Wiring up switches... Dual?

I thought about posting this on HIDplanet and Candlepower, but ultimately I figured since it's on my jeep I'll post it here. 5-90, Fitch, and all electrical guru's chime in...

I'm looking to hook up my switchbox to two seperate control sources. I have the idea in my head but I'm over-confusing myself when it comes to wiring the relays. I want to make 1 of my 6 switches control which control device turns them on/off. Sounds confusing right? Well think of it this way - switch 1 is the main switch, 2-6 are all hooked up to aux lights. When switch 1 is in the up position, the headlight high beam switch controls ALL the others. So with high beams on, all the lights come on. With it off, they all turn off. Then, flip the main switch number 1 down, and all the others operate independently. High beam or no high beam. I'm not sure which type of relay to use, I'm thinking SPDT? One for the main switch, and one somewhere else in between it and the high beam switch? I think I need to spend a few hours studying the FSM and designing some wiring diagrams...

That sound pretty easy to me. Your relay for sw 1 you would use the center blade to run power to the relays, which is basicly bypassing the first relay and goes to power the switches of the remaining ones, then then triggered side of the first relay would be the coil trigger for the remaining relays from the highbeam side of the lights.

In theory,
sw1 off power travels thru relay one to the remaining switches for ind. use
sw2-6 have power to trigger relays for lights

sw1 on highbeams off no aux lights
sw1 on HB on allaux lights on

uggghhh I've been trying to draw up some diagrams all night and can't seem to get it right. Ultimately I just keep ending up with power being determined at the aux switches anyways. Whether switch one is on or off.

Look up a "Logical OR" circuit, and expand as required.

The "OR" would be switch one to tie to headlamps OR release to independent function (turning on switch #1 would engage all the relays, turning it off would free them up individually.)

You'd need diodes in the switch box to prevent the switches from backfeeding each other - a diode is essentially a "one-way valve" or a "check valve" for electricity, it only allows current flow in one direction.

You won't need a special relay to do that - it's all in the wiring of the switches. You can use standard SPDT relays (or, if you want to separate pairs of lights to individual circuits, you use DPST relays, which are slightly less common than the typical SPDT. Of course, an SPDT may be used as an SPST by simply not connecting anything to 87a.)

Something akin to this - http://www.allaboutcircuits.com/vol_3/chpt_3/10.html - but rearrange it slightly so that each light will turn on if the Master switch is on OR the individual switch is on. Make sense?

Don't use the Logical AND section - that requires that both switches be on in order to have the light on. Logical AND is how safeties are wired - there's an "Arm" switch to power the system, then the trigger switch (rather like a nitrous setup - there's the "arm" switch that is somewhere inconvenient to reach or takes a key, and the "fire" switch is on the steering wheel or the shifter knob.)

Concantenation of Logical AND and Logical OR is how integrated circuits are made - you're actually putting together the building blocks of a digital computer! With a half-dozen inputs, you could go either way (use a multiplexed OR IC or build your own from discrete components,) but if I were doing anything complex I'd start looking at CMOS chips to keep things easy, and just etch a board (you can build the diode gate on a perfboard, or probably even "wire it loose" if you're so inclined.)

Anyhow, what you end up with is five OR circuits, with a common input (let's say it's input A) provided by the Master switch and the separate input (input B) provided by each switch. The output of an OR is true ("on") if EITHER input A OR input B is true ("on".)

Look at the link, think it over, and see if it makes sense to you.

Almost forgot - tap the headlamp lead for the power for the Master switch - that will have the lamps come on when you turn the headlamps on, IF the Master switch is on (if all switches are off, the lamps will all be OFF, if you've wired it up properly.)

ahhh well that's very reassuring. This whole time I was thinking there's got to be more to this otherwise current is going to be running backstream! Thanks a ton, I'll read it over and report back with a few diagrams to critique.

Ok I've been drawing a few setups, but do I need two accessory leads coming out from the relays going to all my lights?

DanMan2k06 said:

Ok I've been drawing a few setups, but do I need two accessory leads coming out from the relays going to all my lights?

Click to expand...

No reason to, really. Take one lead out (from Pin 87 - Pin 30 is for power input,) and split it in two. Wire the lamps in parallel (this gives them both full voltage, instead of 6V to each.)

Ok I'm kind of understanding it now, but how do I completely bypass the switches when the main switch is off? So that all the relay input signals are now relying on the signal from coming from the high beam switch? Is this where the diodes come in?

Well after spending about 4 hours studying this stuff and drawing about 10 pages of schematics and theory, it is just not possible. Easily that is. I would have to combine an OR and a NOR circuit, make a small board with lots of tiny soldering, just all kinds of stuff that really isn't worth doing for the results lol. So 5-90 thanks for the responses, if you can find an easier way to do it, feel free to post up haha.

I believe this can be easily done with one relay associated with the high beams and SPDT switches for the aux lights. What I'm not sure about is if you want to be able to turn the individual aux lights off while the high beams are on?

I don't think this would be a problem but may as well take into consideration from the get-go.

In rereading this I see that my question wasn't pertinent. You say you want all lights on with the high beams. The pertinent question is how to turn all aux lights off with high beams off while in the "high beam control" mode. Right now I see two alternatives: use two standard automotive relays (SPDT) or go down to Radio Shack and get a DPDT relay for a few bucks. I will play with this a bit more and see if I can come up with another solution.

For the master switch, I would probably use a DPDT on-on-center off toggle with up being high beam control, center all aux lights off and down individual control.

For the individual aux lights use a SPDT with the common terminal to the relay coil and one terminal to a constant plus and the other to the master switch.

In rereading this I see that my question wasn't pertinent. You say you want all lights on with the high beams. The pertinent question is how to turn all aux lights off with high beams off while in the "high beam control" mode. Right now I see two alternatives: use two standard automotive relays (SPDT) or go down to Radio Shack and get a DPDT relay for a few bucks. I will play with this a bit more and see if I can come up with another solution.

For the master switch, I would probably use a DPDT on-on-center off toggle with up being high beam control, center all aux lights off and down individual control.

For the individual aux lights use a SPDT with the common terminal to the relay coil and one terminal to a constant plus and the other to the master switch.

I am ensuring that all aux lights are off in the "headlight" mode by interrupting the negative side of the circuit. I don't see any way to do this offhand without a separate set of contacts (i.e. DPDT relay) or a second standard relay. No big deal since relays are dirt cheap but it's one more component to find a place for.

I will post a schematic when I learn how. Will have to get a tutorial from my wife I guess.

Yea that's what I was trying to avoid, having to wire in 6 more relays and find room.

I finally learned how to post images (I think). I did this on my own and it seems to work but may not be the most sophisticated way to do it. If it looks like you can use the circuit, you can print it out and get rid of some of that godawful advertising.



I think this accomplishes what you wanted and uses only one additional component in addition to those that you will normally use to switch the aux lights -- one standard automotive relay that is triggered by the high beam headlight. Of course, it also calls for the master DPDT switch that you were planning to use anyway.

Note that I show relay coils for the individual lighting circuits in the diagram because I assume you will be using them but the circuit works the same with or without relays. The only essential difference in wiring the the basic lighting circuit involves running the common negative wiring to the master switch.

With the master switch in the up position, plus voltage is applied to both sides of the SPDT switches and all aux lamps will light regardless of the switch positions as long as high beams are on. Switching to low beams drops the new relay out and interrupts the common negative side of the individual lighting relays, turning all aux lights off.

With the master switch in the down position, the negative ground circuit is restored and plus voltage is applied to only one side of the aux lamp switches which can then be used to individually control those lamps.

I mentioned a center off mode for the master switch. If a center off switch is available in the style of switch you select, and you want that feature, all aux lights can be switched off quickly with the master. Normally not a big deal but there if you want it.

I believe this will work as drawn but let me know if I've missed anything. I take no offense if someone finds a flaw or a better way -- the perfect circuit has yet to be designed.

The perfect circuit doesn't need to be designed because it can design and diagnose itself lol.

I'll take a look at the pic when I get home, I'm on my phone now. But thanks for taking the time to try an figure it out!