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Driving side lights from head lights
nstrug - 7/9/08 at 06:00 PM

I have separate switches for sidelights and headlights and I would like the sidelights to come on at the same time as the headlights.

Seems to me the easiest way to do this is to connect the signal of the headlamp switch to the signal of the sidelight switch using a diode, so that the headlamps can drive the sidelights but not vice versa.

Can anyone recommend what kind of diode I would need for the jobs? It would need to be able to take 2A or so (2x5W sidelights, 2x5W rears) at 12V.

Cheers,
Nick

theconrodkid - 7/9/08 at 06:55 PM

the rear lights come on with the sides so sides will have to be on with heads,i believe you need to have sides separate for "parking lights".
i have 2 separate switches,i took a feed from the "out" on side light switch to the "in" on headlight switch,the switch then powers main and dip relays via dip switch

nstrug - 7/9/08 at 07:13 PM

But surely if you do that, then the headlights only come on if you also have the sidelights on?

I want the following:

| Headlight | Sidelight | result
| off | off | all lights off
| off | on | sidelights only on
| on | off | all lights on
| on | on | all lights on

which requires either a 3 position rotary switch, or a diode as far as I can see.

Nick


Nick

Peteff - 7/9/08 at 09:28 PM

quote:
Originally posted by nstrug
But surely if you do that, then the headlights only come on if you also have the sidelights on?

I want the following:

| Headlight | Sidelight | result
| off | off | all lights off
| off | on | sidelights only on
| on | off | all lights on
| on | on | all lights on

which requires either a 3 position rotary switch, or a diode as far as I can see.

Nick


Nick

Just one question here.
Why would you want the headlights on with the sidelights off?
You are causing unnecessary complication by over thinking it. Power the headlights from the sidelight feed as Conrod suggests, it's the normal way to do it. Ask if anyone else has used diodes in their lighting set up. Why does it need to be a rotary switch? you could use a toggle switch or separate switches.
Do you have to switch the sidelights on first in your real car? My wife just asked this so I think she has a good grasp of what you want to do.

[Edited on 7/9/08 by Peteff]

nstrug - 7/9/08 at 10:08 PM

Maybe I'm not explaining myself properly.

I don't want the headlights on with the sidelights off - that's exactly what I want to avoid, as I thought would be clear from the logic matrix I posted.

The Dax loom uses separate feeds for the sidelights and headlights and assumes that you will use the Sierra 3-position switch.

I've ditched the 3-position switch and have separate on-off switches.

I can't run the headlights off the sidelight feed as the sidelight feed is not rated high enough.

Hence my original question.

Nick

Macbeast - 8/9/08 at 12:27 AM

1N5400 - 3A 50V PIV.

Maplins QL81C, 17p each.

My loom has nearside and offside fed and fused separately so you might have to shell out 34 p

Peteff - 8/9/08 at 09:20 AM

quote:
Originally posted by nstrug
But surely if you do that, then the headlights only come on if you also have the sidelights on?
Nick


This explanation was not very clear then Nick

You should be running your headlights through a relay so the supply is from the battery and the sidelight can supply the switching power for the relay with no real load.

nstrug - 8/9/08 at 10:41 AM

Thanks Macbeast - will do that.

I should explain, the Dax loom does not have relays for the lights - real design flaw I know.

Nick

nstrug - 9/9/08 at 11:30 PM

OK, thought about it now and suddenly occured to me that the Savage switches are DPDT - so I can just switch the sidelight circuit on the second throw of the headlight switch.

Nick

vinnievector - 10/9/08 at 12:16 AM

hi hope this helps as i to am wiring up my lights to as i can make out if you want a seperate switch for the parking lights then just a fused supply will do as for your dip and main run this through a double switch then into a relays