Simple relay circuit help

[skazz]

I have a DPDT latching relay, and I'm wondering about the simplest way to throw it with a SPST switch. Any ideas would be very appreciated.

[XCVG]

Like this, I think:

[Gordon1]

That's ok, but in this case I think it would be better to switch the negative.

[nitro2k01]

That's ok, but in this case I think it would be better to switch the negative.

Why? In this very simple circuit, it makes absolutely no difference whatsoever.

[XCVG]

That's ok, but in this case I think it would be better to switch the negative.

With such a small load it doesn't really matter.

[skazz]

Thanks for the diagram. Someone showed me an elegant solution with a couple diodes, so it looks like it's covered for now. Thanks guys.

[XCVG]

Thanks for the diagram. Someone showed me an elegant solution with a couple diodes, so it looks like it's covered for now. Thanks guys.

Diodes? Where would they go in the circuit?

[timmeh87]

Relays give you a high voltage spike when you turn them off, it will fry any sensitive electronics without the diode.

[XCVG]

Ah. Never knew that. Makes sense though.

[Mario]

So where do the diodes go? I had an auto A/V switcher in my portable that turned the screen on and off when I plugged in the AV cable. The N64 would reset whenever I unplugged it (turning the screen back on, the relay off). Where do the diodes go?

[timmeh87]

jfgi

put it across the relay coil so that it normally would do nothing but it lets the inductance drain through the diode when you switch it off. The associated discharge goes against the normal flow of current.

[nitro2k01]

For clarity:

The diode alongside the relay coil is necessary to avoid sparks and/or interference. The one between the switch and the relay is optional, but adds more protection. The diodes should be 1n400x (1n4001, 1n4002, 1n4003, 1n4004 should all work)
If you're using a 9V battery to power the relay, and nothing but the relay, you only need the first diode.