connecting AC and DC lines using a single connector ?

Hi, aman. I'm assuming you're talking about a standard DB-25 connector. like the ones used for RS-232. This is a bad idea for several reasons.

First, these connectors are basically meant to conduct low current, low voltage signals. The pins are optimistically rated for 1 amp, which I suppose is OK, at least at the beginning. However, as you have multiple insertion/extraction cycles, the connection tends to get resistive. As it does, the heat increases as the square of the voltage drop across the connector, and you've got plenty of volts to turn into heat. You can easily melt the thermoplastic around the pins with a resistive connection, with predictably disastrous results. And a fuse probably won't protect you until after the connector sockets have melted into each other. Actually, the fuse will respect this by politely refusing to blow until the hot pin socket has come into contact with a ground-referenced logic signal, smoking your electronics. It will probably chuckle to itself while this is happening, though, and not in a nice way.

Next, if there's any chance of the connector being unplugged while live, the arc right next to your low voltage signals will want to cause problems. Along these lines, you should also be aware that the soft metals used in the connector pins/sockets are not made to take the heat of the switching arc. You could easily weld them together. And in the event of a line voltage fault condition, overcurrent could damage the pin/socket long before the fuse goes.

You want to look at the possibility of a wire breaking in the connector shell, too. Do you want a line voltage wire with a squib of wire at the end floating around in your shell? Got a metal shell? Got insurance?

The problems get magnified if you're using a cable with multi-conductor wire. The current going through the line will lead to inductive coupling (will probably smoke your stuff with an overcurrent condition). The proximity of the wires in the cable will cause capacitive coupling (will probably smoke your stuff if there's a line surge). And most conductors in these cables aren't specified for line voltage. There will be a leakage current you'll have to deal with. Any or all of these will kill digital logic, or worse, cause intermittent glitches which will drive you nuts.

By the way, you're not planning on having a male pin sticking out with

I think you've got a start on understanding in how many ways this is a bad idea.

Sorry to be the bearer of bad news. Just put in another connector, or a terminal block, or just about anything else. It's not worth it.

Good luck. Chris

If you are dealing with 120 VAC, I would be worried about the voltage rating of the connector - I don't think most small multi-contact connectors will be rated to handle that voltage.

Generally, I try to keep line voltage well isolated from signal and low voltage DC supply wiring.

Although I agree with the previous posts about the lack of experience, I will note that there are connectors specifially designed for the purpose you want (although they aren't particularly cheap).

The usual culprits (AMP/Tyco, Molex, FCI, Samtec, JST et al) all make wire to board connectors that have some high voltage / high current contacts in the same shell as low voltage/low power contacts, with appropriate ratings on the pins (including pin to pin breakdowns and arc ratings).

I suggest you look at those (and other manufacturers I obviously missed) websites to see if there's something suitable and then see if it's available from your favourite mail order supplier.

Cheers

PeteS

If you need to ask this question you do not understand enough electricity to be designing boards with 120volts AC on them. You should be using a Wallwart to supply a lower voltage or if this thing is to switch mains power you need some help from a professional designer.

Sorry to be harsh but electricity travels at the speed of light and kills just as fast.