I’m looking for a DB25 switch that can handle up to 300 V (this is for a scientific application, not just a printer or anything like that). I called up the manufacturer of this one and they told me it can’t take voltage that high. I assume this would be the same for most of these switches? Any ideas where I might look?

That sounds pretty specialized to me. Do you need a large quantity, or just one? It might be easier to build it yourself if you need just one. I assume the device that’s using 300V DB25 was designed to do that? Maybe the manufacturer knows of a source?

I’m always leery of using standardized connectors like this in a non-standard application, especially when it would destroy any normal device using that connector if accidentally attached. If I had the choice, I’d use some other kind of connector.

It’s to switch between two different microscope heads (to the same controller). I don’t really need it, it’s mostly for convenience’s sake (avoid having to screw and unscrew the cables each time I switch, which is somewhat frequently). I asked the manufacturer and they didn’t know anything in particular, just that the wiring must be suitable for 300V. I probably wouldn’t bother building one if there isn’t one available off the shelf.

How many cycles does it have to withstand?
I’d bet that the manual switch from Black Box will work, they just won’t spec it at that voltage.
It also might be a bit of a safety hazard, since I’m sure they aren’t HiPot testing them.
Still, if you only need it to last for 100 actuations, they are cheap enough to try.

By “how many cycles”, if you mean how many times it has to be switched, then I’m not sure, but yeah 100 is probably ballpark. Not inclined to take the safety risk on something that hasn’t been tested…

My question would be what kind of current are you going to switch?

DB25 isn’t standardized though. Even on PCs, it’s been used for both parallel and serial ports. In other types of electronic devices, it’s used in all kinds of one-off applications.

I too would bet it would work, especially if you turn off the power to the equipment before operating the switch (which sounds like the case).

However, if it fails, it has the potential to damage the equipment, and void its warranty as well. I’d only risk it if the equipment weren’t expensive or irreplaceable.

That’s a rather oddball application for a D Subminiature connector. My main concern would be that I doubt any manufacturer of the connectors themselves rates the connector insulation for a working voltage that high. However, given that you seem to have a device with that connector and it hasn’t failed…

I’d look for a switch that uses individual wires between the connectors and the switch, rather than one that uses ribbon cable or a circuit board. This may mean looking for a used one at a ham / computer swap meet. I’d also look for one with a plastic case, and if there was any metal (for example, front or back panels) I’d check it carefully myself to make sure the metal isn’t connected to any of the connector pins. Next, make sure it switches all 25 pins (some of these switches make the assumption that they’re controlling printers, and connect some pins together or omit some entirely. Last, I’d only activate the switch when everything connected to it is powered off.

A little poking around, and d-sub connectors can handle a heck of a lot more than we would have guessed. ITT Canon invented the format and they’re rated for 7.5 amps at up to 1000 volts.

However, the Milspecfor them cites a dielectric breakdown of anywhere from 400 - 1000 volts, depending on type, humidity and altitude.

Personally, knowing how close those pins are and the necessarily thin insulation on wires that will fit into the connectors, I’m barely comfortable with putting 50 volts on those things.

Given the replies in the thread, looks like it’s probably not a good idea – this is a very expensive piece of equipment, so I think I’ll just stick with switching the cables out by hand. Thanks all.