Any electrical gurus here?

[Toecutter]

I need to add a front mounted floodlight to BCS tractor (12v DC system, with a Honda 390) , for winter duty. It's pitch black when i get up and it's pitch black when I head home at the end of day.

A "headlamp" is useless, as it ends up illuminating the snow being thrown, and not the ground in front of the snowthrower. So, my idea is for a pedestal mount LED floodlight (draws 1.5 amps) on a magnetic base, attached to the housing of the snowthrower, ahead of the cloud of thrown snow.

With a draw this low... do I still need a relay? Or can I simply wire "battery > fuse > switch > Light > ground"?


Also, for the inline fuses, if I go with the relay... I require a 2 amp for the light, but what should I be using for the switch? Also... aside from accidentally leaving the switch on.. are there any issues with drawing power directly from the battery?

I hope this makes sense. if it doesn't, I'll try to clarify a bit better.

[RinkRat II]

     With a draw that low, your on the right track not using a relay.  Properly fused as you've indicated will work just fine and be sure your components are rated above your amp draw.

       Paul B

[Rick in WNY]

Toecutter,

Last question first... no, wiring directly off the battery is not a problem, provided you add a fuse as you've already mentioned.

At a draw of 1.5 amps, as long as the wire you're using is 16ga or bigger, no worries. And 16 ga is rated to 10 amps, but I tend to not go smaller than 16 because it gets harder to work with in my experience. As long as the switch is rated for more than 2 amps, you're good to go. A 20 amp switch would be overkill, but work just fine on a 2 amp circuit. The reverse is not the case.

So, for what you're doing, if you start with the battery, connect it thusly:

Battery positive - fuse - switch - light - wire back to battery negative.

After that, the only bugaboo you may see is that LED lights are polarity sensitive... hook them up backwards and they will not light up.

Good luck and keep us posted!

Rick

[Toecutter]

Thankyou, gents, 12 gauge wire throughout.


For future knowledge... at what point should one consider using a relay?

[Wayne Orwig]

No relay needed.
Just go from the battery, to a fuse, to a switch, to the light. A relay might be handy so it is switched with another circuit though.

A rather interesting advantage with most LED lights is that they do not care (much) about the voltage. They regulate it at the light. So you can use some pretty wimpy wire gauge and not reduce the light output.

What I do, for installs like that, is go to the local hardware store and buy some twin lead, like would be used for lamp cord. I would be more concerned with getting a heavy duty enough insulation for durability, and not worried about the wire gauge. There is a 'rib' on one side of the lamp cord so you can trace the polarity easily enough.

[RinkRat II]

    Generally as a rule, anytime the load exceeds the rating of the switch it's best to use a relay rated higher than the load. Plus relays look cool and your  friends will think your a genius 

      Paul B 

[Moto]

Wayne's advice is good. If you want a nicer two-wire insulated cable than lamp cord, you can find it at a boating supplies store, sold by the foot or meter. (It is cable of two (or three) insulated wires surrounded by another insulating sleeve.)

[Toecutter]

Ok... one other question...

Should the switch be grounded to the frame?

[RinkRat II]

  Not required.
   
     Paul B

[Wayne Orwig]

at what point should one consider using a relay?

If the switch or wiring needs to be, or is, rated for too few amps, then a relay can provide more current ability. If you can add a large enough switch and wires, a relay may not be needed. Often a motorcycle headlight switch and wire is too marginal for a even the factory headlight load. A relay can move the load to better wiring.

A relay can also act as a remote switch. Put a small switch on a long wire, and trip a relay that is near the battery and load. On the other hand, Guzzi installed a remote starter relay, so the start button tripped a small relay coil under the seat. Sounds good. But they fed the relay contact with 'long distant' power from the ignition switch and wire harness. If the relay contact was fed with battery power, we would have never head the term 'startus interruptus'.

Plus you can do logic with a relay, such as, when power is applied to the starter, then the headlight is turned OFF. Turning ON a sidestand switch, might turn OFF the ignition. That type thing.

[Aaron D.]

Your BCS has a battery?