I have an electrical question

[riggermedic]

I installed some accessory back up lights to my M1009. They are 18 watt LED each side. If my math is correct then 1.5 amps each. I am thinking this is a bit too much to just tap into the stock back up light. I also want to add a dash switch to turn these on, but without turning on the stock back up lights or back feeding into the stock circuit.
My solution is 2 relays, 1 off the dash switch and the second off the stock back up light, both sharing a common power wire to power the lights. I am not seeing any kind of back feeding with this set up.
The other option could be 1 relay and combine the dash switch with the stock back up light and add a diode to each side so they don't back feed into each other but I have no idea of how big of a diode or where to get one
Any advice or suggestions?

 

[whatadeuce]

Old school technology calls for relays, and that woul;d be my choice.

 

[riggermedic]

bad schematic

i don't know if this helps, but it is kind of what I am thinking. I haven't really worked with diodes too much so I don't know size or rating, but its just to run a relay so not too much I would imagine

 

[MarcusOReallyus]

Either approach will work just fine. I prefer the two relay approach myself, but only because that can be connected with standard crimp terminals, no soldering required, and good quality surplus Ford 10 amp relays can be had on eBay for really cheap. I doubt if one approach is more reliable than the other.


One suggestion: If you are using standard 5 pin relays, reverse where you connect the load (lights) and where you connect B+. Why? They will work just fine your way, which is the standard approach. However, if you connect B+ to the common terminal (30), then it's supplying 12v to the exposed NC terminal (87a) any time the lights aren't on. If you connect B+ to your NO terminal (87), then 87a never sees any voltage.

Not a big deal, just a minor personal preference to avoid having a hot terminal hanging in the wind.

Fuse the whole thing at 10 amps and you're good to go.

 

[riggermedic]

Thanks

Ok so I was about to question further as I have a rudimentary understanding of these things including the terminal numbers, but I pulled up a google image and I see exactly what you are talking about. Makes perfect sense. Thanks for assist

 

[MarcusOReallyus]

Glad to help. If you figured that much out on your own you are the kind of guy who likes to learn for himself, I'm betting. Here's a GREAT resource for this kind of stuff:

http://www.the12volt.com/ohm/basics.asp


Poke around on that site and you'll be amazed at all the good info. Solid stuff.


BTW, a project like yours is on my to-do list for 3 of my vehicles, and I'll be using the two-relay approach, for reasons already mentioned. I have 8 nice off-road lights (standard incandescent) that I got for free, and I'm going to mount one as a backup light on each vehicle. I live in the country, and backing up a 200 foot driveway on a moonless night needs more than standard backup lights.

 

[riggermedic]

Thank you

I enjoy the challenge and logic involved in wiring. All too often I overthink it and come up with a workable but overly complex circuit.
Your link is quite cool, I've been spending quite a bit of time there.
Thank you

 

[PeeWeeQ]

This is a good one for relay basics...

https://www.google.com/url?sa=t&sou...9xCcVbWXgugfm9XUA&sig2=rvXc9NXTVA2IvqrF6-YY9A