Need Help, Lights, I must be dummer than most

[Casco1]

I just installed two 55watt halogens on my canopy. After reading more posts than I can remember I thought I was ready, BUT, 12 ga from battery to 12 volt 30 amp relay, off of relay (clearly marked) I get 1post to switch, 2 posts to load, 1 post to ground. From relay I cut the two load wires and install 2 15 amp inline fuses, now I run everything to the canopy and my lights and get absoletely nothing. after several hours of frustration I give up and resort to my old tried and true auto wiring. I remove the relay I tie the two hot leads directly to the battery I leave the fuses in place and go right to my switch a DPDT three position now when I push it forward my FEL lights work fine and I have the rear position for my BH lights. My question is did I do wrong by dumping the relay or am I still OK. /forums/images/graemlins/confused.gif

 

[Bob_Skurka]

The relay takes the electrical load off the switch. From what I can tell it that is really all it does (but I'm sure someone with electrical engineering experience with be able to jump in with the technical answer). I prefer to wire with a relay, and I prefer to use submersible heavy duty switches, but not everyone is as **** about being as doubly safe as I am. Worst case, you might blow a switch out every once in a while without the relay, but it probably won't be any more serious than that. And that is not tragic.

 

[timb]

In basic terms, the biggest advantage of a relay-controlled circuit is being able to control a heavy-power circuit with a light-duty switch and control wiring. Fancier relays may bring other benefits in bizarre uses but nothing you're likely to need in a simple lighting circuit. If your switch and wiring can handle the full power load, if you're not over-fused, then you'll be ok.

 

[Casco1]

Thanks for the quick reply. with the relay in place I had no juice at all no matter what I did. My switch is rated at 30 amps my hot leads are 14 GA I used crimp connectors as I thought soldering was overkill.

 

[timb]

Your switch is plenty heavy - and the wire can handle the load (14ga is good for 15 amps DC) - but depending on how you ran the wiring conductors and how long they are - you could end up being down a bit on voltage (and light output). Probably not enought to get too worried about though.

In the TMI (too-much-info) category:

The voltage drop = amps*distance/volts * 1/resistance factor of wire.

Quick and dirty example -

Both lights together should draw around 8.2 amps @ 13.5v. So 8.2 amps * 15 feet of wire / 13.5 volts @ 14ga wire resistance (assuming copper) ...the voltage drop should equal just over 1/2 volt or a little under 5%. Not huge, but keep your runs as short as you can. Some lighting types are touchier than others on how much light output falls as voltage droops.

 

[Soundguy]

That relay is a money saving device.. it lets you run lesss heavy gauge wire.. as in.. your heavy gauge wire can run right from the battery ( or power connection point ) and then right to the lamp.. with the relay inline at a convienient spot in order to run the switch wireing.

Relay is just a magnetic switch.. the 4 post 30 amp automotive jobs have two contacts for the load.. that is the switch.. battery to one of them, the other side to the lamp. The other two contacts.. you say one is ground.. that leaves the 4th contact for switched power. A simple toggle or push button switch wired from that same hot load side, thru a switch, to the 4th contace will fix you up. Doesn't get much easier for electronics than that.

While a split fues.. one for each lamp is ok.. I thing the preferable method would be one large fuse or breaker rated for the desired load, connected as close as possible to the power source. That way if you get frayed wireing before the switch and lamps.. the fuse protects everything downline.... and keeps feet of wire from burning.

Soundguy

 

[Casco1]

Thanks again for your input. /forums/images/graemlins/smile.gif

 

[NY_Yankees_Fan]

I need your help too.

I am going to wire my new Sims cab and I am not sure how to do it from a wiring size relay point of view. I plan to have 2- 55 lights in the front and 2-55 lights in the rear with a flashing light unit on the roof and a windshield wiper. I have upgraded to the high output alternator so I should have enough amps to run it. I plan on installing a box with a light switch for both front lights, a separate switch for the rear lights and one switch for the light for a total of 3 switches. I think the windshield wiper has a switch on the unit itself, if not that would the 4th switch.

I am thinking running one wire to supply the box and then using that power to feed all switch/circuits. I want to be able to take the cab off in the summer so I want to disconnect the least amount of connections. Here are my questions.

1.Best place to connect? Direct to the battery or to the extra circuit under the set, or another place??
2.Size of the wire feeding the box? 12 gauge home wire work?
3.Do I need a relay? If so, the size and where does it go, on the line feeding the light box?

If you can think of a better way to do this please let me know.

Thanks for your help. Happy HO HO /forums/images/graemlins/grin.gif

 

[PineRidge]

Here is a diagram that just may help you.

 

[NY_Yankees_Fan]

Should I use a relay on each switch or just one relay that feeds all switches?