Isolating charger socket

[mowgli]

But doing that leaves one of socket pins live. I'm trying to leave the socket grounded to avoid electrolysis. It's possibly the world's worst schematic but I've attached a picture to give you the general idea of where I'm going. Use the plug to pull the base low. Your thoughts?

Edit: That's a PNP transistor

[bogan]

But doing that leaves one of socket pins live. I'm trying to leave the socket grounded to avoid electrolysis. It's possibly the world's worst schematic but I've attached a picture to give you the general idea of where I'm going. Use the plug to pull the base low. Your thoughts?

Edit: That's a PNP transistor

hmm, she's getting well complicated now (would need a base resistor as well), is there not an easier non-circuitry solutions, such as plated terminals, or a cover for the plug?

[mowgli]

Complicated? Nah, would probably fit neatly on the end of the relay in a bit of resin. You're right regarding the base resistor. My bad.

I could stick the socket under the seat but then that's not as tidy as "pull up, plug in and walk away". Plated terminals could work. The previous socket had a cover. I think that lead to the condensation.

[bogan]

you may find that a pnp will also put positive voltage on the wire (base)

[mowgli]

you may find that a pnp will also put positive voltage on the wire (base)

Hmmm, of course it does
It's been a fun exercise but I'm beginning to think an electronic solution is a bit beyond me. Thanks for the help.

[bogan]

Hmmm, of course it does
It's been a fun exercise but I'm beginning to think an electronic solution is a bit beyond me. Thanks for the help.

looks like a quality job though!

Think the problem is you need to pass a signal without using any voltage (current signaling requires less voltage but there must be some), so you're going up against the laws of physics

[mowgli]

By inverting the low input and driving an NPN I can reduce the voltage at the pins to quite low (see diagram) but that's about the best I can do. Damn laws of physics

Edit: T1 and T2 are both BC547

[NinjaNanna]

its all very foggy to me - so don't crucify me if I'm wrong but I think your problem may be that your 2k4 base resistor is too big.

Base current for the BC178 is 50mA (100mA max) your resistor only allows 5mA to flow meaning the transistor is hardly turning on.

Try a resistor 220ohm resistor or 150ohm

[mowgli]

its all very foggy to me - so don't crucify me if I'm wrong but I think your problem may be that your 2k4 base resistor is too big.

Base current for the BC178 is 50mA (100mA max) your resistor only allows 5mA to flow meaning the transistor is hardly turning on.

Try a resistor 220ohm resistor or 150ohm

My bad! The schematic is not up to date. The relay only draws 30mA so the transistor doesn't need to turn on fully (I think). I ended up using a PN200 and a 2k2 base resistor. All very approximate when you're scraping the bottom of the components drawer.

Anyway it works in the sense that it switches the relay when plugged in. It still fails to reduce the potential between pins in the unplugged socket. Hence my later schematic using an inverter. Again all very approximate

[mossy1200]

Just a thought.If your current plug has copper terminals it will oxidise reguardless of power at socket or not.You need to have silver terminal ends on the socket.

[mowgli]

Just a thought.If your current plug has copper terminals it will oxidise reguardless of power at socket or not.You need to have silver terminal ends on the socket.

It's been fun but I think this is the answer. A marine grade plug and socket will no doubt sort this out.

[bogan]

It's been fun but I think this is the answer. A marine grade plug and socket will no doubt sort this out.

yup, sometimes the most fun projects are the one that dont do bugger all!